Biochemistry, 6th Edition Reginald Garrett – Test Bank

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1. A gene can be defined as:

  a. the unique function that some cells have but other cells do not have.
  b. a specific segment of nucleotide bases in DNA that encode for the synthesis of a particular protein.
  c. a single strand of DNA that is designated as the sense strand.
  d. a functional segment of a unique protein.
  e. the segment of DNA that is changed in a mutation.

 

ANSWER:   b

 

2. Proteins with two different polypeptide chains are:

  a. monomeric proteins.
  b. trimeric proteins.
  c. homodimeric proteins.
  d. heterodimeric proteins.
  e. none of the above.

 

ANSWER:   d

 

3. Hemoglobin is an α2, β2 ____ whereas, glutamine synthetase from E. coli is an α12 ____.

  a. -homodimer, -homomultimer
  b. -heteromultimer, -homomultimer
  c. -homomultimer, -heterodimer
  d. -heterodimer, -monomeric protein
  e. -heterodimer, -homomultimer

 

ANSWER:   b

 

4. Fibrous proteins, such as collagen, have which one of the following properties?

  a. Highly soluble in water.
  b. Their hydrophilic residues are directed into the interior of the protein.
  c. Exhibit enzymatic activity.
  d. Serve structural roles in the cell.
  e. Monomeric.

 

ANSWER:   d

 

5. Which of the following IS NOT a characteristic of globular proteins?

  a. Insoluble in water.
  b. Roughly spherical.
  c. Folded so that the hydrophobic amino acids are in the interior of the molecule.
  d. Hydrophobic side chains are exposed to the water.
  e. None, all are true.

 

ANSWER:   a

 

6. Molecules of a given protein have all EXCEPT:

  a. a fixed amino acid composition.
  b. a defined amino acid sequence.
  c. a sequence read from C-terminal end to N-terminal end.
  d. an invariant molecular weight.
  e. a nucleotide sequence from which they are encoded.

 

ANSWER:   c

 

7. Membrane proteins differ from globular proteins in that:

  a. membrane associated amino acids usually have polar side chains.
  b. membrane proteins are much more soluble in detergents than water.
  c. membrane proteins usually have more hydrophobic amino acids.
  d. globular proteins are water insoluble.
  e. All are true.

 

ANSWER:   b

 

8. A common reaction of two cysteine residues in proteins results in the formation of ____.

  a. thioester bonds
  b. disulfide bonds
  c. dithiol bonds
  d. thioether bonds
  e. none of the above

 

ANSWER:   b

 

9. The amino acid sequence is defined as ____ structure.

  a. primary
  b. secondary
  c. tertiary
  d. quaternary
  e. all are true

 

ANSWER:   a

 

10. α-Helix and β-strand are components of ____ structure

  a. primary
  b. secondary
  c. tertiary
  d. quaternary
  e. all are true

 

ANSWER:   b

 

11. All of the information necessary for a protein to achieve its intricate architecture is contained within its ____ structure.

  a. primary
  b. secondary
  c. tertiary
  d. quaternary
  e. all are true

 

ANSWER:   a

 

12. The formation of a disulfide bond would be an example of what level of protein structure?

  a. primary
  b. secondary
  c. tertiary
  d. quaternary
  e. both c and d are correct

 

ANSWER:   e

 

13. Which of the following IS NOT a characteristic of a protein’s overall conformation?

  a. The overall three-dimensional architecture of the protein.
  b. Achieved by breaking and reforming covalent bonds.
  c. Achieved by rotations about each single bond along the peptide backbone.
  d. The result of amino acid side-chain interactions.
  e. None, all are true.

 

ANSWER:   b

 

14. Which of the following levels of protein structure is correctly defined?

  a. primary: interaction between subunits of a protein
  b. secondary: hydrogen bond arrangement of polar R-groups
  c. tertiary: three dimensional arrangement of all atoms in a single peptide
  d. quaternary: order of amino acid residues in the peptide chain
  e. none of the above are correct

 

ANSWER:   c

 

15. Which of the following is not a commonly used technique for protein isolation and purification?

  a. gas-liquid chromatography.
  b. ion exchange chromatography.
  c. electrophoresis.
  d. solubility (“salting in” and “salting out”).
  e. affinity chromatography.

 

ANSWER:   a

 

16. Even though acid hydrolysis of proteins is favored over basic hydrolysis, with acid hydrolysis ____ is destroyed and must be estimated by other means.

  a. Lys
  b. Leu
  c. Asp
  d. Cys
  e. Trp

 

ANSWER:   e

 

17. Amino acid analysis of a protein gives:

  a. the sequence of the protein.
  b. the number of residues of each amino acid in the protein.
  c. the molecular weight of the protein.
  d. the percentage or ratio of the various amino acids in the protein.
  e. an identification of the N-terminal and C-terminal amino acids.

 

ANSWER:   d

 

18. The amino acid sequence is NOT:

  a. a distinctive characteristic of a polypeptide.
  b. encoded by the nucleotide sequence of DNA.
  c. a form of genetic information.
  d. read from N-terminal end to C-terminal end.
  e. constant for proteins with the same function from different organisms.

 

ANSWER:   e

 

19. Edman degradation will:

  a. determine the C-terminal amino acid by using a carboxypeptidase.
  b. cleave the protein into a multitude of smaller peptides.
  c. compare overlapping sets of peptide fragments.
  d. determine the N-terminal amino acid.
  e. generate two different, but overlapping sets of peptide fragments.

 

ANSWER:   d

 

20. After treating a protein with trypsin, which of the following techniques could be used to determine its identity by peptide mass fingerprinting?

  a. NMR
  b. MALDI-TOF mass spectrometer
  c. HPLC
  d. gel electrophoresis
  e. none of the above

 

ANSWER:   b

 

21. Reaction of the peptide, ala-met-lys-ser, with phenylisothiocyanate (PITC) at pH 8.0 followed by mild acidification (first cycle of Edman method) would release:

  a. the labeled peptide ala-met-lys-ser-PTH.
  b. PTH-ala, PTH-ser, PTH-lys and PTH-met.
  c. PTH-ser and the peptide ala-met-lys.
  d. PTH-ala and the peptide met-lys-ser.
  e. All of the above.

 

ANSWER:   d

 

22. What is the product formed from the acid hydrolysis of a simple amide?

  a. acid & base
  b. aldehyde & alcohol
  c. acid & amine
  d. ester & alcohol
  e. amine & aldehyde

 

ANSWER:   c

 

23. Which of the following would not be a useful procedure for dissociating the subunits of a multimeric protein in order to sequence the individual subunits?

  a. Exposure to pH extremes (ie, pH 1 or pH 13).
  b. High salt concentrations.
  c. 6 N HCl at 110°C for 24 hours.
  d. 8 M urea.
  e. 6 M guanidinium chloride.

 

ANSWER:   c

 

24. Insulin is a polypeptide hormone that contains two short polypeptide chains linked by two interstrand disulfide bonds. The most logical order of events to perform in order to sequence this protein would be:

A. The peptides are reduced with mercaptoethanol.
B. The peptides are sequenced using Edman chemistry.
C. The peptides are separated by chromatography techniques.
D. The peptides are alkylated with iodoacetamide.

 

  a. A, D, C, B
  b. C, A, D, B
  c. C, B, A, D
  d. A, B, C, D
  e. A, C, D, B

 

ANSWER:   a

 

25. The C-terminal residue of a polypeptide can be determined by first cleaving the polypeptide with:

  a. chymotrypsin.
  b. carboxypeptidase.
  c. trypsin.
  d. CNBr.
  e. none of the above.

 

ANSWER:   b

 

26. ____ is specific in hydrolyzing only peptide bonds in which the carboxyl function is contributed by an arginine or a lysine residue.

  a. Chymotrypsin
  b. Carboxypeptidase
  c. Trypsin
  d. CNBr
  e. None of the above.

 

ANSWER:   c

 

27. The advantage of treating separate samples of a protein with two or more enzymes when sequencing a protein is that the products are:

  a. more homogeneous.
  b. sequenceable without further chromatography.
  c. fragments with the same N- and C-terminal amino acids.
  d. fragments with sequence overlaps.
  e. all are true.

 

ANSWER:   d

 

28. What is the overall net charge on the peptide lys-lys-ser-glu at pH 7.0?

  a. +2
  b. +1
  c. 0
  d. −1
  e. −2

 

ANSWER:   b

 

29. All of the statements about the peptide val-asp-trp-asn-ser are correct EXCEPT:

  a. This peptide would show a strong absorption band at 280 nm.
  b. Reaction with chymotrypsin would yield two peptides.
  c. To synthesize this peptide using the solid phase method of Merrifield, the amino acid directly attached to the resin would be valine.
  d. After the second round of Edman degradation using the reagent PITC, the PTH-amino acid residue released would be PTH-asp.
  e. The peptide would be converted to a dipeptide and a tripeptide by chymotrypsin.

 

ANSWER:   c

 

30. Which of the following would be a possible amino acid sequence for an oligopeptide given the experimental data below?

1. The amino acid composition is found to be [ala, lys, phe, met, cys, plus some decomposition products].
2. The peptide has a molecular weight around 700 Da and absorbs at 280 nm.
3. Treatment with carboxypeptidase results in tryptophan and a peptide.
4. CNBr treatment yields a tetrapeptide and a dipeptide.
5. Trypsin digestion produces an amino acid and a pentapeptide with met on the amino end.
6. Chymotrypsin digestion yields a dipeptide and a tetrapeptide.

 

  a. trp-lys-met-cys-met-ala
  b. lys-met-cys-phe-ala-trp
  c. trp-ala-phe-cys-met-lys
  d. lys-ala-cys-phe-met-trp
  e. lys-met-cys-ala-phe-trp

 

ANSWER:   b

 

31. The preponderance of protein sequence information is now derived from:

  a. chemical sequencing (Edman method).
  b. mass spectrometry.
  c. mass spectrometry-mass spectrometry.
  d. translating the nucleotide sequence of genes into codons, and thus amino acid sequence.
  e. none of the above.

 

ANSWER:   d

 

32. Homologous proteins such as hemoglobin from different organisms do NOT:

  a. have nearly identical lengths.
  b. share little sequence homology with other proteins with similar function (e.g., myoglobin).
  c. share a significant degree of sequence similarity.
  d. perform the same function in different organisms.
  e. have sequence identity in direct correlation to the relatedness of the species from which they were derived.

 

ANSWER:   b

 

33. Although they have very different functions, hen egg white lysozyme and ____ share similar sequence homology and similar tertiary structure.

  a. trypsin
  b. α-lactalbumin
  c. thrombin
  d. hemoglobin
  e. chymotrypsin

 

ANSWER:   b

 

34. The diversity in hemoglobin mutants indicates that:

  a. any amino acid change is relatively important.
  b. any amino acid change is lethal to the organism.
  c. specific amino acid changes drastically alter one or more functions of a protein.
  d. any amino acid change will have the same effect on the protein function.
  e. All are true.

 

ANSWER:   c

 

35. Proteins destined for an extracellular location are characteristically:

  a. phosphoproteins.
  b. glycoproteins.
  c. lipoproteins.
  d. nucleoproteins.
  e. flavoproteins.

 

ANSWER:   b

 

36. Proteins that do NOT perform any obvious chemical transformation, but control the ability of other proteins to carry out their physiological functions are:

  a. enzymes.
  b. regulatory proteins.
  c. transport proteins.
  d. storage proteins.
  e. structural proteins.

 

ANSWER:   b

 

37. Hemoglobin is an example of a(n):

  a. enzyme.
  b. regulatory protein.
  c. transport protein.
  d. storage protein.
  e. structural protein.

 

ANSWER:   c

 

38. Collagen is an example of a(n):

  a. enzyme.
  b. regulatory protein.
  c. transport protein.
  d. storage protein.
  e. structural protein.

 

ANSWER:   e

 

39. Which of the following reagents is correctly defined?

  a. iodoacetic acid:  reduces disulfide bonds
  b. guanadinium hydrochloride:  disrupts ionic interactions and hydrogen bonds
  c. phenylisothiocyanate:  reacts with free carboxyl groups
  d. cyanogen bromide:  reacts with internal cysteine residues
  e. performic acid:  reacts with free cysteine residues

 

ANSWER:   b

 

40. Which of the following protease enzymes is correctly identified with its specificity?

  a. trypsin:  cleaves on C-side of acidic amino acids
  b. chymotrypsin:  cleaves on C-side of aliphatic amino acids
  c. staphylococcal protease:  cleaves on C-side of acidic amino acids
  d. clostripain:  cleaves on C-side of lysine
  e. none of the above are correct

 

ANSWER:   c

 

41. Which of the following amino acids occurs most frequently in proteins?

  a. methionine
  b. alanine
  c. tryptophan
  d. tyrosine
  e. histidine

 

ANSWER:   b

 

42. Which of the following mutations would probably be least likely to impact the function of the protein?

  a. Lys to Ser
  b. Ala to Asp
  c. His to Pro
  d. Val to Ile
  e. Phe to Tyr

 

ANSWER:   d

 

43. Discuss the quaternary structure of proteins with an example.​

ANSWER:   Many proteins consist of two or more interacting polypeptide chains of characteristic tertiary structure, each of which is commonly referred to as a subunit of the protein. Subunit organization constitutes another level in the hierarchy of protein structure, defined as the protein’s quaternary (4°) structure. Questions of quaternary structure address the various kinds of subunits within a protein molecule, the number of each, and the ways in which they interact with one another. The α and β polypeptide chains of hemoglobin interact to form a quaternary structure.​
TOPICS:   5.1 What Architectural Arrangements Characterize Protein Structure?

 

44. ​Explain the role of trypsin in identifying the primary structure of a protein.

ANSWER:   Trypsin is a digestive enzyme that is used to produce polypeptide fragments useful for sequence analysis. Trypsin is the most commonly used reagent for specific proteolysis. Trypsin will only hydrolyze peptide bonds in which the carbonyl function is contributed by an arginine or a lysine residue. That is, trypsin cleaves on the C-side of Arginine (Arg) or Lysine (Lys), generating a set of peptide fragments having Arg or Lys at their C-termini. The number of smaller peptides resulting from trypsin action is equal to the total number of Arg and Lys residues in the protein plus one—the protein’s C-terminal peptide fragment.​
TOPICS:   5.4 How Is the Primary Structure of a Protein Determined?

 

45. Discuss the computer programs that can align amino acid sequences.​

ANSWER:   Protein sequence databases provide enormous resources for sequence comparisons. If two proteins share homology, it can be revealed through alignment of their sequences using powerful computer programs. In such studies, a given amino acid sequence is used to query the databases for proteins with similar sequences. BLAST (Basic Local Alignment Search Tool) is a commonly used program for rapid searching of sequence databases. The BLAST program detects local as well as global alignments where sequences are in close agreement. Even regions of similarity shared between otherwise unrelated proteins can be detected. Discovery of sequence similarities between proteins can help to guess the function of uncharacterized proteins and also to assign related proteins to protein families.​
TOPICS:   5.5 What Is the Nature of Amino Acid Sequences?

 

46. Discuss the biological functions of proteins.​

ANSWER:   Proteins fill essentially every biological role, with the exception of information storage. Binding proteins typically interact noncovalently with their specific ligands. Transport proteins—a class of binding proteins—include membrane proteins that transport substances across membranes, as well as soluble proteins that deliver specific nutrients or waste products throughout the body. Scaffold proteins are also binding proteins that use protein–protein interactions to recruit other proteins into multimeric assemblies that mediate and coordinate the flow of information in cells. Catalytic proteins (enzymes) mediate many metabolic reactions. Regulatory proteins that bind to specific nucleotide sequences within DNA control gene expression. Hormones—a kind of regulatory proteins—convey information about the environment to cells when they bind to specific receptors.​
TOPICS:   5.8 What Are the Many Biological Functions of Proteins?

 

47. Explain the significance of the proteome.​

ANSWER:   An accurate reflection of what a cell is doing at any moment in time is found in the proteome because proteins are the agents of cellular function. The full genetic potential of a cell (what it is capable of doing) is contained within its genome, but not all genes are expressed at any moment in time. The proteome is much more complex than the genome. While there are only 20,000 or so protein-coding genes in the human genome, estimates suggest that there are hundreds of thousands of different proteins, perhaps even a million or more. This discrepancy exists because one gene may give rise to a large number of protein products through a range of processes, such as post-translational modification or alternative RNA splicing or RNA editing.​
TOPICS:   5.9 What Is the Proteome and What Does It Tell Us?

 

 

 

 

1. Photosynthesis occurs in photosynthetic ____ localized in large organelles known as ____.

  a. membranes; chloroplasts
  b. proteins; ribosomes
  c. matrix; chloroplasts
  d. membranes; photoplasts
  e. none are true

 

ANSWER:   a

 

2. The reaction of photosynthesis whereby light energy is transduced into chemical energy uses ____ as a source of carbon, and produces ____.

  a. CO2; hexose
  b. hexose; CO2
  c. acetyl CoA; hexose
  d. CO2; acetyl CoA
  e. none of the above

 

ANSWER:   a

 

3. All are contained by chloroplasts EXCEPT:

  a. thylakoid membrane.
  b. ribosomes.
  c. DNA and RNA.
  d. stroma.
  e. all are true.

 

ANSWER:   e

 

4. Chloroplasts consist of a folded inner membrane called the ____, which is organized into paired folds called ____.

  a. thylakoid membrane; stroma
  b. lamellae; thylakoid membrane
  c. thylakoid membrane; lamellae
  d. stroma; thylakoid membrane
  e. lamellae; stroma

 

ANSWER:   c

 

5. Balance the following reaction:

____ NADPH + ____ H+ + ____ ATP + ____ CO2 + 12 H2 O → C6H12O6 + 12 NADP+ + 18 ADP + 18 Pi

  a. 6; 6; 18; 6
  b. 12; 12; 18; 3
  c. 6; 6; 12; 6
  d. 12; 12; 18; 6
  e. 6; 6; 12; 3

 

ANSWER:   d

 

6. Chloroplasts differ from mitochondria in that:

  a. chloroplasts can not generate ATP.
  b. only mitochondria have a double membrane.
  c. in chloroplasts, the proton gradient is generated between the thylakoid lumen and the stroma.
  d. only the mitochondrion has DNA, RNA and ribosomes.
  e. chloroplasts do not utilize a Q-cycle.

 

ANSWER:   c

 

7. Characteristics of chlorophyll include all EXCEPT:

  a. iron-containing porphyrin.
  b. planar conjugated porphyrin ring.
  c. long-chain phytol tail.
  d. delocalized π electrons in the aromatic ring.
  e. photoexcitable electrons.

 

ANSWER:   a

 

8. Carotenoids have primary roles in photosynthesis as:

  a. accessory light-harvesting and photooxidation.
  b. accessory light-harvesting and photoprotection from reactive oxygen species.
  c. resonance transfer pigments and photooxidation.
  d. resonance transfer and photodiffusion protection.
  e. none are true.

 

ANSWER:   b

 

9. Which of the following statements about the light reactions of photosynthesis is true?

  a. There are two distinct photosystems, linked together by a mechanism similar to electron transport.
  b. The source for electrons is located in the stroma of the thylakoid.
  c. The Mn complex is the primary electron acceptor and is located on photosystem I.
  d. The ultimate electron donor is molecular oxygen.
  e. Plastoquinone is a fixed electron transporter in the system located in the inner membrane.

 

ANSWER:   a

 

10. The light reactions in photosynthetic plants:

  a. reduce water to oxygen with the production of NADPH
  b. use NADP+ to oxidize water to oxygen, thus forming NADPH
  c. produce ATP and NADPH during cyclic photophosphorylation.
  d. involve the splitting of two water molecules to produce molecular oxygen.
  e. uses photons of visible light to effect the reduction of water to oxygen

 

ANSWER:   d

 

11. When light energy is absorbed by chlorophyll an electron is promoted to a higher orbital and then transferred to a suitable acceptor resulting in light energy conversion to chemical energy in a(n):

  a. isomerase reaction.
  b. mutase reaction.
  c. ligase reaction.
  d. oxidation-reduction reaction.
  e. none of the above.

 

ANSWER:   d

 

12. If A and B represent electron-transfer molecules adjacent to chlorophyll (Chl) in the membrane, fill in the reaction sequence:

  a. Chl; Chl; A−; Chl+; B−
  b. Chl*; Chl*; A−; Chl; B+
  c. Chl*; Chl*; A+; Chl−; B+
  d. Chl−; Chl−; A+; Chl; B−
  e. Chl−; Chl−; A−; Chl+; B−

 

ANSWER:   b

 

13. The photosynthetic unit includes all EXCEPT:

  a. antenna chlorophylls.
  b. the reactive center.
  c. oxidation of chlorophyll to a cationic free radical, Chl .+ .
  d. the cationic free radical is the Mg2+ ion.
  e. all are true.

 

ANSWER:   d

 

14. Properties of photosystem II (PSII) include all EXCEPT:

  a. light-driven O2 evolution.
  b. similar photosystem in photosynthetic bacteria.
  c. use quinines as terminal electron acceptors.
  d. found in cyanobacteria, green algae and higher plants.
  e. all are true.

 

ANSWER:   e

 

15. Chlorophyll is located in the ____ of the chloroplast.

  a. thylakoid membranes associated with proteins
  b. thylakoid spaces associated with rubisco
  c. stroma
  d. inner membrane space
  e. outer membrane

 

ANSWER:   a

 

16. Many chlorophyll molecules absorb light and direct the energy to the reactive centers. The transfer of this absorbed energy is called:

  a. fluorescence transfer.
  b. redox transfer.
  c. resonance energy transfer.
  d. photochemical emission.
  e. energy transduction.

 

ANSWER:   c

 

17. All of the following are involved in the production of biochemical energy from light EXCEPT:

  a. electron transfer.
  b. Q-cycle.
  c. transmembrane pH gradient.
  d. ribulose-1,5-bisphosphate.
  e. chlorophyll.

 

ANSWER:   d

 

18. How many photons of light must be absorbed by PSII for the oxidation of 2 water molecules to form one oxygen molecule?

  a. 2
  b. 4
  c. 6
  d. 8
  e. 16

 

ANSWER:   b

 

19. The essence of photosynthesis is the photochemical event which is:

  a. conversion of H2O to O2.
  b. reduction of NADP+.
  c. phosphorylation of ADP.
  d. light energy transduction to chemical energy.
  e. fixation of CO2.

 

ANSWER:   d

 

20. All are properties of both the P700 and P680 reaction centers EXCEPT:

  a. contain chlorophyll dimers.
  b. are electron donors.
  c. are activated by visible light.
  d. are involved in light-driven O2 evolution.
  e. all are properties.

 

ANSWER:   d

 

21. Via PSII and PSI, electrons ultimately flow from ____ to ____.

  a. NAPDH; O2
  b. NADP+; water
  c. water; NADP+
  d. O2; NADPH
  e. None are true

 

ANSWER:   c

 

22. The product(s) of the R. viridis photosynthetic reaction center is (are):

  a. mobile reduced quinone.
  b. NADPH.
  c. O2.
  d. reduced ferredoxin.
  e. protons.

 

ANSWER:   a

 

23. The quantum yield of photosynthesis can be defined as the amount of ____ formed per equivalent of ____.

  a. photons; light input
  b. product; light input
  c. ATP; coenzyme Q
  d. carbohydrate; ATP
  e. none are true

 

ANSWER:   b

 

24. Which statement regarding light is NOT true?

  a. the energy of a photon of light is calculated by E=hν
  b. the energy of 700nm light is greater than that of 400nm light
  c. photosynthesis allows two electrons to flow for each pair of photons absorbed per center
  d. the quantum yield of photosynthesis can be described as CO2 fixed per photon absorbed, or O2 evolved per photon absorbed
  e. none are true

 

ANSWER:   b

 

25. Photophosphorylation is the term for:

  a. activation of enzymes with light
  b. ATP synthesis driven by light energy
  c. dephosphorylation of ATP, resulting in a photon of light being released
  d. production of hexose from CO2
  e. none are true

 

ANSWER:   b

 

26. Photosynthetic phosphorylation and oxidative phosphorylation are similar processes. All of the following are common to BOTH processes EXCEPT:

  a. both have fixed and mobile electron carriers.
  b. both contain cytochromes in their electron carrier chains.
  c. both produce NADPH to be used in the reductive pentose phosphate pathway (Calvin cycle).
  d. both represent a major route of ATP synthesis.
  e. both have quinones as electron carriers.

 

ANSWER:   c

 

27. The proton-motive force is composed of a ____ and a ____, and in photophosphorylation the ____ is greater.

  a. pH gradient; ATP/H+ ratio; ATP/ H+ ratio
  b. ATP/ H+ ratio; ion equilibrium; ion equilibrium
  c. membrane potential; pH gradient; membrane potential
  d. membrane potential; pH gradient; pH gradient
  e. ATP/ H+ ratio; membrane potential; membrane potential

 

ANSWER:   d

 

28. Characteristics of the chloroplast’s ATP synthase include all EXCEPT:

  a. contains CF1CF0 complex.
  b. heteromultimer of subunits.
  c. imbedded in the thylakoid membrane.
  d. has 14 c-subunits in its F0 rotor.
  e. all are true.

 

ANSWER:   e

 

29. Cyclic photophosphorylation takes place when:

  a. there is not enough light to activate the PSII complex.
  b. NADPH is high, therefore energy is used to drive the citrate cycle.
  c. ferredoxin is used to reduce the Mn-cluster.
  d. the proton gradient is not high enough to go all the way through the system.
  e. NADPH/NADP+ ratio is high, energy is used in generating ATP.

 

ANSWER:   e

 

30. All are true for cyclic photophosphorylation EXCEPT:

  a. oxygen is evolved.
  b. utilizes cyt b6 of cyt f/cyt b6 complex.
  c. does not utilize ferredoxin.
  d. PS I is involved.
  e. all are true.

 

ANSWER:   a

 

31. Which of the following is an outcome of ferredoxin passing electrons to cytochrome f / cytochrome b6 complex?

  a. proton gradient formation
  b. ATP synthesis
  c. NADPH production
  d. oxygen evolution
  e. both A and B occur

 

ANSWER:   e

 

32. Light-dependent electron flow with the production of ATP can occur without the formation of NADPH. This process is called ____, which involves only one of the photosystems, ____.

  a. noncyclic photophosphorylation; P700
  b. cyclic photophosphorylation; P700
  c. noncyclic photophosphorylation; photosystem II
  d. noncyclic photophosphorylation; P680
  e. cyclic photophosphorylation; P680

 

ANSWER:   b

 

33. Which of the following is the product of cyclic photophosphorylation?

  a. NADPH
  b. Molecular oxygen
  c. ATP
  d. ADP and Pi
  e. Electron gradient

 

ANSWER:   c

 

34. ____ and ____ are produced in the light reactions of photosynthesis which are used to convert ____ to ____.

  a. ATP; NADPH; carbon dioxide; sugar
  b. oxygen; ATP; NADPH; carbon dioxide
  c. ATP; NADP+; carbon dioxide; sugar
  d. oxygen; NADPH; ATP; sugar
  e. NADPH; ATP; sugar; carbon dioxide

 

ANSWER:   a

 

35. Spinach chloroplasts are illuminated in the absence of ADP and Pi, then the light is turned off and ADP and Pi are added. ATP is then synthesized for a short time in the dark. Which of the following best explains this?

I. ATP is generated from the proton gradient accumulated in the light reactions.
II. ATP synthesis stops after the proton gradient dissipates.
III. ATP can be generated in the dark reactions if it becomes necessary for the plant to survive.

 

  a. I, III
  b. I only
  c. II only
  d. I, II
  e. II, III

 

ANSWER:   d

 

36. All are correct statements about rubisco EXCEPT:

  a. ribulose-1,5-bisphosphate and carbon dioxide are both substrates.
  b. the catalytic site has both carboxylase and oxygenase activity.
  c. it is found in the chloroplast stroma.
  d. it releases two molecules of glyceraldehyde-3-phosphate as products.
  e. it may be the most abundant enzyme in plants.

 

ANSWER:   d

 

37. The appropriate sequence of events for activation of rubisco is:

A. carboxylation of E
B. ribulose-1,5-bisphosphate released from E
C. rubisco activase
D. Mg2+ binding
E. light flash

 

  a. C, E, D, A, B
  b. C, D, A, B, E
  c. B, C, D, A, E
  d. E, B, C, D, A
  e. E, C, B, A, D

 

ANSWER:   e

 

38. Many of the enzymes of the Calvin cycle are also involved in ____; however, the glyceraldehyde-3-phosphate dehydrogenase of the Calvin cycle is specific for ____.

  a. glycolysis;  NADPH
  b. citric acid cycle;  NADH
  c. glycolysis; FADH2
  d. citric acid cycle,  NADPH
  e. none of the above

 

ANSWER:   a

 

39. All are correct about reactions of the Calvin cycle EXCEPT:

  a. ATP is hydrolyzed to ADP.
  b. NADP+ is reduced to NADPH.
  c. an intermediate is fructose-1,6-bisphosphate.
  d. some of the enzymes are shared by glycolysis.
  e. involves a ribulose-5-phosphate kinase.

 

ANSWER:   b

 

40. What type of enzyme catalyzes the reaction?

Erythrose-4-P + dihydroxyacetone phosphate (DHAP) ⇔ sedoheptulose-1,7-bisphosphate

  a. isomerase
  b. aldolase
  c. transaldolase
  d. transketolase
  e. mutase

 

ANSWER:   b

 

41. What type of enzyme catalyzes the reaction?

Sedoheptulose-1,7-bisphosphate + H2O ⇔ sedoheptulose-7-phosphate + Pi

  a. hydrolase
  b. isomerase
  c. aldolase
  d. mutase
  e. lyase

 

ANSWER:   a

 

42. What type of enzyme catalyzes the reaction?

sedoheptulose-7-P + glyceraldehyde-3-P ⇔ xylulose-5-P + ribose-5-P

  a. isomerase
  b. lyase
  c. transaldolase
  d. transketolase
  e. aldolase

 

ANSWER:   d

 

43. All of the following are accomplished in the dark reactions of photosynthesis EXCEPT:

  a. carbon dioxide is fixed to ribulose-1,5-bisphosphate.
  b. two molecules of 3-phosphoglycerate are produced.
  c. glyceraldehyde-3-phosphate is used to synthesize glucose.
  d. glyceraldehyde-3-phosphate is used to re-synthesize ribulose-1,5-bisphosphate.
  e. ATP is produced.

 

ANSWER:   e

 

44. The reaction, Ribulose-5-phosphate + ATP → Ribulose-1,5-bisphosphate + ADP, is catalyzed by:

  a. phosphopentose isomerase.
  b. phosphoribulose kinase.
  c. ribulose bisphosphate carboxylase.
  d. phosphopentose epimerase.
  e. transketolase.

 

ANSWER:   b

 

45. To avoid futile cycling of carbohydrates:

  a. CO2 fixation by Calvin cycle proceeds in the dark.
  b. citric acid cycle, glycolysis and oxidative phosphorylation are inhibited when light is present.
  c. the enzymes of the Calvin cycle are inhibited by light reactions.
  d. plants do not have glycolytic and citric acid cycle enzymes.
  e. none of the above.

 

ANSWER:   b

 

46. The light-induced changes in chloroplasts which regulate key Calvin cycle enzymes include all EXCEPT:

  a. activation of rubisco activase.
  b. Mg2+ efflux from the thylakoid lumen.
  c. changes in stromal pH.
  d. generation of reducing power.
  e. all are true.

 

ANSWER:   e

 

47. Although the ratio of carboxylase to oxygenase activity of rubisco is about ____ to one, the oxygenase activity diminishes plant productivity because of the loss of ____.

  a. one; rubisco
  b. two; ribulose-5-phosphate
  c. 3-4; ribulose-1,5-bisphosphate
  d. 6-8; rubisco
  e. 8-10; ribulose-5-phosphate

 

ANSWER:   c

 

48. How is photorespiration avoided in C-4 plants?

  a. decrease the concentration of phosphoglycolate.
  b. carry carbon dioxide towards an oxygen rich area of the plant.
  c. increase the concentration of ribulose-1,5-bisphosphate.
  d. transport of carbon dioxide from the mesophyll cells to the bundle sheath cells.
  e. none of the above.

 

ANSWER:   d

 

49. All of the following are characteristics of a C-4 plant EXCEPT:

  a. PEP carboxylase.
  b. transport of carbon dioxide and reducing power from the mesophyll cells to the bundle sheath cells.
  c. pyruvate-Pi dikinase.
  d. the expenditure of two high-energy phosphate bonds for each transport of carbon dioxide.
  e. carbon dioxide uptake in the daytime and fixation at night.

 

ANSWER:   e

 

50. The essential enzyme in C-4 plants used to conserve CO2 and avoid photophosphorylation is:

  a. rubisco.
  b. PEP carboxylase.
  c. glyceraldehyde-3-phosphate dehydrogenase.
  d. aldolase.
  e. ribulose-5-phosphate kinase.

 

ANSWER:   b

 

51. Which of the following set of pathways is similar between plants and animals?

I. electron transport and the dark reactions of photosynthesis
II. electron transport and the light reactions of photosynthesis
III. the Hatch-Slack pathway (C-4) and pyruvate carboxylase

 

  a. I only
  b. II only
  c. III only
  d. I, III
  e. II, III

 

ANSWER:   e

 

52. All of the following are characteristics of CAM plants EXCEPT:

  a. the stroma are open during the night and closed during the day.
  b. they try to avoid loss of water by evaporation.
  c. there is an accumulation of CO2 fixation into the organic acids OAA and malate.
  d. during the night, dicarboxylic acid are stored within the vacuoles.
  e. CO2 is fixed by rubisco during the night.

 

ANSWER:   e

 

53. CO2 fixation is one of the most critical reactions on earth.  Which of the following are elements of the reaction catalyzed by the RUBISCO enzyme?

  a. Mg2+ acts as a Lewis acid, binding to CO2 and making it more susceptible to nucleophilic attack
  b. The 6-carbon enzyme-bound intermediate that forms is split into 2 molecules of 3-phosphoglycerate
  c. Biotin is attached to a Lys residue in the active site and serves a critical role in the activation of CO2
  d. ATP is required for the activation of CO2 prior to its reaction with ribulose-1,5-bisphosphate
  e. Both a and b occur

 

ANSWER:   e

 

54. During photosynthesis-linked carbohydrate synthesis in plants, the products of photosynthesis are required for the actual fixation of carbon.  Which of the following correctly explains the use of the products of photosynthesis?

  a. NADPH is required for the actual reduction of CO2 by the RUBISCO enzyme.
  b. ATP is used primarily during the regeneration of ribulose-1,5-bisphosphate
  c. Oxygen is used during the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate
  d. Protons from the formation of the proton gradient are required to activate the RUBISCO enzyme
  e. Both A and B are correct

 

ANSWER:   b

 

55. Which of the following is true regarding CO2 fixation in plants?

  a. CAM plants work by storing carbon dioxide at night in the form of oxaloacetate
  b. The RUBISCO enzyme has a higher affinity for oxygen than for CO2, making it very difficult to effectively fix CO2
  c. At high temperatures, C4 plants are more efficient than C3 plants because they are able to fix CO2 with minimal photorespiration
  d. The RUBISCO enzyme contains a Mg2+ that acts as a Lewis base, binding to CO2 and making it more susceptible to nucleophilic attack
  e. None of the above are true

 

ANSWER:   c

 

56. The general flow of electrons in plant photosynthesis is from PSII to PSI.  Which of the following correctly explains the events that occur during this process?

  a. The oxidation of water occurs at PSI with the electrons being passed to ferredoxin to reduce NADP+.
  b. Protons are pumped into the lumen at PSII during water reduction and also by the cytochrome bf complex allowing for ATP synthesis to occur.
  c. A cyclic flow of electrons is created between ferredoxin, cytochrome bf complex, and PSI that allows for the production of NADPH without the generation of ATP.
  d. For each electron removed from a water molecule, 2 photons are required to transfer it to ferredoxin.
  e. None of the above

 

ANSWER:   d

 

57. A new photosystem from a plant with yellow-colored leaves was discovered to have a potential difference of 2.73 volts between the ground and excited states.  What wavelength of light is required to excite an electron in this photosystem?

  a. 228 nm
  b. 455 nm
  c. 683 nm
  d. 910 nm
  e. none of the above

 

ANSWER:   b

 

58. Discuss the general formulation of the overall reaction of photosynthesis as stated by van Niel.​

ANSWER:   ​A general formulation of the overall reaction of photosynthesis is given below.

Hydrogen                 Hydrogen                  Reduced                  Oxidized

                       acceptor                   donor                       acceptor                    donor

In photosynthetic bacteria, H2A is variously H2S (photosynthetic green and purple sulfur bacteria), isopropanol, or some similar oxidizable substrate. (CH2O) symbolizes a carbohydrate unit. In cyanobacteria and the eukaryotic photosynthetic cells of algae and higher plants, H2A is H2O, and 2A is O2.​

TOPICS:   21.1 What Are the General Properties of Photosynthesis?

 

59. Discuss the photosystem II supramolecular complex. ​

ANSWER:   Overall photosynthetic electron transfer is accomplished by three membrane-spanning supramolecular complexes composed of intrinsic and extrinsic polypeptides. The PSII complex—also referred to as the oxygen-evolving complex—is described as a light-driven water: plastoquinone oxidoreductase and is responsible for photolysis of water. PSII possesses a metal cluster containing 4 Mn atoms, 1 Ca atom, and 5 O atoms, and 4 associated H2O molecules. As P680 (the reaction center of PSII) undergoes four cycles of light-induced oxidation, four protons and four electrons are removed from two of the water molecules and their O atoms are joined to form O2. A tyrosyl side chain of the PSII complex mediates electron transfer between the Mn4CaO5 cluster and P680 (the reaction center of PSII).​
TOPICS:   21.3 What Kinds of Photosystems Are Used to Capture Light Energy?

 

60. Discuss the structure of a plant membrane protein supercomplex consisting of the PSI reaction center and its lightharvesting antenna LHC1 (light-harvesting complex 1).​

ANSWER:   ​A plant membrane protein supercomplex exists as a “monomer” composed of 17 distinct protein subunits and 193 prosthetic groups, including 173 chlorophylls, 2 phylloquinones, and 3 Fe4S4 clusters. The four LHC1 subunits form an arc around one side of the PSI reaction center. A second light-harvesting complex (LHC2) binds to another side. This plant PSI system, like all photosystems, is remarkably efficient, showing a quantum efficiency of nearly 1 (one electron transferred per photon falling anywhere within the supercomplex). The many Chl and other light-harvesting molecules of the supercomplex form an integrated network for highly efficient transfer of light energy into P700.
TOPICS:   21.4 What Is the Molecular Architecture of Photosynthetic Reaction Centers?

 

61. Compare the two modes of photophosphorylation.​

ANSWER:   Both modes of photophosphorylation are coupled to ATP synthesis. In noncyclic photophosphorylation, electrons activated by quanta at PSII and PSI flow from H2O to NADP+, with concomitant establishment of the proton-motive force driving ATP synthesis. O2 is evolved and NADP+ is reduced. In cyclic photophosphorylation, the “electron hole” in P700+ created by electron loss from P700 is filled not by an electron derived from H2O via PSII but by a cyclic pathway in which the photoexcited electron returns ultimately to P700+ (the PSI reaction center in excited state). ATP is the sole product of energy conversion. No NADPH is generated, and because PSII is not involved, no oxygen is evolved.​
TOPICS:   21.6 How Does Light Drive the Synthesis of ATP?

 

62. What purpose do the Calvin cycle enzymes serve?​

ANSWER:  

The Calvin cycle enzymes serve three important ends:

1. They constitute the predominant CO2 fixation pathway in nature.

2. They accomplish the reduction of 3-phosphoglycerate, the primary product of CO2 fixation, to glyceraldehyde-3-phosphate so that carbohydrate synthesis becomes feasible.

3. They catalyze reactions that transform three-carbon compounds into four-, five-, six-, and seven-carbon compounds.

Most of the enzymes mediating the reactions of the Calvin cycle also participate in glycolysis.

TOPICS:   21.7 How Is Carbon Dioxide Used to Make Organic Molecules?

 

 

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