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Biochemistry 4th Edition by Donald Voet – Test Bank
 
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Chapter 3: Nucleotides, Nucleic Acids, and Genetic Information

 

Matching

 

A) diploid
B) phosphodiester
C) probe
D) pyrimidine
E) introns
F) cloning
G) transformed
H) exons
I) ampicillin
J) autoradiography
K) chain-terminator
L) purine
M) ester

 

  1. Cytosine, uracil, and thymine are derivatives of ______.

Ans:  D

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

  1. Nucleic acids are composed of nucleotides that are linked by ______ linkages.

Ans:  B

Section 3.2.A

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

  1. Organisms composed of cells with two sets of chromosomes are called ______ organisms.

Ans:  A

Section 3.3.A

Difficulty:  Easy

Learning Objective: Overview of Nucleic Acid Function

 

  1. Eukaryotic genes often contain regions that are transcribed and later excised from the RNA, called ______.

Ans:  E

Section 3.5.D

Difficulty:  Moderate

Learning Objective: Overview of Nucleic Acid Function

 

  1. Experiments by Avery and colleagues proved that DNA was the substance that _____ a non-pathogenic pneumococcus strain into a virulent strain.

Ans:  G

Section 3.3.A

Difficulty:  Moderate

Learning Objective: Overview of Nucleic Acid Function

 

  1. The method that Sanger developed for DNA sequencing using dideoxy nucleotides is called the ______ method.

Ans:  K

Section 3.4.C

Difficulty:  Easy

Learning Objective: Nucleic Acid Sequencing

 

  1. Plasmids are small, circular DNA molecules that are used in ______.

Ans:  F

Section 3.5.A

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

  1. Certain plasmids contain genes that confer resistance to ______.

Ans:  I

Section 3.5.A

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

  1. A small fragment of labeled DNA or RNA used in a hybridization experiment is called a ______.

Ans:  C

Section 3.5.B

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

  1. After hybridization, the fragment of interest can be detected by ______.

Ans:  J

Section 3.5.B

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

Multiple Choice

 

  1. Nucleotides play a central role in living organisms because
  2. A) they mediate transport of energy within the cell.
  3. B) they are involved in oxidation-reduction reactions.
  4. C) they are involved in intracellular signaling.
  5. D) they function as building blocks for nucleic acids.
  6. E) all of the above

 

Ans:  E

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

 

  1. Which of the following statements about nucleotides is false?
  2. A) Nucleotides mediate transport of energy within the cell.
  3. B) Nucleotides are involved in oxidation-reduction reactions.
  4. C) Nucleotides store genetic information.
  5. D) Nucleotides are involved in biosynthetic reactions.
  6. E) none of the above

 

Ans:  C

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

 

  1. What group is attached to the pyrimidine ring in thymine and is not present in uracil?
  2. A) ribose
  3. B) —CH3
  4. C) NH2
  5. D) deoxyribose
  6. E) none of the above

 

Ans:  B

Section 3.1

Difficulty:  Moderate

Learning Objective: Nucleotides

 

  1. The molecule shown in the diagram is a

 

 

  1. A)
  2. B)
  3. C)
  4. D)
  5. E) none of the above

 

Ans:  E

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

  1. What is the name of the molecule shown in the diagram?

 

  1. A) adenosine
  2. B) cytosine
  3. C) cytidine
  4. D) cytidine monophosphate
  5. E) uridine

 

Ans:  C

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

 

  1. Nucleotides contain one or more phosphate groups that are usually attached to the:
  2. A) C3¢ or C5¢ atoms
  3. B) C3 or C3¢ atoms
  4. C) C5 or N3 atoms
  5. D) C1¢ or N3 atoms
  6. E) none of the above

 

Ans:  A

Section 3.1

Difficulty:  Moderate

Learning Objective: Nucleotides

 

  1. ‘AMP’ is used to refer to
  2. A)
  3. B) adenylic acid.
  4. C) adenomethyl purine.
  5. D)
  6. E) all of the above

 

Answer:  B

Section 3.1

Difficulty:  Difficult

Learning Objective: Nucleotides

 

 

  1. Inside our cells, free nucleotides are almost always associated with ______.
  2. A) proteins
  3. B) cholesterol
  4. C) Cl counterions
  5. D) fatty acids
  6. E) Mg2+ counterions

 

Answer:  E

Section 3.1

Difficulty:  Moderate

Learning Objective: Nucleotides

 

 

  1. Humans typically recycle approximately _____ of ATP each day.
  2. A) 50 kg
  3. B) 50 mg
  4. C) 50 g
  5. D) 50 mg
  6. E) 500 kg

 

Answer:  A

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

  1. Nucleoside triphosphates are useful for energy transfer because the phosphoanhydride bonds are relatively ______.
  2. A) stable
  3. B) high energy
  4. C) biocompatible
  5. D) large
  6. E) low energy

 

Answer:  B

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

 

  1. Nucleoside triphosphates carry energy in the form of
  2. A) glycosidic bonds
  3. B) phosphoester bonds
  4. C) phosphoanhydride bonds
  5. D) hydrogen bonds
  6. E) amide linkages

 

Answer:  C

Section 3.1

Difficulty:  Moderate

Learning Objective: Nucleotides

 

 

  1. The major carrier of energy in the cell is:

 

  1. A) adenosine monophosphate
  2. B) adenosine diphosphate
  3. C) adenosine triphosphate
  4. D) adenosine tetraphosphate
  5. E) flavin adenine dinucleotide

 

Answer:  C

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

  1. Which of the following nucleotides contain energy rich bonds?
  2. A) ATP
  3. B) TTP
  4. C) GTP
  5. D) CTP
  6. E) all of the above

 

Answer:  E

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

 

  1. Which of the following molecules does not contain an energy rich phosphoanhydride bond?
  2. A) ADP
  3. B) GDP
  4. C) AMP
  5. D) CDP
  6. E) all of the above

 

Answer:  C

Section 3.1

Difficulty:  Easy

Learning Objective: Nucleotides

 

 

  1. By convention, the sequence of nucleotide residues in a nucleic acid is written ___________ starting with the ____ end.
  2. A) left to right; 3¢
  3. B) right to left; 3¢
  4. C) left to right; 5¢
  5. D) right to left; 3¢
  6. E) top to bottom; 3¢

 

Answer: C

Section 3.2.A

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

  1. Chargaff’s rules state that:
  2. A) The amount of guanine plus cytosine in mammalian genomes varies from about 39 to 46%.
  3. B) DNA is always double stranded and RNA is always single stranded.
  4. C) DNA contains two grooves, a major groove and a minor groove.
  5. D) In DNA the number of adenine residues is identical to the number of thymine residues and the number of guanine residues is identical to the number of cytosine residues.
  6. E) DNA contains two strands that run in opposite directions.

 

Answer: D

Section 3.2.B

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

 

  1. Which of the following bases pairs with guanine?

 

 

Answer:  E

Section 3.2.B

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

  1. The Watson and Crick model of a double-helical structure for DNA was based, in part, on evidence from
  2. A) NMR (nuclear magnetic resonance) spectroscopy.
  3. B) IR (infrared) spectroscopy.
  4. C) atomic force microscopy.
  5. D) electron microscopy.
  6. E) X-ray diffraction .

 

Answer:  E

Section 3.2.B

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

 

  1. Knowledge about the tautomeric forms of the bases of nucleic acids is needed
  2. A) to understand H-bonding between the complementary bases
  3. B) to understand how the bases are linked to ribose.
  4. C) to understand how bases are linked to deoxyribose.
  5. D) to understand the ability of nucleotides to act as energy carriers.
  6. E) to distinguish the 5’-end of a DNA strand from the 3’-end.

 

Answer:  A

Section 3.2.B

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

 

  1. Nucleotides in a DNA molecule are linked together through
  2. A) glycosidic bonds.
  3. B) amide linkages.
  4. C) hydrogen bonds.
  5. D) phosphoanhydride bonds.
  6. E) phosphodiester bonds.

 

Answer:  E

Section 3.2.B

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

  1. A double stranded DNA fragment contains 12% adenine residues. Calculate the percentage cytosine residues.
  2. A) 12%
  3. B) 24%
  4. C) 38%
  5. D) 50%
  6. E) 78%

 

Answer:  C

Section 3.2.B

Difficulty:  Moderate

Learning Objective: Introduction to Nucleic Acid Structure

 

 

  1. Which of the following bases is not present in RNA?

 

 

Answer:  D

Section 3.2.C

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

  1. RNA occurs primarily as single stranded molecules that can give rise to _______ structures.
  2. A) diploid
  3. B) stem-loop
  4. C) parallel
  5. D) tautomeric
  6. E) haploid

 

Answer:  B

Section 3.2.C

Difficulty:  Easy

Learning Objective: Introduction to Nucleic Acid Structure

 

 

  1. In 1944 Avery, MacLeod, and McCarty did experiments with Diplococcus pneumoniae that proved that
  2. A) DNA is double stranded.
  3. B) DNA contains deoxyribose.
  4. C) DNA can be transcribed into RNA.
  5. D) DNA can permanently transform a non-pathogenic strain into a pathogenic strain.
  6. E) The structure of DNA provides a mechanism for reliable replication.

 

Answer:  D

Section 3.3.A

Difficulty:  Easy

Learning Objective: Overview of Nucleic Acid Function

 

 

  1. In living organisms, genetic information is most often stored in the form of
  2. A) ribonucleic acid.
  3. B) deoxyribonucleic acid.
  4. C)
  5. D)
  6. E)

 

Answer:  B

Section 3.3.A

Difficulty:  Easy

Learning Objective: Overview of Nucleic Acid Function

 

  1. It is impossible for RNA to store genetic information, because
  2. A) RNA does not base pair and therefore cannot be replicated.
  3. B) enzymes cannot process genetic information in the form of RNA.
  4. C) RNA forms complex folded structures.
  5. D) RNA is very unstable.
  6. E) None of the above answers is correct; RNA can store genetic information.

 

Answer:  E

Section 3.3.A

Difficulty:  Difficult

Learning Objective: Overview of Nucleic Acid Function

 

 

  1. Genomic DNA is ______, resulting in the production of _________.
  2. A) transcribed; mRNA
  3. B) translated; tRNA
  4. C) transcribed; protein
  5. D) translated; protein
  6. E) translated; rRNA

 

Answer:  A

Section 3.3.B

Difficulty:  Moderate

Learning Objective: Overview of Nucleic Acid Function

 

 

  1. Which of the following nucleic acids provides the key to decoding genetic information?
  2. A) tRNA
  3. B) rRNA
  4. C) mRNA
  5. D) DNA
  6. E) None of the above

 

Answer:  A

Section 3.3.B

Difficulty:  Difficult

Learning Objective: Overview of Nucleic Acid Function

 

  1. Which diagram depicts correctly a ribosome engaged in translation?

 

 

 

A.) a

B.) b

C.) c

D.) d

 

Answer:  A

Section 3.3.B

Difficulty:  Difficult

Learning Objective: Overview of Nucleic Acid Function

 

 

  1. Transfer RNA molecules are involved in
  2. A)
  3. B)
  4. C)
  5. D) reverse transcription.
  6. E) posttranslational processing.

 

Answer:  B

Section 3.3.B

Difficulty:  Easy

Learning Objective: Overview of Nucleic Acid Function

 

  1. Which of the following DNA sequences is considered palindromic?
  2. A) AAGCTT
  3. B) GAACTT
  4. C) GAACAA
  5. D) AAGCAA
  6. E) AAGTTC

 

Ans:  A

Section 3.4.A

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

 

  1. Which of the following DNA sequences (in which N is any nucleic acid residue) is palindromic?
  2. A) ANAGCTT
  3. B) AANGCTT
  4. C) AAGNCTT
  5. D) AAGCNTT
  6. E) AAGCTNT

 

Ans:  C

Section 3.4.A

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

 

  1. Double stranded DNA molecules can be cleaved at specific recognition sites by
  2. A) RNA polymerase.
  3. B) DNA ligase.
  4. C) DNA polymerase.
  5. D) reverse transcriptase.
  6. E) Type II restriction endonucleases.

 

Answer:  E

Section 3.4.A

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

  1. Which of the restriction enzymes listed in the table below produces blunt-end fragments?

 

Enzyme Cleavage site
AluI AG$CT
HindIII A$AGCTT
BamHI G$GATCC
EcoRI G$AATTC
BglII A$GATCA
  1. A) AluI
  2. B) BamHI
  3. C) BglII
  4. D) EcoRI
  5. E) HindIII

 

Answer:  A

Section 3.4.A

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

 

  1. Which of the enzymes listed in the table below produce identical sticky ends?

 

Enzyme Cleavage site
AluI AG$CT
HindIII A$AGCTT
BamHI G$GATCC
EcoRI G$AATTC
BglII A$GATCA
  1. A) AluI and HindIII
  2. B) AluI and BamHI
  3. C) HindIII and EcoRI
  4. D) HindIII and BglII
  5. E) BamHI and BglII

 

Answer:  E

Section 3.4.A

Difficulty:  Difficult

Learning Objective: Nucleic Acid Sequencing

 

  1. Gel electrophoresis generally separates nucleic acids on the basis of
  2. A)
  3. B)
  4. C)
  5. D) charge-density.
  6. E) none of the above

 

Ans:  C

Section 3.4.B

Difficulty:  Easy

Learning Objective: Nucleic Acid Sequencing

 

 

  1. DNA sequencing using the Sanger method requires
  2. A) template, primer, DNA polymerase, mRNA, dNTPs, ddNTPs.
  3. B) template, primer, DNA polymerase, dNTPs, ddNTPs.
  4. C) template, primer, DNA polymerase, rRNA, dNTPs, ddNTPs.
  5. D) template, primer, DNA polymerase, mRNA, dNTPs.
  6. E) none of the above

 

Ans:  B

Section 3.4.C

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

 

  1. In Sanger dideoxy DNA sequencing, DNA polymerase I is used to add nucleotides to the ___ end of the growing polynucleotide chain.
  2. A) sticky
  3. B) blunt
  4. C) 3¢
  5. D) 5¢
  6. E) dideoxy nucleotide containing

 

Answer:  C

Section 3.4.C

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

  1. DNA sequencing by the chain-termination method utilizes DNA polymerase I to make a complementary copy of the target or template DNA molecule. A reaction with a 20 bp template and dideoxyadenosine nucleotides as terminators results in the production of a 5 bp fragment.  Based on this result, we can conclude that the template contains
  2. A) a cytosine at position 5.
  3. B) a thymine at position 5.
  4. C) a cytosine at position 16.
  5. D) a thymine at position 16.
  6. E) a uracil at position 5.

 

Answer:  D

Section 3.4.C

Difficulty:  Difficult

Learning Objective: Nucleic Acid Sequencing

 

 

  1. DNA fragments are usually inserted into a plasmid vector and cloned before they are analyzed by chain termination sequencing because
  2. A) DNA fragments need to be pure in order to obtain an unambiguous sequence.
  3. B) a large number of identical fragments is needed in a sequencing reaction in order to generate detectable amounts of products.
  4. C) plasmid vectors have known sequences that can be used for design and annealing of the primer oligonucleotides, which are used to initiate the sequencing reaction.
  5. D) all of the above
  6. E) none of the above

 

Answer:  D

Section 3.4.C

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

 

  1. Which of the following conclusions about the human genome is (are) true?
  2. A) Only about 80% of the human genome is transcribed to RNA.
  3. B) Only about 1-2% of the human genome codes for proteins.
  4. C) Most of the proteins found in humans are also found in many other animals.
  5. D) Nearly half of the human genome consists of repetitive DNA sequences.
  6. E) All of the above.

 

Ans:  E

Section 3.4.D

Difficulty:  Difficult

Learning Objective: Nucleic Acid Sequencing

 

  1. Which of the following conclusions about the human genome is false?
  2. A) Only about 80% of the genome is transcribed to RNA.
  3. B) Most of the proteins found in humans are unique to vertebrates.
  4. C) Nearly half of the human genome consists of repetitive DNA sequences.
  5. D) The genomes of any two people are likely to be 99.9% identical
  6. E) None of the above

 

Ans:  B

Section 3.4.D

Difficulty:  Difficult

Learning Objective: Nucleic Acid Sequencing

 

 

  1. Alterations in genetic information can be caused by
  2. A) mistakes made during replication.
  3. B) faulty recombination.
  4. C) transposition of genes.
  5. D) damage caused by chemicals or radiation.
  6. E) all of the above

 

Ans:  E

Section 3.4.E

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

 

  1. Alterations in genetic information cannot be caused by
  2. A) mistakes made during replication
  3. B) faulty recombination.
  4. C) transposition of genes.
  5. D) mistakes made during translation.
  6. E) all of the above

 

Ans:  D

Section 3.4.E

Difficulty:  Moderate

Learning Objective: Nucleic Acid Sequencing

 

  1. Mutations leading to changes that can be inherited by the next generation have to be introduced into at the _______ level.
  2. A) DNA
  3. B) rRNA
  4. C) protein
  5. D) mRNA
  6. E) tRNA

 

Answer:  A

Section 3.4.E

Difficulty:  Easy

Learning Objective: Nucleic Acid Sequencing

 

 

  1. The production of multiple identical organisms from a single ancestor is called ________.
  2. A) DNA ligation
  3. B) phenotyping
  4. C) cloning
  5. D) transcription
  6. E) sequencing

 

Answer:  C

Section 3.5.A

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

 

  1. Small circular DNA molecules used to carry foreign DNA fragments are called ________.
  2. A) mRNAs
  3. B) bacteriophage
  4. C) clones
  5. D) plasmids
  6. E) nucleotides

 

Answer:  D

Section 3.5.A

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

  1. In molecular cloning, transformed organisms must be identified. One common method for accomplishing this involves the inclusion of ________ in the plasmid.
  2. A) a restriction site
  3. B) a nuclease gene
  4. C) a deletion
  5. D) an origin of replication
  6. E) an antibiotic resistance gene

 

Answer:  E

Section 3.5.A

Difficulty:  Moderate

Learning Objective: Manipulating DNA

 

 

  1. A genomic library
  2. A) is a collection of protein structures from a specific organism.
  3. B) is a collection of cloned DNA fragments representing all of an organism’s DNA.
  4. C) contains only protein-coding DNA sequences.
  5. D) is best constructed from very short DNA fragments.
  6. E) is built from mRNA by reverse transcription.

 

Answer:  B

Section 3.5.B

Difficulty:  Moderate

Learning Objective: Manipulating DNA

 

 

  1. Radioactively labeled, single-stranded oligonucleotides are often used in in situ hybridization. Which of the probes listed below would work best, when probing for a RNA molecule containing the sequence 5¢-AGCTAACGGG-3¢?
  2. A) 5¢-AGCTAACGGG-3¢
  3. B) 5¢-GGGCAATCGA-3¢
  4. C) 5¢-CCCGTTAGCT-3¢
  5. D) 5¢-TCGATTGCCC-3¢
  6. E) all of the above

 

Answer:  C

Section 3.5.B

Difficulty:  Moderate

Learning Objective: Manipulating DNA

 

  1. In order to perform PCR, which of the following describes the reagents that must be included in the reaction mixture?
  2. A) DNA fragment, primers flanking the region of interest, dNTPs, DNA polymerase
  3. B) DNA fragment, primers flanking the region of interest, dNTPs, ddNTPS, DNA polymerase
  4. C) DNA fragment, one primer, dNTPs, DNA polymerase, DNA ligase
  5. D) DNA fragment, primers flanking the region of interest, dNTPs, DNA Ligase
  6. E) none of the above

 

Ans:  A

Section 3.5.C

Difficulty:  Moderate

Learning Objective: Manipulating DNA

 

 

  1. Which of the following statements about PCR is (are) true?
  2. A) Small amounts of DNA can be easily amplified to millions of copies.
  3. B) PCR is often used in forensics laboratories.
  4. C) PCR reaction products can be used in molecular cloning.
  5. D) PCR is used in clinical laboratories.
  6. E) All of the above.

 

Ans:  E

Section 3.5.C

Difficulty:  Difficult

Learning Objective: Manipulating DNA

 

 

  1. DNA polymerase from Thermus aquaticus is used in PCR because
  2. A) it is a soluble protein.
  3. B) the genes from Thermus aquaticus are readily distinguished from those of ‘normal’ organisms.
  4. C) the enzyme is readily deactivated by heat, effectively halting the reaction.
  5. D) it is stable at high temperatures.
  6. E) it is not infectious.

 

Answer:  D

Section 3.5.C

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

  1. A gene knockout is
  2. A) a gene that has been inactivated or removed from an organism.
  3. B) a dominant gene that knocks-out expression of other genes.
  4. C) a gene inserted in place of another gene.
  5. D) a gene present on a YAC.
  6. E) none of the above

 

Ans:  A

Section 3.5.D

Difficulty:  Moderate

Learning Objective: Manipulating DNA

 

 

  1. Recombinant DNA technology can be used for
  2. A) constructing mutant proteins.
  3. B) the industrial production of useful proteins.
  4. C) producing transgenic organisms.
  5. D) correcting genetic defects.
  6. E) all of the above

 

Answer:  E

Section 3.5.D

Difficulty:  Easy

Learning Objective: Manipulating DNA

 

Short Answer

 

  1. This is the structure of adenine.

 

 

  1. Is adenine a purine or a pyrimidine?
  2. Which base does adenine base-pair (H-bond) with in DNA?
  3. What is the name of the molecule that is composed of adenine linked to the C1’ of ribose?
  4. Indicate on the drawing through which atom adenine is connected to ribose or deoxyribose.
  5. Indicate on the drawing which groups on adenine are involved in base-pairing or H-bonding with its complementary base.

Ans:  a.  purine

  1. thymine
  2. adenosine
  3. see diagram
  4. see diagram

Level of Difficulty:  Difficult

Section 3.2

Learning objective: Introduction to Nucleic Acid Structure
67.  This is the structure of cytosine.

 

 

  1. What are the names of the other three bases that are found in DNA.
  2. Is cytosine a purine or a pyrimidine?
  3. Give the name and the one letter abbreviation of the base cytosine base-pairs (H-bonds) with in DNA?
  4. Indicate on the drawing through which atom cytosine is connected to ribose or deoxyribose.
  5. What is the name of the molecule composed of cytosine linked to ribose?
  6. Indicate on the drawing which groups on cytosine are involved in base-pairing (H-bonding) with its complementary base.

 

Ans:  a.  adenine, guanine, and thymine

  1. pyrimidine
  2. guanine, G
  3. cytidine
  4. see diagram
  5. see diagram

Level of Difficulty:  Difficult

Section 3.2

Learning objective: Introduction to Nucleic Acid Structure

 

  1. Describe the structure of a DNA molecule by listing 6 characteristics.

 

Ans:     1.  DNA forms a double helix

  1. the two strands run anti-parallel
  2. the sugar is deoxyribose
  3. the sugar-phosphate groups are on the outside of the helix
  4. the bases are in the center of the helix
  5. the bases are planar and their plane is orientated perpendicular to the axis of the helix
  6. there are four bases: Adenine, Guanine, Cytosine and Thymine
  7. The strands are held together by H-bonding between complementary bases: Adenine-   Thymine and Guanine-Cytosine
  8. The helix has a minor and a major groove on its surface.

Level of Difficulty:  Difficult

Section 3.2

Learning objective: Introduction to Nucleic Acid Structure

 

  1. Describe the central dogma of molecular biology (to do this draw a diagram of the central dogma and describe all the arrows).

 

Ans:

Level of Difficulty:  Difficult

Section 3.3B

Learning objective: Overview of Nucleic Acid Function

 

  1. There are three types of RNA that are directly involved in translation.
  2. Name these three types of RNA
  3. Briefly describe the function of each of these types of RNA.

 

Ans: a.  mRNA, tRNA, rRNA.

  1. mRNA moves genetic information from the nucleus to the ribosomes in the cytoplasm. tRNA decodes the genetic message, it matches sequences of three nucleotides to amino acids.  rRNA is involved in the catalysis of amide bond formation.

Level of Difficulty:  Difficult

Section 3.3B

Learning objective: Overview of Nucleic Acid Function

 

 

Chapter 7: Protein Function Part I: Myoglobin and Hemoglobin

 

 

Matching

 

A)  positively cooperative
B)  cyanosis
C)  His E7
D)  decrease
E)  R
F)  hydrogen bonds
G)  increase
H)  symmetry
I)  His F8
J)  ion pairs
K)  T
L)  hemolytic anemia
M  sequencial

 

 

  1. When oxygen binds to heme, the oxygen forms a hydrogen bond with ______.

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. In the ______ state of hemoglobin, the iron ion is out of the plane of the porphyrin ring.

 

Ans:  K

Level of Difficulty:  Easy

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The conversion of hemoglobin from the T to the R state requires breaking of ______ involving C-terminal residues.

 

Ans:  J

Level of Difficulty:  Easy

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Hemoglobin’s subunits bind oxygen in a ______ manner.

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.1.C

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. An increase in pCO2 causes hemoglobin’s affinity for oxygen to ______.

 

Ans:  D

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The absence of 2,3-BPG causes hemoglobin’s affinity for oxygen to______.

 

Ans:  G

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The ______ model of allosterism requires subunits to change conformation simultaneously.

 

Ans:  H

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Sickle cell hemoglobin does not form fibers in the ______ form.

 

Ans:  E

Level of Difficulty:  Easy

Section:  7.1.E

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. When unstable hemoglobin is degraded; degradation products often cause cell lysis, leading to a condition called ______.

 

Ans:  L

Level of Difficulty:  Moderate

Section:  7.1.E

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Mutations that favor the oxidation of the heme iron(II) to iron(III) can cause ______.

 

Ans:  B

Level of Difficulty:  Moderate

Section:  7.1.E

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

Multiple Choice

 

 

  1. Which of the following is not a ligand to the porphyrin ring Fe(II) ion in oxymyoglobin?
  2. A) His E7
  3. B) His F8
  4. C) Nitrogen atoms in the porphyrin ring
  5. D) Oxygen
  6. E) all are ligands

 

Ans:  A

Level of Difficulty:  Moderate

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Which gas does not bind to the porphyrin ring Fe(II) ion in myoglobin?
  2. A) NO
  3. B) CO
  4. C) CO2
  5. D) O2
  6. E) H2S

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Which of the following statements does not apply to the K value in the equation for the oxygen binding curve of myoglobin?
  2. A) It is numerically equal to p50.
  3. B) It is defined as that oxygen partial pressure at which half of the oxygen binding sites are occupied.
  4. C) It is a measure of the affinity of myoglobin for oxygen.
  5. D) If Y > K, then myoglobin is less than 50% saturated with oxygen.
  6. E) It is the value of pO2 at which Y = 0.5.

 

Ans:  D

Level of Difficulty:  Easy

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Myoglobin’s secondary structure is primarily composed of ______________.
  2. A) parallel b-sheets
  3. B) antiparallel b-sheets
  4. C) a-helices
  5. D) W-loops
  6. E) polyproline helices

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Myoglobin’s primary physiological role is to facilitate oxygen ________.
  2. A) storage
  3. B) metabolism
  4. C) binding
  5. D) reduction
  6. E) diffusion

 

Ans:  E

Level of Difficulty:  Easy

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. If the gene for myoglobin is “knocked out” in mice, the mice:
  2. A) have larger lungs.
  3. B) respire extremely rapidly.
  4. C) have dark brown muscle tissue.
  5. D) appear normal, with lighter colored muscle tissue.
  6. E) have their growth stunted.

 

Ans:  D

Level of Difficulty:  Moderate

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Carbon monoxide binds to heme:
  2. A) with a higher affinity than oxygen.
  3. B) resulting in the oxidation of the Fe(II) to Fe(III)
  4. C) in a manner that displaces carbon dioxide, causing CO2
  5. D) from the side opposite oxygen, resulting in a brown colored heme.
  6. E) with a lower affinity than oxygen.

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Myoglobin and a single chain of hemoglobin have similar ______ structures.
  2. A) primary
  3. B) secondary
  4. C) tertiary
  5. D) quaternary
  6. E) none of the above

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The primary structure of mammalian hemoglobin, an a2b2 tetramer, is approximately _____ identical to myoglobin.
  2. A) 2%
  3. B) 18%
  4. C) 50%
  5. D) 78%
  6. E) 98%

 

Ans:  B

Level of Difficulty:  Moderate

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Hemoglobin is a heterotetramer. How many protomers are present in hemoglobin?
  2. A) 0
  3. B) 1
  4. C) 2
  5. D) 3
  6. E) 4

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. What is the type of symmetry that relates the protomers in hemoglobin with respect to each other?
  2. A) C2
  3. B) C4
  4. C) D2
  5. D) D4
  6. E) Tetrahedral symmetry

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Hemerythrin and hemocyanin are:
  2. A) human mutant hemoglobins with decreased oxygen affinity.
  3. B) hemoglobin variants that are found in animals at high altitude.
  4. C) synthetic derivatives of hemoglobin’s heme group used in artificial blood substitutes.
  5. D) oxygen transport proteins found in invertebrates.
  6. E) tetrameric hemoglobin derivatives containing only a-chains (a4 tetramers).

 

Ans:  D

Level of Difficulty:  Easy

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Max Perutz’s investigation of the structure of hemoglobin primarily utilized_____.
  2. A) X-ray crystallography
  3. B) NMR spectroscopy
  4. C) genomics
  5. D) mass spectrometry
  6. E) genetic engineering

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The oxygen binding by hemocyanins is mediated by
  2. A) an iron ion
  3. B) a pair of iron ions
  4. C) a heme group
  5. D) a copper atom
  6. E) a pair of copper atoms

 

Ans:  E

Level of Difficulty:  Difficult

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. When the partial pressure of O2 in venous blood is 30 torr, the saturation of myoglobin with O2 is ______ while the saturation of hemoglobin with O2 is ______.
  2. A) 55, 0.91
  3. B) 91, 0.55
  4. C) 8 torr, 26 torr
  5. D) 91, 0.97
  6. E) none of the above

 

Ans:  B

Level of Difficulty:  Difficult

Section:  7.1.C

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Hemoglobin’s p50 value is about ______ as great as myoglobin’s p50 value.
  2. A) one-tenth
  3. B) half
  4. C) twice
  5. D) ten times
  6. E) twenty times

 

Ans:  D

Level of Difficulty:  Moderate

Section:  7.1.C

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The value of n, the Hill constant (coefficient), for hemoglobin is about ______ as great as the value for myoglobin.
  2. A) half
  3. B) twice
  4. C) three times
  5. D) five times
  6. E) ten times

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.1.C

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Consider a hypothetical hemoglobin-like molecule with a Hill coefficient (constant) of 1 and the same p50 value as normal hemoglobin. Choose the statement below that best describes the two proteins.
  2. A) There is a cooperative interaction between oxygen-binding sites in both the hypothetical and normal hemoglobins.
  3. B) The hypothetical hemoglobin has a greater oxygen affinity than normal hemoglobin.
  4. C) The oxygen binding curve for the hypothetical hemoglobin is hyperbolic, and the curve for normal hemoglobin is sigmoidal.
  5. D) The two hemoglobins would be able to deliver about the same amount of oxygen to the tissues.
  6. E) At pO2 less than p50, normal hemoglobin has a greater YO2

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.1.C

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. The Hill plot shows that the fourth oxygen binds to hemoglobin with a ______-fold greater affinity than the first.
  2. A) 2
  3. B) 5
  4. C) 10
  5. D) 20
  6. E) 100

 

Ans:  E

Level of Difficulty:  Moderate

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. While the binding of O2 to myoglobin as a function of pO2 is described by a simple __________ curve, the binding to hemoglobin is described by a more complex ______ curve.
  2. A) sigmoidal; hyperbolic
  3. B) hyperbolic; sigmoidal
  4. C) exponential; hyperbolic
  5. D) sigmoidal; bell-shaped
  6. E) hyperbolic; concave

 

Ans:  B

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The Bohr effect refers to
  2. A) the decrease in affinity of Hb for O2 when the pH goes down
  3. B) the decrease in affinity of Hb for O2 when the pH goes up
  4. C) the increase in the affinity of Hb for O2 when the O2 concentration goes up
  5. D) the decrease in affinity of Hb for O2 when the BPG concentration goes up
  6. E) the decrease in affinity of Hb for O2 when the BPG concentration goes down

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.1.C

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Which of the following increases the affinity of hemoglobin for O2?
  2. A) an increase in BPG concentration
  3. B) the formation of N-terminal carbamates
  4. C) an increase in pH
  5. D) a decrease in pH
  6. E) an increase in CO2 concentration

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The most rapid way that erythrocytes adapt to high altitudes is
  2. A) by producing genetically altered hemoglobins that have higher O2-binding affinities.
  3. B) by adopting the symmetry model of allosterism.
  4. C) by increasing the concentration of hemoglobin.
  5. D) by relying upon the simpler protein myoglobin.
  6. E) by increasing the intracellular concentration of BPG.

 

Ans:  E

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. The rearrangement of T state hemoglobin to the R state
  2. A) occurs in each protein subunit independently when its heme binds oxygen.
  3. B) requires the binding of at least three oxygen molecules.
  4. C) increases the ion pairing interactions of the C-terminal amino acids.
  5. D) involves the movement of the Fe(II) into the heme plane.
  6. E) opens a central cavity for BPG binding.

 

Ans:  D

Level of Difficulty:  Moderate

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. Which of the following statements about the symmetry model of allosterism is not true?
  2. A) the protein is an oligomer of symmetrically (or pseudosymmetrically) related subunits.
  3. B) the oligomer can exist in two conformational states, which are in equilibrium.
  4. C) the ligand can bind to a subunit in either conformation.
  5. D) the molecular symmetry of the protein is conserved during the conformational change.
  6. E) none of the above.

 

Ans:  E

Level of Difficulty:  Moderate

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. BPG stands for
  2. A)
  3. B)
  4. C)
  5. D)
  6. E)

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Why is the decreased affinity of fetal hemoglobin for BPG advantageous?
  2. A) With fewer BPG molecules bound there are more heme residues available for O2
  3. B) Decreased BPG binding biases the fetal hemoglobin toward the R state.
  4. C) More free BPG is available to bind to adult hemoglobin, resulting in a shift to the R state.
  5. D) BPG is available to bind to fetal myoglobin, helping to release O2 in fetal muscle tissue.
  6. E) none of the above

 

Ans:  B

Level of Difficulty:  Difficult

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. The reaction of carbonic anhydrase catalyzes
  2. A) the formation of carbamates with the concomitant release of protons.
  3. B) the hydration of bicarbonate, resulting in the formation of carbonic acid.
  4. C) the reduction of carbon dioxide with the concomitant consumption of protons.
  5. D) the hydration of carbon dioxide, forming bicarbonate and protons.
  6. E) the hydrolysis of carbamates with the concomitant consumption of protons.

 

Ans:  D

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. During the T to R conformational shift, Fe(II) drags the F-helix via a bond to the side chain of ________.
  2. A) Leu F7
  3. B) Leu F4
  4. C) His F8
  5. D) Leu FG3
  6. E) Val FG5

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.1.D

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Some abnormal hemoglobins have Hill coefficients that are ______ that of normal hemoglobin, indicating that their ability to bind oxygen cooperatively has been compromised.
  2. A) less than
  3. B) greater than
  4. C) much greater than
  5. D) about equal to
  6. E) The correct answer cannot be determined from the information given.

 

Ans:  A

Level of Difficulty:  Moderate

Section:  7.1.E

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. In sickle-cell anemia, the negatively charged glutamic acid residue is replaced by the neutral amino acid ____________.
  2. A) tyrosine
  3. B) lysine
  4. C) valine
  5. D) adenosine
  6. E) glycine

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.1.E

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Hemoglobin S, the variant responsible for the misshapen red blood cells characteristic of the disease sickle-cell anemia, is potentially advantageous to heterozygotes because it confers some level of resistance to the disease _________.
  2. A) rickets
  3. B) AIDS
  4. C) cyanosis
  5. D) polycythemia
  6. E) malaria

 

Ans:  E

Level of Difficulty:  Easy

Section:  7.1.E

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. ______of the world’s human population carries an inherited variant hemoglobin gene.
  2. A) 5%
  3. B) 25%
  4. C) 50%
  5. D) 75%
  6. E) 90%

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.1.E

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin
44.  The repeating functional unit in a myofibril is called

  1. A) the A band.
  2. B) the I band.
  3. C) the sarcomere.
  4. D) the H zone.
  5. E) the M disk.

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.2.A

Learning objective: Muscle Contraction

 

 

  1. Muscle contraction is directly caused by
  2. A) structural changes in actin.
  3. B) structural changes in myosin.
  4. C) structural changes in the A band.
  5. D) structural changes in the Z disk.
  6. E) None of the above is correct.

 

Ans:  E

Level of Difficulty:  Moderate

Section:  7.2.A

Learning objective: Muscle Contraction

 

 

  1. Muscle contraction is directly caused by
  2. A) structural changes in actin.
  3. B) structural changes in myosin.
  4. C) thick and thin filaments sliding past each other.
  5. D) structural changes in the Z disk.
  6. E) None of the above is correct.

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.2.A

Learning objective: Muscle Contraction

  1. Which of the statements about muscle contraction is correct?
  2. A) During muscle contraction the sarcomere becomes shorter.
  3. B) During muscle contraction the I band becomes shorter.
  4. C) During muscle contraction the H zone becomes shorter.
  5. D) During muscle contraction the distance between the Z disk and the M disk becomes shorter.
  6. E) All of the answers above are correct.

 

Ans:  E

Level of Difficulty:  Moderate

Section:  7.2.A

Learning objective: Muscle Contraction

 

 

  1. Which of the statements about muscle contraction is not true?
  2. A) During muscle contraction the sarcomere becomes shorter.
  3. B) During muscle contraction the I band becomes shorter.
  4. C) During muscle contraction the H zone becomes shorter.
  5. D) During muscle contraction the A band becomes shorter
  6. E) During muscle contraction the distance between the Z disk and the M disk becomes shorter.

 

Ans:  D

Level of Difficulty:  Moderate

Section:  7.2.A

Learning objective: Muscle Contraction

 

 

  1. What are the main bonds or forces that stabilize the dimer formed by two myosin heavy chains?
  2. A) hydrophobic interactions
  3. B) hydrogen-bonds
  4. C) ionic interactions
  5. D) disulfide bonds
  6. E) isopeptide bonds

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.2.A

Learning objective: Muscle Contraction

  1. During muscle contraction
  2. A) myosin pulls actin filaments toward the M disk.
  3. B) myosin pushes actin filaments toward the Z disk.
  4. C) actin pulls myosin toward the Z disk.
  5. D) actin pushes myosin toward the M disk.
  6. E) All of the answers above are correct.

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.2.A

Learning objective: Muscle Contraction

 

 

  1. Which statement about myosin is not true?
  2. A) Myosin is a heterohexamer.
  3. B) Myosin contains two globular heads.
  4. C) Myosin contains six different polypeptides
  5. D) Myosin aggregates to form thick filaments
  6. E) All of the answers above are true of myosin.

 

Ans:  E

Level of Difficulty:  Easy

Section:  7.2.A

Learning objective: Muscle Contraction

 

 

  1. Which statement about actin is not true?
  2. There are two actin genes, one for F-actin and one for G-actin.
  3. Monomeric G-actin polymerizes to form F-actin.
  4. Actin filaments are polar (the ends can be distinguished).
  5. Actin can bind ATP.
  6. Actin is a common protein in nonmuscle cells.

 

Ans:  A

Level of Difficulty:  Moderate

Section:  7.2.A

Learning objective: Muscle Contraction

  1. The energy needed to drive muscle contraction comes from ATP hydrolysis that is carried out by
  2. A) G-actin.
  3. B) F-actin.
  4. C) myosin heads.
  5. D) myosin tails.
  6. E)

 

Ans:  C

Level of Difficulty:  Easy

Section:  7.2.B

Learning objective: Muscle Contraction

 

 

  1. During muscle contraction myosin heads
  2. A) walk along thick filaments toward the M disk.
  3. B) walk along thick filaments toward the Z disk.
  4. C) walk along thin filaments toward the M disk.
  5. D) walk along the thin filaments toward the H zone.
  6. E) walk along the thin filaments toward the Z disk.

 

Ans:  E

Level of Difficulty:  Moderate

Section:  7.2.B

Learning objective: Muscle Contraction

 

  1. Muscle contraction is triggered
  2. A) in response to an increase in the cytoplasmic Ca2+
  3. B) in response to a decrease in the cytoplasmic Ca2+
  4. C) in response to an increase in the cytoplasmic cAMP concentration.
  5. D) in response to a decrease in the cytoplasmic cAMP concentration.
  6. E) in response to an increase in the cytoplasmic titin concentration.

 

Ans:  A

Level of Difficulty:  Moderate

Section:  7.2.B

Learning objective: Muscle Contraction

  1. Which statement about actin is correct?
  2. A) Actin is expressed only in muscle.
  3. B) Actin is expressed at low levels in most cells.
  4. C) No known function has been described for actin in nonmuscle cells.
  5. D) Nonmuscle cells only contain G actin.
  6. E) Actin is the most abundant cytoplasmic protein in many cell types.

 

Ans:  E

Level of Difficulty:  Moderate

Section:  7.2.C

Learning objective: Muscle Contraction

 

  1. Which of the following statements about actin is not true?
  2. A) Actin is the most abundant cytoplasmic protein in many cell types.
  3. B) Actin forms microfilaments in many cell types.
  4. C) Actin plays an important role in endocytosis.
  5. D) Actin is present only as monomers in nonmuscle cells.
  6. E) Actin filaments are dynamic, they grow at one end and they lose subunits at the other end.

 

Ans:  D

Level of Difficulty:  Moderate

Section:  7.2.C

Learning objective: Muscle Contraction

 

  1. Treadmilling refers to
  2. A) myosin heads walking along actin microfilaments.
  3. B) actin and myosin filaments sliding along each other.
  4. C) actin monomers moving through a microfilament from the + end to the – end.
  5. D) synthesis and degradation of actin monomers.
  6. E) the interactions between actin and tropomyosin.

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.2.C

Learning objective: Muscle Contraction

  1. Humoral immunity refers to that part of the immune response that is mediated by
  2. A) T lymphocytes.
  3. B)
  4. C)
  5. D) the thymus.
  6. E) the skin.

 

Ans:  B

Level of Difficulty:  Easy

Section:  7.3.A

Learning objective: Antibodies

 

 

  1. Humoral immunity is mediated by soluble molecules. Which cell type produces the soluble molecules that carry out the humoral immunity?
  2. A) T cells
  3. B) B cells
  4. C) macrophages
  5. D) neutrophils
  6. E) monocytes

 

Ans:  B

Level of Difficulty:  Easy

Section:  7.3.A

Learning objective: Antibodies

 

 

  1. How many different classes of antibodies are produced by the human immune system?
  2. A) 1
  3. B) 2
  4. C) 3
  5. D) 4
  6. E) 5

 

Ans:  E

Level of Difficulty:  Easy

Section:  7.3.A

Learning objective: Antibodies

  1. IgG is the most common immunoglobulin in the circulatory system and in the extravascular fluid. It is composed of two light chains and two heavy chains.  What is the approximate molecular mass of an IgG molecule?
  2. A) 23 kDa
  3. B) 75 kDa
  4. C) 150 kDa
  5. D) 360 kDa
  6. E) 950 kDa

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.3.A

Learning objective: Antibodies

 

  1. IgG is one of five classes of antibodies that can be produced by our immune system. IgGs have a molecular mass of approximately 150 kDa, what is their subunit composition?
  2. A) 2 light chains and 2 heavy chains
  3. B) 2 light chains, 2 heavy chains, and a J chain
  4. C) 4 light chains, 4 heavy chains, and a J chain
  5. D) 6 light chains, 6 heavy chains, and a J chain
  6. E) 10 light chains, 10 heavy chains , and a J chain.

 

Ans:  A

Level of Difficulty:  Easy

Section:  7.3.A

Learning objective: Antibodies

 

 

  1. Which class of antibodies has been implicated in allergic reactions?

 

  1. A) IgA
  2. B) IgD
  3. C) IgE
  4. D) IgG
  5. E) IgM

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.3.A

Learning objective: Antibodies

  1. How many antigen-binding sites are present on an IgG molecule?
  2. A) 1
  3. B) 2
  4. C) 3
  5. D) 4
  6. E) 5

 

Ans:  B

Level of Difficulty:  Easy

Section:  7.3.A

Learning objective: Antibodies

 

 

  1. How many antigen-binding sites are present on an IgM molecule?
  2. A) 2
  3. B) 4
  4. C) 10
  5. D) 16
  6. E) 25

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.3.A

Learning objective: Antibodies

 

 

  1. Fab fragments can be generated by
  2. A) reduction of IgG molecules.
  3. B) oxidation of IgG molecules.
  4. C) limited digestion of IgG molecules with papain.
  5. D) combining two light chains.
  6. E) combining two heavy chains.

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.3.A

Learning objective: Antibodies

  1. Which statement about antigen-binding sites in antibodies is false?
  2. A) An antigen-binding site on an IgG is formed by the amino-terminal ~110 amino acids of a light chain and the amino terminal ~110 amino acids of a heavy chain.
  3. B) An antigen-binding site on an IgG is formed by the variable region of a light chain and the variable region of a heavy chain.
  4. C) The antigen-binding site is composed of two Ig folds.
  5. D) Antigen-binding specificity is determined by the sequences of the hypervariable sequences in both the light chain and the heavy chain.
  6. E) Antigen binding specificity is determined exclusively by the sequences in the carboxy-terminal ~110 amino acids in the light chain and the heavy chain.

 

Ans:  E

Level of Difficulty:  Moderate

Section:  7.3.B

Learning objective: Antibodies

 

 

  1. The Ig fold can be described as a
  2. A) globular fold composed of a
  3. B) a globular fold composed of a four helix bundle.
  4. C) a globular fold composed of a b
  5. D) a globular fold composed of b
  6. E) a coiled-coil.

 

Ans:  C

Level of Difficulty:  Moderate

Section:  7.3.B

Learning objective: Antibodies

SHORT ANSWER

 

 

  1. Myoglobin is an oxygen binding protein in muscle. Describe in one sentence the overall structure of myoglobin.

 

Ans:  Myoglobin is a globular protein composed of 8 a helices that forms a hydrophobic pocket that contains the heme group.

Level of Difficulty:  Moderate

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. What is the primary physiological function of myoglobin in most mammals?

 

Ans:  The primary physiological function of myoglobin in most mammals is to increase the solubility for O2 in muscle tissue and thereby increasing the diffusion rate.

Level of Difficulty:  Moderate

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. It appears that the heme group in myoglobin binds the O2. What is the function of the polypeptide?

 

Ans:  The polypeptide performs various functions:  1.  The polypeptide provides solubility for the heme group, which is very non-polar.  2. The polypeptide prevents permanent oxidation of the Fe(II).  3.  The polypeptide helps coordinate the Fe(II) (His F8)  4.  The polypeptide forms a H-bond with the O2 (His E7).

Level of Difficulty:  Difficult

Section:  7.1.A

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

 

  1. Mammals and other animals have a circulatory system because diffusion is to slow to supply the tissues with oxygen in animals that are larger than 2 millimeter. Explain in one sentence why these circulatory systems contain hemoglobin or other oxygen binding proteins?

 

Ans:  Oxygen-binding proteins increase the solubility of oxygen in the fluid of the circulatory system.  This is important because oxygen is not very soluble in aqueous solutions.

Level of Difficulty:  Difficult

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. The graph below shows the O2-binding curves for myoglobin (Mb) and hemoglobin (Hb).
  2. Label the two curves (indicate which one represents Mb and which one represents Hb).

 

 

  1. Use the graph to determine the Kd of myoglobin for O2 (show your approach).
  2. What is the difference between myoglobin and hemoglobin that cause the O2-binding curves to so be different?
  3. Why is it important that hemoglobin has these particular O2-binding characteristics?

 

Ans:  a.  See graph.

  1. Kd equals 3-4 torr (see graph).
  2. Mb has one subunit, Hb has 4 subunits. The sigmoid binding curve is a consequence of positive cooperativity between the 4 O2-binding sites in Hb.  The hyperbolic binding curve for myoglobin is the result of oxygen binding reaction being noncooperative.
  3. As a consequence of positive cooperation Hb has a high affinity for O2 when the O2 concentration is high (in the lungs) and low affinity for O2 when the O2 concentration is low (in the tissues). As a consequence Hb binds large amount of O2 in the lungs and releases large amounts of O2 in the tissues, resulting in efficient transport of O2.

Level of Difficulty:  Difficult

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

  1. You have been studying O2 binding to a hemerythrin-like protein isolated from an exotic marine worm. Your O2-binding data are shown in the table below.
  2. Use the data to generate an O2-binding curve (do not forget to mark the axes).
  3. Use the curve to estimate the Kd for the interaction.
  4. Is there any evidence from your data that this hemoglobin-like protein binds O2 in a cooperative manner (briefly explain your answer)?

 

 

[Ligand] in µM Y
21 0.11
42 0.28
79 0.37
118 0.42
257 0.58
362 0.66
535 0.78
745 0.86
900 0.89
1052 0.92

 

 

 

 

 

Ans:  a.  see curve

  1. see curve, Kd equals 180 µM
  2. there is no evidence for cooperative binding of O2 to this protein, because the binding curve is hyperbolic and not sigmoid.

Level of Difficulty:  Difficult

Section:  7.1.B

Learning objective: Oxygen Binding to Myoglobin and Hemoglobin

 

Chapter 17: Citric Acid Cycle

Matching

Choose the correct answer from the list. Not all the answers will be used.

A) oxaloacetate
B) malate synthase
C) malate
D) malonate
E) Krebs
F) aconitase
G) succinyl-CoA synthetase
H) a-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase

 

 

  1. The citric acid cycle is also called the ______ cycle.
    Ans: E
    Level of Difficulty: Easy
    Section:  1
    Learning Objective:  Overview of the Citric Acid Cycle
  2. ______ is the first compound that is oxidized in the citric acid cycle.
    Ans: K
    Section: 3.C
    Level of Difficulty:  Moderate
    Learning Objective:  Enzymes of the Citric Acid Cycle
  3. ______ catalyzes a substrate-level phosphorylation reaction within the citric acid cycle.
    Ans: G
    Section:  3.E
    Level of Difficulty:  Moderate
    Learning Objective:  Enzymes of the Citric Acid Cycle
  4. ______ is used in the first reaction of the citric acid cycle and regenerated upon completion of one turn of the citric acid cycle.
    Ans: A
    Section: 1
    Level of Difficulty:  Easy
    Learning Objective: Overview of the Citric Acid Cycle
  5. A membrane-bound enzyme of the citric acid cycle that catalyzes an oxidation reaction is ______.
    Ans: L
    Section: 3.F
    Level of Difficulty:  Easy
    Learning Objective:  Enzymes of the Citric Acid Cycle
  6. The name of a citric acid cycle intermediate that is derived from the Latin word for “apple” is ______.
    Ans: C
    Section: 1
    Level of Difficulty:  Easy
    Learning Objective:  Overview of the Citric Acid Cycle
  7. The enzyme ______ is unique because it contains an iron-sulfur cluster but does not participate in a redox reaction.
    Ans: F
    Section: 3.B
    Level of Difficulty:  Moderate
    Learning Objective:  Enzymes of the Citric Acid Cycle
  8. The compound ______ is a structural analog and competitive inhibitor of the enzyme succinate dehydrogenase.
    Ans: D
    Section: 3.F
    Level of Difficulty:  Moderate
    Learning Objective:  Enzymes of the Citric Acid Cycle
  9. The enzyme ______ is part of the glyoxylate cycle that occurs in plants, bacteria, and fungi.
    Ans: B
    Section: 5.C
    Level of Difficulty:  Moderate
    Learning Objective:  Reactions Related to the Citric Acid Cycle
  10. _____ and pyruvate can be combined in an ATP dependent reaction that regenerates one of the key intermediates in the citric acid cycle.

Ans: I
Section:  17.5.B
Level of Difficulty:  Moderate
Learning Objective:  Reactions Related to the Citric Acid Cycle

 

 

 

Multiple Choice

  1. Which of the following coenzymes is required by E1 of the pyruvate dehydrogenase complex for catalytic activity?
    1. thiamine pyrophosphate
    2. lipoamide
    3. coenzyme A
    4. NAD+
    5. FAD

Answer: A
Section:  17.2.B
Level of Difficulty:  Easy
Learning Objective:  Synthesis of Acetyl-Coenzyme A

 

  1. E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached via an amide linkage to a ______ residue on the enzyme?
    1. tyrosine
    2. serine
    3. lysine
    4. arginine
    5. cysteine

Answer:  C
Section:  17.2.B
Level of Difficulty:  Easy
Learning Objective:  Synthesis of Acetyl-Coenzyme A

 

  1. Which of the following is an intermediate between citrate and isocitrate in the citric acid cycle?
    1. succinyl-CoA
    2. citryl-CoA
    3. oxalosuccinate
    4. succinyl-phosphate
    5. cis-aconitate

Answer: E
Section:  17.3.B
Level of Difficulty:  Easy
Learning Objective: Enzymes of the Citric Acid Cycle

 

 

 

 

 

 

 

 

  1. Condensation of ____ with oxaloacetate yield citrate.
    1. acetyl-CoA
    2. α-ketoglutarate
    3. isocitrate
    4. citrophosphate
    5. oxalosuccinate

Answer: A
Section:  17.3.A
Level of Difficulty:  Easy
Learning Objective:  Enzymes of the Citric Acid Cycle

 

  1. During the oxidation of isocitrate, _____ is decarboxylated to form a-ketoglutarate.
    1. hydroxyethyl-TPP
    2. carboxybiotin
    3. oxalosuccinate
    4. succinyl-phosphate
    5. none of the above

Answer: C
Section:  17.3.C
Level of Difficulty:  Moderate
Learning Objective:  Enzymes of the Citric Acid Cycle

 

  1. The reaction catalyzed by _____ requires an enzyme bound flavin coenzyme.
    1. isocitrate dehydrogenase
    2. a-ketoglutarate dehydrogenase
    3. succinyl-CoA synthetase
    4. succinate dehydrogenase
    5. malate dehydrogenase

Answer: D
Section:  17.3.F
Level of Difficulty:  Easy
Learning Objective:  Enzymes of the Citric Acid Cycle

 

  1. In eukaryotes, the citric acid cycle occurs in the _____ and therefore requires that reactants of the citric acid cycle be transported from the _____.
    1. cytosol; mitochondrial matrix
    2. mitochondrial matrix; cytosol
    3. endoplasmic reticulum; mitochondrial matrix
    4. inner mitochondrial membrane; mitochondrial matrix
    5. outer mitochondrial membrane; cytosol

Answer: B
Section:  17.1
Level of Difficulty:  Moderate
Learning Objective: Overview of the Citric Acid Cycle

  1. How many NADH are produced when one acetyl group is oxidized in the citric acid cycle?
    1. 1
    2. 2
    3. 3
    4. 4
    5. more than 4

Answer:  C
Section:  17.1
Level of Difficulty:  Easy
Learning Objective:  Overview of the Citric Acid Cycle

 

  1. Which of the following utilizes intermediates of the citric acid cycle?
  2. gluconeogenesis
  3. amino acid biosynthesis

III.  fatty acid oxidation

  1. glycolysis
    1. I only
    2. II only
    3. I, II, III
    4. I, II
    5. I, IV

Answer: D
Section:  17.5
Level of Difficulty:  Moderate
Learning Objective: Reactions Related to the Citric Acid Cycle

 

  1. The reaction catalyzed by pyruvate carboxylase is an example of a(n) ______ reaction because it replenishes the citric acid cycle intermediates that have been siphoned off for use in other reactions.
    1. amphibolic
    2. amphipathic
    3. anaplerotic
    4. cataplerotic
    5. none of the above

Answer:  C
Section:  17.5.B
Level of Difficulty:  Easy
Learning Objective: Reactions Related to the Citric Acid Cycle

 

 

 

 

 

  1. Which of the following is oxidized by a multienzyme complex that requires five different coenzymes?
    1. A and B
    2. A, B, and C

Answer:  C

Section:  17.2.A

Level of Difficulty:  Moderate

Learning Objective:  Synthesis of Acetyl-Coenzyme A

 

  1. The isomerization of citrate to isocitrate
    1. is the reaction of the citric acid cycle that occurs spontaneously without enzymatic catalysis.
    2. protects cells from the toxic effects of arsenite ion.
    3. converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized.
    4. is one major regulatory step for the citric acid cycle because it functions as a rate limiting step.
    5. A and B

Answer:  C

Section:  17.3.B

Level of Difficulty:  Difficult

Learning Objective:  Enzymes of the Citric Acid Cycle

 

 

 

 

 

 

 

 

 

 

 

 

  1. Which of the following is(are) TRUE concerning the metabolic reaction shown below?

Pyruvate  +  NAD+  +  CoA-SH    Acetyl-CoA  +  NADH  + H+   +  CO2

  1. The enzyme that catalyzes this reaction contains a pyridoxal phosphate prosthetic group.
  2. This reaction is an oxidative decarboxylation.

III.  The enzyme that catalyzes this metabolic conversion is activated by high concentrations of ATP.

  1. I, II, III
  2. II, III
  3. II only
  4. III only
  5. I, II

Answer:  C

Section: 17.2.B

Level of Difficulty:  Difficult

Learning Objective: Synthesis of Acetyl-Coenzyme A

 

  1. Which of the following causes pyruvate dehydrogenase kinase to catalyze the phosphorylation and inactivation of E1 in the pyruvate dehydrogenase complex?
    1. elevated concentrations of NADH and ATP
    2. elevated concentrations of NAD+ and ADP
    3. insulin
    4. elevated concentrations of acetyl-CoA
    5. C and D

Answer: A

Section: 17.4.A

Level of Difficulty: Difficult

Learning Objective: Regulation of the Citric Acid Cycle

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. If acetyl-CoA labeled with 14C, as shown in the figure to the right, were used as the substrate for the citric acid cycle, which of the following intermediates would be produced during the first round of the cycle?

Answer: B

Section: 17.1

Level of Difficulty:  Difficult

Learning Objective: Overview of the Citric Acid Cycle

 

 

  1. Which of the following uses inherent length and flexibility to facilitate transfer of an acetyl group?
    1. FAD
    2. NAD+
    3. lipoamide
    4. thiamine pyrophosphate
    5. coenzyme A

Answer: C

Section: 17.2.B

Level of Difficulty: Moderate

Learning Objective: Synthesis of Acetyl-Coenzyme A

 

  1. Which of the following structures represents a molecule that is added to succinate to form CoA and malate?

Answer: E

Section: 17.5.C

Level of Difficulty:  Difficult

Learning Objective: Reactions Related to the Citric Acid Cycle

 

  1. Which of the following best describes the importance of the citric acid cycle as a central pathway of metabolism?
    1. It allows recovery of energy from carbohydrates only.
    2. It allows recovery of energy from fatty acids only.
    3. It allows recovery of energy from amino acids only.
    4. It allows recovery of energy from several metabolic fuels that are broken down to acetyl-CoA.
    5. A and B

Answer: D

Section:  17.1

Level of Difficulty:  Easy
Learning Objective: Overview of the Citric Acid Cycle

 

 

 

 

 

 

 

 

 

 

  1. Which of the following coenzymes is required by the pyruvate dehydrogenase complex for reoxidation of E3?
    1. thiamine pyrophosphate
    2. pyridoxal phosphate
    3. coenzyme A
    4. FAD
    5. NAD+

Answer: E

Section:  17.2.B

Level of Difficulty:  Difficult
Learning Objective: Synthesis of Acetyl-Coenzyme A

 

  1. Which of the following enzymes catalyzes a reaction with the pictured compound as an intermediate?
    1. a-ketoglutarate dehydrogenase
    2. succinyl-CoA synthetase
    3. succinate dehydrogenase
    4. fumarase
    5. malate dehydrogenase

Answer: B

Section:  17.3.E

Level of Difficulty:  Moderate
Learning Objective: Enzymes of the Citric Acid Cycle

 

  1. Which of the following can be said about the isocitrate product of aconitase?
    1. The product always has the R
    2. The product always has the S
    3. The product is not chiral.
    4. The product can exist in either the R or S configuration in eukaryotes.
    5. If the product is in the R configuration it has by passed the cis-aconitate intermediate.

Answer: A

Section:  17.3.B

Level of Difficulty:  Moderate
Learning Objective: Enzymes of the Citric Acid Cycle

 

 

 

 

 

 

 

 

 

 

  1. Which of the following enzymes of the citric acid cycle is inhibited by ATP?
    1. citrate synthase
    2. isocitrate dehydrogenase
    3. a-ketoglutarate dehydrogenase
    4. succinyl-CoA synthetase
    5. A and B

Answer: B

Section:  17.4.B

Level of Difficulty:  Moderate
Learning Objective: Regulation of the Citric Acid Cycle

 

  1. Which of the following organisms does not utilize the glyxolate cycle?
    1. trees
    2. bacteria
    3. fungi
    4. mammals
    5. All of the above utilize the glyxolate cycle when necessary.

Answer: D

Section:  17.5.C

Level of Difficulty:  Easy
Learning Objective: Reactions Related to the Citric Acid Cycle

 

  1. The figure at right represents an intermediate in the reaction catalyzed by which of the following enzymes?
    1. enolase
    2. aldolase
    3. pyruvate decarboxylase
    4. glyceraldehyde-3-phosphate dehydrogenase
    5. lactate dehydrogenase

Answer: C

Section:  17.2.B

Level of Difficulty:  Moderate
Learning Objective: Synthesis of Acetyl-Coenzyme A

 

 

 

 

 

 

 

 

 

 

  1. Which of the following amino acid residues facilitates the transfer of a phosphate group in the reaction producing succinate and GTP?
    1. aspartate
    2. glutamate
    3. histidine
    4. lysine
    5. serine

Answer: C

Section:  17.3.E

Level of Difficulty:  Difficult
Learning Objective: Enzymes of the Citric Acid Cycle

 

  1. Which of the following citric acid cycle intermediates can be converted to aspartate via transamination?
    1. citrate
    2. a-ketoglutarate
    3. succinate
    4. fumarate
    5. oxaloacetate

Answer: E

Section:  17.5.A

Level of Difficulty:  Moderate
Learning Objective: Reactions Related to the Citric Acid Cycle

 

  1. Considering the reactions within the citric acid cycle, which of the following molecules will be produced from the intermediate pictured on the right?
    1. citrate
    2. isocitriate
    3. succinate
    4. succinyl-CoA
    5. α-ketoglutarate

Answer: B

Section:  17.3.B

Level of Difficulty:  Moderate
Learning Objective: Enzymes of the Citric Acid Cycle

 

 

 

 

 

 

 

 

 

  1. Consider the following reaction which has a ∆G˚’ ≈ +30 kJ/mol.

malate  +  NAD+  →  oxaloacetate +  NADH + H+

In muscle cells, the reaction proceeds as written.  Which of the following explains how the reaction occurs as written despite the positive value for DG°’?

  1. It is thermodynamically favored under standard conditions.
  2. In the cell, it is kinetically favored, even though it’s thermodynamically unfavorable.
  3. The concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell.
  4. [H+] must be higher in muscle than under standard conditions, thus altering ∆G˚ to ∆G˚’.
  5. None of the above

Answer: C

Section: 17.5

Level of Difficulty:  Difficult

Learning Objective: Reactions Related to the Citric Acid Cycle

 

  1. Germinating plant seeds can convert acetyl-CoA (obtained from fatty acids stored as oils) into carbohydrates, whereas animals are incapable of converting fatty acids into glucose. This difference is due to the fact that:
    1. animals have glycogen and don’t need to make glucose from fatty acids.
    2. plants use the glyoxylate cycle to convert two acetyl CoA to oxaloacetate, a precursor for gluconeogenesis.
    3. plant seeds use photosynthesis to make sugar.
    4. animals use the citric acid cycle selectively for energy production, whereas plants primarily use glycolysis.
    5. B and D

Answer:  B

Section: 17.5.C

Level of Difficulty:  Moderate

Learning Objective: Reactions Related to the Citric Acid Cycle

 

  1. How many electrons are transferred from one acetyl group during the citric acid cycle?
    1. 2
    2. 4
    3. 6
    4. 8
    5. 10

Answer:  D

Section: 17.4

Level of Difficulty:  Easy

Learning Objective: Regulation of the Citric Acid Cycle

 

  1. An individual with a shortage of B vitamins (which include thiamine and riboflavin) may feel fatigued as a result of decreased pyruvate dehydrogenase activity. Which of the following would be TRUE regarding this shortage?
    1. The amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased.
    2. A decrease in the amount of NADH would likely decrease activity of citrate synthase.
    3. Flux through the citric acid cycle would cease until adequate pyruvate is available.
    4. none of the above
    5. all of the above

Answer:  A

Section: 17.4

Level of Difficulty:  Difficult

Learning Objective: Regulation of the Citric Acid Cycle

 

  1. Which of the following would decrease activity of the citric acid cycle overall?
  2. high concentration of NADH
  3. high concentration of Ca2+

III.  high concentration of ATP

  1. high concentration of citrate

 

  1. I only
  2. I, II, III, IV
  3. I, III
  4. I, III, IV
  5. I, IV

 

Answer:  D

Section: 17.4

Level of Difficulty:  Difficult

Learning Objective: Regulation of the Citric Acid Cycle

 

  1. Which of the following steps of the citric acid cycle conserves the energy of a high energy thioester bond?
    1. the reaction catalyzed by succinate dehydrogenase.
    2. the reaction that produces oxalacetate.
    3. the condensation reaction that produces citrate.
    4. the reaction catalyzed by α-ketoglutarate dehydrogenase.
    5. the conversion of citrate to isocitrate.

Answer:  D

Section: 17.3.E

Level of Difficulty:  Moderate

Learning Objective: Enzymes of the citric acid cycle

 

 

  1. Which of the following enzymatic reactions is favorable both under physiological conditions and under standard conditions?
    1. The reaction catalyzed by isocitrate dehydrogenase.
    2. The reaction catalyzed by malate dehydrogenase.
    3. The reaction catalyzed by succinate dehydrogenase.
    4. all of the above
    5. none of the above

Answer:  A

Section: 17.4

Level of Difficulty:  Moderate

Learning Objective: Regulation of the citric acid cycle

 

  1. One turn of the citric acid cycle generates
    1. 2 FADH2, 3 ATP, 1 NADH
    2. 1 NAD+, 2FADH2, 1 ATP
    3. 1 GTP, 3 NADH, 1 FADH2
    4. 1 FAD, 2 ATP, 3 NADH
    5. 1 FADH2, 1GTP, 2 NADH

Answer:  C

Section: 17.1

Level of Difficulty:  Moderate

Learning Objective: Overview of the citric acid cycle

 

  1. Which reaction below produces GTP in the citric acid cycle?
    1. isocitrate à a-ketoglutarate
    2. a-ketoglutarate à succinyl CoA
    3. succinyl CoA à succinate
    4. fumarate à malate
    5. malate à oxaloacetate

Answer:  C

Section: 17.1

Level of Difficulty:  Moderate

Learning Objective: Overview of the citric acid cycle

 

 

 

 

 

 

 

 

 

 

 

 

  1. Which of the following statements correctly and most accurately describes the function of FAD in the pyruvate dehydrogenase enzyme complex?

 

  1. NADH passes electrons to FAD to form FADH2.
  2. Lipoamide passes electrons through FADH2, which almost instantly passes them to NAD thus forming NADH.
  3. FADH2 donates electrons to lipoamide thus regenerating FAD.
  4. Lipoamide oxidizes NADH to NAD by passing electrons to FAD.
  5. NAD accepts electrons directly from lipoamide, which has gained them via oxidation of FADH2.

Answer:  B

Section: 17.2.B

Level of Difficulty:  Difficult

Learning Objective: Synthesis of Acetyl-Coenzyme A

 

  1. Which of the following is TRUE regarding the discovery of the citric acid cycle?

 

  1. One of the first discoveries was the involvement of coenzyme A in the                                                           production of GTP.
  2. Krebs had knowledge of the sequence of reactions before he was able to                                                                   demonstrate the link of the cycle to glucose metabolism.

III.  The citric acid cycle was the first cyclic pathway discovered.

  1. Krebs demonstrated the involvement of the citric acid cycle in oxidation of                                                  amino acid and fatty acids.

 

  1. I, II, III, IV
  2. I, II, III
  3. II, III
  4. III, IV
  5. II, IV

 

Answer:  B

Section: 17.1, Box 17-1

Level of Difficulty:  Moderate

Learning Objective: Overview of the citric acid cycle, Box 17-1

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. Which of the following represents a point of regulation for the citric acid cycle?
  2. pyruvate dehydrogenase complex
    II.  aconitase

III.  isocitrate dehydrogenase

  1. fumarase

 

  1. I, II, III, IV
  2. I, II, IV
  3. II, III
  4. I, III
  5. I, IV

Answer:  D

Section: 17.4

Level of Difficulty:  Moderate

Learning Objective: Regulation of the citric acid cycle

 

  1. Bioinformatics has identified some enzymes used in the citric acid cycle in primitive bacteria. Once such a cycle utilized many of the citric acid cycle intermediates but occurred in the reverse direction.  Researchers suspect which of the following based on this information?

 

  1. Researchers suspect that the “original” citric acid cycle was used by all species.
  2. Researchers suspect that portions of the reverse cycle may have been responsible for fixing CO2
  3. Researchers suspect that early methods for converting pyruvate to acetyl CoA did not exist.
  4. Researchers suspect that the current “clockwise” version of the citric acid cycle could be used to help humans feed off CO2.
  5. Researchers suspect that primitive prokaryotic use of the citric acid enzymes were focused on the production of CO2 rather than the use of CO2.

 

 

Answer:  B

Section:  Box 17-3

Level of Difficulty:  Difficult

Learning Objective: Box 17-3