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PCOM Biochemistry > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

The cell membrane A. is a watery gel in which structures are suspended B. contains the powerhouse of the cell. C. is the central government of the cell. D. protects the cell and acts as a filter. E. carries the cell’s hereditary information.

A

D. protects the cell and acts as a filter.

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2
Q
  1. Structurally, the plasma membrane A. contains some imbedded proteins. B. is composed of a bilayer of lipids. C. contains some carbohydrate molecules. D. contains some small holes, or pores. E. all of the above
A

E. all of the above

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3
Q
  1. Which one of the following statements correctly describes membrane structure? A. Most membrane constituents are fixed in a specific location in the membrane. B. The hydrophobic region of the membrane is located along the exposed outer surface. C. Membranes consist of a ‘sandwich’ of lipids on the outside and protein on the inside. D. Phospholipids are arranged with the fatty acids facing toward the center.
A

D. Phospholipids are arranged with the fatty acids facing toward the center.

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4
Q
  1. Which of the following best describes the lipid aggregates known as vesicles? A. They contain a hollow non-aqueous interior cavity. B. They are spherical structures with their hydrophobic regions aggregated in the interior cavity. C. They form because the cross-sectional area of the head group is greater than that of the acyl side chain(s). D. They are derived from a bilayer sheet.
A

D. They are derived from a bilayer sheet.

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5
Q
  1. Which of these functions might be expected for a membrane protein? A. serving as membrane receptors. B. transport of substances across the membrane. C. providing structure and support to the membrane. D. All of the above are functions of membrane proteins.
A

D. All of the above are functions of membrane proteins.

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6
Q
  1. Integral proteins associate with the membrane through A. covalent attachment to lipids. B. covalent attachment to lipid anchors such as palmitoyl groups. C. hydrophobic interactions with lipids. D. interactions with carbohydrates attached to lipids.
A

C. hydrophobic interactions with lipids.

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7
Q
  1. The most common way in which integral membrane proteins span the membrane is in A. α-helical segments. B. β-sheet structures. C. single strands with no secondary structure. D. alternate α-helical segments and β-sheet structures.
A

A. α-helical segments.

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8
Q
  1. The shortest  helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues. A. 5 B. 20 C. 50 D. 100
A

B. 20

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9
Q
  1. If a membrane protein in an intact erythrocyte reacts with a membrane-impermeable reagent, what can you conclude about the membrane protein? A. It is an integral membrane protein. B. It is a peripheral membrane protein. C. At least one domain of the protein is located on the outer face of the membrane. D. It is not a plasma membrane protein.
A

C. At least one domain of the protein is located on the outer face of the membrane.

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10
Q
  1. Peripheral membrane proteins A. can be extracted by chelating agents. B. completely span the membrane. C. are firmly associated with the membrane. D. can only be removed with detergents.
A

A. can be extracted by chelating agents.

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11
Q
  1. Which of the following is true about motion of membrane lipids? A. They can move most rapidly when in the gel phase. B. Lateral diffusion is catalyzed by flippase proteins. C. To increase the fluidity of membranes at low temperatures, cells synthesize more saturated fatty acids and fewer unsaturated fatty acids. D. Transbilayer diffusion involves the transfer of lipids from one face of the bilayer to another.
A

D. Transbilayer diffusion involves the transfer of lipids from one face of the bilayer to another.

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12
Q
  1. Considering membranes with phospholipids with these different average length fatty acids, which one would be expected to display the highest fluidity? A. 8 B. 10 C. 12 D. 14
A

A. 8

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13
Q
  1. Longer fatty acids make membranes less fluid because: A. the long chains tend to get interwined and tangled. B. this allows greater hydrogen-bonding between the methyl groups. C. longer fatty acids bind rather tenaciously to membrane proteins. D. there are more van der Waals interactions between the chains.
A

D. there are more van der Waals interactions between the chains.

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14
Q
  1. Considering membranes with phospholipids with fatty acids with these different average number of double bonds, which one would be expected to display the highest fluidity? A. 0 B. 1 C. 2 D. 3
A

D. 3

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15
Q
  1. More double-bonds in fatty acids make membranes more fluid because: A. fatty acids with lots of double bonds strongly repel each other. B. the fatty acids cannot not pack together as tightly. C. double bonds prevent cholesterol from entering the membrane. D. the phospholipids tend to flip-flop across the membrane more quickly.
A

B. the fatty acids cannot not pack together as tightly.

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16
Q
  1. When a bacterium such as E. coli is shifted from a warmer growth temperature to a cooler growth temperature, it compensates by: A. increasing its metabolic rate to generate more heat. B. putting longer-chain fatty acids into its membranes. C. putting more unsaturated fatty acids into its membranes. D. shifting from aerobic to anaerobic metabolism. E. synthesizing thicker membranes to insulate the cell.
A

C. putting more unsaturated fatty acids into its membranes.

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17
Q
  1. Cell membranes allow certain molecules to pass, while blocking others. This property is called A. impermeable. B. freely permeable. C. selectively permeable. D. actively permeable. E. none of the above
A

C. selectively permeable.

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18
Q
  1. By what mechanism would a nonpolar (hydrophobic) molecule move across a membrane if it is moving down its concentration gradient? A. facilitated diffusion B. cotransport C. simple diffusion D. active transport
A

C. simple diffusion

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19
Q
  1. By what mechanism would a polar (hydrophilic) molecule move across a membrane if it is moving down its concentration gradient? A. facilitated diffusion B. cotransport C. simple diffusion D. active transport
A

A. facilitated diffusion

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20
Q
  1. Facilitated diffusion differs from simple diffusion in that facilitated diffusion A. expends no ATP. B. moves molecules from an area of higher concentration to lower concentration. C. is dependent on carrier molecules. D. never eliminates the concentration gradient. E. is independent of carrier molecules.
A

C. is dependent on carrier molecules.

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21
Q
  1. Transporters can be divided into the categories of carriers and channels. Which of the following is true about the difference between carriers and channels? A. Carriers transport molecules across membranes faster than do channels. B. Carriers have greater stereospecificity for their substrates than do channels. C. Only carriers lower the free energy needed for transmembrane diffusion. D. Channels are more saturable than carriers.
A

B. Carriers have greater stereospecificity for their substrates than do channels.

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22
Q
  1. Which of the following statements is true about active transport? A. The transported species always moves against its electrochemical gradient. B. It is needed only for the transport of polar molecules. C. It is exergonic. D. It must be linked to ATP hydrolysis.
A

A. The transported species always moves against its electrochemical gradient.

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23
Q
  1. One difference between symport (SYNPORT) and antiport is that A. only antiport requires energy. B. only symport is reversible. C. only in antiport do two substrates move in opposite directions to each other. D. only symport is a cotransport system.
A

C. only in antiport do two substrates move in opposite directions to each other.

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24
Q
  1. Pumping of Na+ and K+ against concentration by Na+ K+ -ATPase is a typical example of A. Primary active transport B. Symport C. Antiport D. Passive transport
A

A. Primary active transport

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25
Q
  1. The chloride-bicarbonate exchanger can move HCO3 - and Cl- move in opposite directions. This is a typical example of A. Primary active transport B. Symport C. Antiport D. Passive transport
A

C. Antiport

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26
Q
  1. Each time, Na+ K+ -ATPase can A. Pump 3 Na+ out of the cell, and 2 K+ into the cell. B. Pump 3 Na+ into the cell, and 2 K+ out of the cell. C. Pump 2 Na+ out of the cell, and 3 K+ into the cell. D. Pump 2 Na+ into the cell, and 3 K+ out of the cell.
A

A. Pump 3 Na+ out of the cell, and 2 K+ into the cell.

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27
Q
  1. The final metabolite produced by glycolysis is: A. acetyl CoA. B. pyruvate. C. 3-phosphoglycerate. D. glyceraldehyde 3-phosphate. E. fatty acids.
A

B. pyruvate.

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28
Q
  1. The oxidation of sugars by glycolysis: A. occurs only in aerobic organisms. B. generates carbon dioxide. C. produces a net gain of ATP. D. occurs in mitochondria. E. uses NADH as a source of energy.
A

C. produces a net gain of ATP.

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29
Q
  1. In glycolysis, each molecule of glucose metabolized releases enough energy to form ________ molecules of ATP. A. 2 B. 4 C. 30 D. 36 E. 38
A

A. 2

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30
Q
  1. The enzymes that catalyze glycolysis are located in the A. cytosol B. nucleus C. mitochondrial matrix D. inner mitochondrial membrane E. endoplasmic reticulum
A

A. cytosol

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31
Q
  1. In which of the following metabolic conversions is ATP “consumed” during glycolysis? A. 1,3-Bisphosphoglycerate → 3-phosphoglycerate B. Glucose → glucose-6-phosphate C. 2-Phosphoglycerate → 3-phosphoglycerate D. Fructose-1,6-bisphosphate → dihydroxyacetone phosphate + glyceraldehyde-3- phosphate E. Glucose-6-phosphate → fructose-6-phosphate
A

B. Glucose → glucose-6-phosphate

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32
Q
  1. Which of the following enzymes catalyzes the transfer of a phosphoryl group from ATP to glucose? A. hexokinase B. phosphoglucose isomerase C. glucose-6-phosphatase D. phosphoglucose mutase E. aldolase
A

A. hexokinase

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33
Q
  1. What purpose is served by the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase as the first step in glycolysis? A. It helps cells keep glucose in the cytoplasm. B. It generates a high-energy phosphate bond. C. It converts ATP to a more useful form. D. It enables the glucose 6-phosphate to be recognized by phosphofructokinase, the next enzyme in the glycolytic pathway.
A

A. It helps cells keep glucose in the cytoplasm.

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34
Q
  1. Which reaction does the enzyme phosphoglucose isomerase catalyze? A. glucose  glucose 6-phosphate. B. fructose 6-phosphate  fructose 1,6-bisphosphate. C. glucose 6-phosphate  fructose 6-phosphate. D. glucose  glucose 1-phosphate. E. glucose  fructose.
A

C. glucose 6-phosphate  fructose 6-phosphate.

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35
Q
  1. During glycolysis, the steps between glucose and formation of the triose phosphates A. consume two ATP and two NADH molecules B. consume two ATP molecules C. produce two ADP and two NAD+ molecules D. produce two ATP and two NADH molecules E. consume two NADH molecules
A

B. consume two ATP molecules

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36
Q
  1. Which of the following enzymes control the entry of sugars into the glycolytic pathway? A. Hexokinase. B. Phosphofructokinase-1. C. Pyruvate dehydrogenase. D. Isocitrate dehydrogenase. E. Phosphoglucose isomerase.
A

B. Phosphofructokinase-1.

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37
Q
  1. Which of the following metabolic conversions is considered to be the major control point of glycolysis? A. Fructose-1,6-bisphosphate → dihydroxyacetone phosphate + glyceraldehyde-3- phosphate B. Glucose → glucose-6-phosphate C. 2-phosphoglyerate → phosphoenolpyruvate D. Fructose-6-phosphate → fructose-1,6-bisphosphate E. pyruvate → lactate
A

D. Fructose-6-phosphate → fructose-1,6-bisphosphate

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38
Q
  1. Phosphofructokinase-1 is allosterically inhibited by high concentrations of A. glucose B. ATP C. pyruvate D. fructose-6-phosphate E. None of the above
A

B. ATP

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39
Q
  1. What two 3-carbon molecules are generated by the cleavage of fructose-1,6-bisphosphate? A. glyceraldehyde-3-phosphate and 3-phosphoglycerate B. glyceraldehyde-3-phosphate and dihydroxyacetone phosphate C. pyruvate and phosphoenolpyruvate D. enolase and 2-phosphoglycerate E. glyceraldehyde-3-phosphate and pyruvate
A

B. glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

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40
Q
  1. What reaction is catalyzed by aldolase? A. isomerization of DHAP to GAP B. ligation of GAP and DHAP C. reversible cleavage of F-1,6-BP to DHAP and GAP D. cleavage of DHAP to GAP E. irreversible aldol condensation of DHAP and GAP
A

C. reversible cleavage of F-1,6-BP to DHAP and GAP

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41
Q
  1. What is the function of glyceraldehyde 3-phosphate dehydrogenase? A. oxidation by NAD+ and formation of acyl-phosphate B. oxidation of the alcohol to an aldehyde C. dehydration and dephosphorylation of GAP D. hydrolysis of GAP E. None of the above.
A

A. oxidation by NAD+ and formation of acyl-phosphate

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42
Q
  1. The process by which ATP is formed from ADP in glycolysis is referred to as A. oxidation B. reduction C. substrate-level phosphorylation D. oxidative phosphorylation E. photophosphorylation
A

C. substrate-level phosphorylation

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43
Q
  1. What is substrate level phosphorylation? A. phosphorylation of AMP by ATP B. ATP synthesis when the phosphate donor is a substrate with high phosphoryl transfer potential C. phosphorylation of glycolytic intermediates D. phosphorylation of ATP coupled to an ion gradient E. ATP and AMP synthesis from two molecules of ADP
A

B. ATP synthesis when the phosphate donor is a substrate with high phosphoryl transfer potential

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44
Q
  1. Which of the following enzymes is involved in substrate level phosphorylation in glycolysis? A. hexokinase B. pyruvate kinase C. glyceraldehyde-3phosphate dehydrogenase D. aldolase E. None of the above.
A

B. pyruvate kinase

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45
Q
  1. What are the primary metabolic fates of pyruvate? A. ethanol B. lactate C. acetyl CoA D. All of the above. E. None of the above.
A

D. All of the above.

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46
Q
  1. Glucose is converted to ______ in skeletal muscle under anaerobic conditions. A. lactate B. ethanol and carbon dioxide C. propionate D. glycogen E. acetyl-CoA
A

A. lactate

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47
Q
  1. In skeletal muscle cells, the NADH that is produced by glycolysis under anaerobic conditions (vigorous exercise) is regenerated to NAD+ by the conversion of: A. acetaldehyde → ethanol B. lactate → pyruvate C. phosphoenolpyruvate → pyruvate D. pyruvate → lactate E. glyceraldehyde-3-phosphate → 1,3-bisphosphoglycerate
A

D. pyruvate → lactate

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48
Q
  1. In anaerobic conditions, skeletal muscle produces: A. lactate and CO2. B. ethanol and CO2. C. lactate only. D. ethanol only. E. lactate, ethanol, and CO2.
A

C. lactate only.

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49
Q
  1. The infoldings of the inner mitochondrial membrane are called A. cisternae. B. cristae. C. laminae. D. lacunae.
A

A. cisternae.

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50
Q
  1. The inner compartment of mitochondria is called the A. stroma. B. intermembrane space. C. inner membrane space. D. matrix.
A

D. matrix.

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51
Q
  1. What product of glycolysis is transported into the mitochondria? A. Acetate as acetyl CoA B. Pyruvate C. Ethanol D. Lactic acid
A

B. Pyruvate

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52
Q
  1. Most small molecules are permeable across A. both mitochondrial membranes. B. the inner, but not the outer, mitochondrial membrane. C. the outer, but not the inner, mitochondrial membrane. D. neither mitochondrial membrane.
A

C. the outer, but not the inner, mitochondrial membrane.

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53
Q
  1. Which of the following statements about the mitochondrial inner membrane is FALSE? A. The inner membrane is permeable to CO2, H2O, and small ions. B. The inner membrane contains about 75% protein. C. The inner membrane contains many respiratory proteins. D. The inner membrane is highly invaginated.
A

A. The inner membrane is permeable to CO2, H2O, and small ions.

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54
Q
  1. The inner mitochondrial membrane contains proteins that A. synthesize ATP. B. pump protons. C. transport pyruvate and fatty acids. D. All of the above
A

D. All of the above

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55
Q
  1. Electron transport and oxidative phosphorylation are performed by protein complexes in the mitochondrial A. outer membrane. B. intermembrane space. C. inner membrane. D. matrix.
A

C. inner membrane.

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56
Q
  1. The electrons formed from the oxidation of glucose are A. directly transferred to O2 during the citric acid cycle. B. transferred to the coenzymes NAD+ and FAD. C. transferred to succinate and arachidonic acid. D. A and B E. none of the above
A

B. transferred to the coenzymes NAD+ and FAD.

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57
Q
  1. Several prosthetic groups act as redox centers in Complex I, including A. FMN, ubiquinone, iron-sulfur clusters, heme. B. FMN, ubiquinone, iron-sulfur clusters. C. heme, ubiquinone, iron-sulfur clusters. D. all of the above
A

B. FMN, ubiquinone, iron-sulfur clusters.

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58
Q
  1. Coenzyme Q carries electrons from complex _______ to complex _______. A. I; II B. II; III C. I; III D. III; IV
A

B. II; III C. I; III

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59
Q
  1. Cytochrome C carries electrons from complex _______ to complex _______. E. I; II F. II; III G. I; III H. III; IV
A

H. III; IV

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60
Q
  1. Which complex is unable to generate sufficient free energy to power ATP synthesis? A. Complex I B. Complex II C. Complex III D. Complex IV E. All the complexes are able to generate sufficient free energy.
A

B. Complex II

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61
Q
  1. Which statement concerning Complex II of the electron transport chain is false? A. This complex oxidizes FADH2 and reduces coenzyme Q. B. This complex includes a cytochrome heme. C. This complex includes Fe-S centers. D. This complex pumps protons from the matrix to the intermembrane space. E. This complex also oxidizes succinate to fumarate in the TCA cycle.
A

B. This complex includes a cytochrome heme. D. This complex pumps protons from the matrix to the intermembrane space.

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62
Q
  1. Peter Mitchell received the Nobel Prize in 1978 for his revolutionary hypothesis of oxidative phosphorylation called the _______ hypothesis. A. chemiosmotic B. substrate-level phosphorylation C. ATP synthase D. endosymbiotic
A

A. chemiosmotic

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63
Q
  1. Which of the following statements about the chemiosmotic theory is false? A. Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. B. Energy is conserved as a transmembrane pH gradient. C. Oxidative phosphorylation cannot occur in membrane-free preparations. D. The effect of uncoupling reagents is a consequence of their ability to carry protons through membranes. E. The membrane ATPase, which plays an important role in other hypotheses for energy coupling, has no significant role in the chemiosmotic theory.
A

E. The membrane ATPase, which plays an important role in other hypotheses for energy coupling, has no significant role in the chemiosmotic theory.

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64
Q
  1. Which of the following statements regarding electron transport are true? A. Only high-energy electrons from NADH can be used to drive the electron transport chain. B. The proteins involved in electron transport couple oxidation to phosphorylation in much the same way that glyceraldehyde 3-phosphate dehydrogenase couples oxidation and phosphorylation in glycolysis. C. Electron transport occurs only in eukaryotes. D. Molecular oxygen is required in order to donate electrons to the electron transport chain. E. Electrons passing along the electron transport chain move to successively lower energy states.
A

E. Electrons passing along the electron transport chain move to successively lower energy states.

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65
Q
  1. In the final stage of the oxidation of food molecules, a gradient of protons is formed across the inner mitochondrial membrane, which is normally impermeable to protons. If cells are exposed to an agent that causes the membrane to become freely permeable to protons, which of the following effects would you expect to observe? A. Cells would be completely unable to synthesize ATP. B. NADH would build up. C. Carbon dioxide production would cease. D. Consumption of oxygen would fall. E. The ratio of ATP to ADP in the cytoplasm would fall.
A

E. The ratio of ATP to ADP in the cytoplasm would fall.

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66
Q
  1. What type of gradient is critical to ATP formation by oxidative phosphorylation? A. sodium ion B. potassium ion C. chloride ion D. proton
A

D. proton

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67
Q
  1. Which of the following statements are true about oxidative phosphorylation? A. Electron transport provides energy to pump protons into the intermembrane space. B. An electrochemical gradient is formed across the inner mitochondrial membrane. C. Potassium and sodium ions form an ionic gradient across the inner mitochondrial membrane. D. A and B E. A, B, and C
A

D. A and B

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68
Q
  1. During oxidative phosphorylation, the proton motive force generated by electron transport is used to: A. create a pore in the inner mitochondrial membrane. B. generate the substrates (ADP and Pi) for the ATP synthase. C. induce a conformational change in the ATP synthase. D. oxidize NADH to NAD+. E. reduce O2 to H2O.
A

C. induce a conformational change in the ATP synthase.

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69
Q
  1. Electron flow down the electron-transport chain leads to the A. transport of protons across the inner mitochondrial membrane from inside the matrix to the intermembrane space. B. transport of protons across the inner mitochondrial membrane from the intermembrane space into the matrix. C. coupled synthesis of GTP. D. a dangerous imbalance of K+ ions across the mitochondiral membrane.
A

A. transport of protons across the inner mitochondrial membrane from inside the matrix to the intermembrane space.

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70
Q
  1. Complexes I and II each transfer electrons to A. NAD+ B. CoQ C. Cytochrome C D. O2
A

B. CoQ

71
Q
  1. The cytochromes contain _____ groups. A. NAD+ B. CoQ C. heme D. Fe-S centers
A

C. heme

72
Q
  1. Cytochrome c oxidase contains four redox centers, which include two ______ atoms which are unique to this complex. A. Cu B. Ca C. Fe D. S
A

A. Cu

73
Q
  1. Choose the correct path taken by a pair of electrons as it travels down the electron-transport chain. A. NADH → complex I → CoQ → Complex III → Cyt c → complex IV → O2 B. FADH2 → complex I → CoQ → Complex III → Cyt c → complex IV → O2 C. NADH → complex I → complex II→ Complex III → Cyt c → complex IV → O2 D. FADH2 → complex II → CoQ → Complex III → Cyt c → complex IV → O2 E. a and d
A

E. a and d

74
Q
  1. How many ATP molecules are synthesized from the oxidation of 1 NADH molecule? A. 1 B. 1.5 C. 2 D. 2.5 E. 3
A

D. 2.5

75
Q
  1. Oxidative phosphorylation is regulated by A. the availability of reduced cofactors from catabolic pathways. B. the availability of the dNTPs. C. the availability of ADP and Pi. D. A and C E. A, B, and C
A

D. A and C

76
Q
  1. The relative concentrations of ATP and ADP control the cellular rates of: A. glycolysis. B. oxidative phosphorylation. C. pyruvate oxidation. D. the citric acid cycle. E. all of the above.
A

E. all of the above.

77
Q
  1. Cyanide inhibits electron transport at A. Complex I B. Complex II C. Complex III D. Complex IV E. Complex V
A

D. Complex IV

78
Q
  1. Rotenone inhibits electron transport at A. Complex I B. Complex II C. Complex III D. Complex IV E. Complex V
A

A. Complex I

79
Q
  1. Oligomycin inhibits oxidative phosphorylation at A. Complex I B. Complex II C. Complex III D. Complex IV E. Complex V
A

E. Complex V

80
Q
  1. What is the chemical effect of oligomycin on aerobic metabolism? A. The flow of electrons from NADH to CoQ is blocked. B. The flow of electrons from Cyt c to oxygen is blocked. C. Oligomycin blocks the proton transfer through Fo of ATP synthase and therefore blocks the phosphorylation of ADP to form ATP. D. The transport of ATP out of and ADP into the mitochondria is blocked. E. Oxidative phosphorylation is uncoupled from electron transport and all the energy is lost as heat.
A

C. Oligomycin blocks the proton transfer through Fo of ATP synthase and therefore blocks the phosphorylation of ADP to form ATP.

81
Q
  1. Which of the following is an uncoupler for oxidative phosphorylation? A. Rotenone B. Cabon Monoxide C. Cyanide D. Dinitrophenol E. Oligomycin
A

D. Dinitrophenol

82
Q
  1. Cyanide, oligomycin, and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial oxidative phosphorylation. Which of the following statements correctly describes the mode of action of the three inhibitors? A. Cyanide and 2,4-dinitrophenol inhibit the respiratory chain, and oligomycin inhibits the synthesis of ATP. B. Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit the synthesis of ATP. C. Cyanide, oligomycin, and 2,4-dinitrophenol compete with O2 for cytochrome oxidase (Complex IV). D. Oligomycin and cyanide inhibit synthesis of ATP; 2,4-dinitrophenol inhibits the respiratory chain. E. Oligomycin inhibits the respiratory chain, whereas cyanide and 2,4-dinitrophenol prevent the synthesis of ATP.
A

B. Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit the synthesis of ATP.

83
Q
  1. 2,4-Dinitrophenol (DNP) and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4- Dinitrophenol is an uncoupling agent; oligomycin blocks the ATP synthesis reaction itself. Therefore, 2,4-dinitrophenol will: A. allow electron transfer in the presence of oligomycin. B. allow oxidative phosphorylation in the presence of oligomycin. C. block electron transfer in the presence of oligomycin. D. diminish O2 consumption in the presence of oligomycin
A

A. allow electron transfer in the presence of oligomycin.

84
Q
  1. Which of the following statements about energy conservation in the mitochondrion is false? A. Drug that inhibits the ATP synthase will also inhibit the flow of electrons down the chain of carriers. B. For oxidative phosphorylation to occur, it is essential to have a closed membranous structure with an inside and an outside. C. Uncouplers (such as dinitrophenol) have exactly the same effect on electron transfer as inhibitors such as cyanide; both block further electron transfer to oxygen. D. Uncouplers “short circuit” the proton gradient, thereby dissipating the proton motive force as heat.
A

A. Drug that inhibits the ATP synthase will also inhibit the flow of electrons down the chain of carriers.

85
Q
  1. What is the immediate result of the reaction catalyzed by superoxide dismutase? A. Conversion of the free radical O2 – to H2O2. B. Conversion of the free radical O2 – to H2O. C. Conversion of the free radical O2 – to CO2. D. Conversion of the free radical O2 – to CO.
A

A. Conversion of the free radical O2 – to H2O2.

86
Q
  1. New born babies produce heat by using the endogenous uncoupling agent: A. the small molecule 2-4-Dinitrophenol synthesized by the cell. B. the protein thermogenin. C. the protein thioredoxin. D. the protein cytochrome c. E. a modified form of the F0F1 ATPase.
A

B. the protein thermogenin.

87
Q
  1. Newborns generate heat by nonshivering thermogenesis that occurs in ______ tissue. A. muscle B. liver C. pancreatic D. brown adipose (fat) E. white adipose tissue
A

D. brown adipose (fat)

88
Q
  1. Which of the following is true about cofactors that are essential to the activity of some enzymes?
A

Answer: Cofactors that are covalently bound to an enzyme protein are called prosthetic groups.

89
Q
  1. A simple plot of V0 versus [S] is superior to a double-reciprocal plot (1/Vo versus 1/[S]) if you are trying to
A

Answer: detect allosteric regulation

90
Q
  1. In the double-reciprocal plot, increasing the concentration of inhibitor
A

Answer: lowers the Km

91
Q
  1. In competitive inhibition, increasing concentrations of the inhibitor will have the following effect on the kinetics of the enzyme
A

Answer: Vmax will stay the same

92
Q
  1. Which of the following is true about zymogens?
A

Answer: Zymogens are enzymatically inactive.

93
Q
  1. Which of the following is true about the phosphorylation of proteins
A

Answer: Proteins are usually phosphorylated at amino acids that have hydroxyl group-containing side chains.

94
Q
  1. In feedback inhibition
A

Answer: the end product of a pathway inhibits one of the enzymes in the pathway.

95
Q
  1. Which of the following enzymes fits in the class of enzymes known as hydrolases?
A

Answer: chymotrypsin

96
Q
  1. Which of the following is true about the role of enzymes in catalyzing chemical reactions?
A

Answer: Enzymes enhance the rate of reactions.

97
Q
  1. Which of the following is true about the free-energy changes involved in reactions that favor the formation of product?
A

Answer: The ground state free energy of the product must be lower than the ground state free energy of the substrate

98
Q
  1. In what way does the binding of a substrate by an enzyme enhance catalysis
A

Answer: The binding energy of the enzyme-substrate interaction lowers the activation energy.

99
Q
  1. An enzyme with a high turnover number has
A

Answer: a high Kcat

100
Q
  1. Which of the following is true about allosteric enzymes?
A

Answer: Allosteric enzymes always change the conformation of the active site in response to binding of an allosteric modulator.

101
Q
  1. Which of the following is true about general acid-base catalysis?
A

Answer: Amino acid side chains on enzymes can act as proton donors or acceptors

102
Q
  1. The steady state of an enzyme-catalyzed reaction is reached when
A

Answer: the concentration of the enzyme-substrate complex is constant over time.

103
Q
  1. The active site of an enzyme is most complimentary to
A

Answer: the transition state

104
Q
  1. The plasma membrane Ca2+ pump
A

Answer: keeps a low concentration of Ca2+ in the cytosol

105
Q
  1. All ion-transporting ATPases
A

Answer: engage in primary active transport.

106
Q
  1. Which process does not generate CO2?
A

Answer: the conversion of pyruvate to lactic acid

107
Q
  1. Which of the following is true about the fermentation of glucose?
A

Answer: The hydrogen to carbon ratio (H:C) of the reactants and products remains the same

108
Q
  1. Glycogen is degraded in a
A

Answer: phosphorolysis reaction

109
Q
  1. Which of the following sugars does not get converted to D-glucose before entering the glycolytic pathway?
A

Answer: D-fructose

110
Q
  1. Which of the following steps occurs during the payoff phase of glycolysis?
A

Answer: the conversion of phosphoenolpyruvate to pyruvate

111
Q
  1. Under what conditions will lactic acid accumulate in skeletal muscle?
A

Answer: when O2 is depleted

112
Q
  1. The enzyme that converts 3-phosphoglycerate to 2-phosphoglycerate is a
A

Answer: mutase

113
Q
  1. What is the role of uridine diphosphate (UDP) in the conversion of galactose to glucose 1-phosphate?
A

Answer: It serves as a carrier for galactose and glucose.

114
Q
  1. The NADPH produced in the pentose phosphate pathway is used
A

Answer: to provide reducing power for biosynthetic reactions.

115
Q
  1. Which of the following is true about gluconeogenesis?
A

In mammals, gluconeogenesis occurs predominately in the liver.

116
Q
  1. Rapidly dividing cells have a high need for nucleotide precursors, which are provided by
A

Answer: the pentose phosphate pathway

117
Q

All of the bypass reactions used in gluconeogenesis

A

Answer: are irreversible

118
Q
  1. Mammals cannot convert fatty acids to glucose because
A

Answer: they cannot convert acetyl-CoA to pyruvate.

119
Q
  1. Cellular respiration is the process by which cells
A

Answer: consume O2 and produce CO2.

120
Q
  1. Amino acids, fatty acids, and glucose are oxidized and enter the citric acid cycle as
A

Answer: acetyl-CoA.

121
Q
  1. The first reaction of the citric acid cycle, which generates citrate, is
A

Answer: a condensation reaction

122
Q

. For every molecule of glucose, how many molecules of CO2 are released in the citric acid cycle?

A

Answer: four

123
Q
  1. Which of the following is true about the pyruvate dehydrogenase complex?
A

Answer: It catalyzes oxidative decarboxylation.

124
Q
  1. What role does coenzyme A play in the citric acid cycle?
A

Answer: It is an acyl group carrier

125
Q
  1. Which of following is true about all of the dehydrogenase enzymes that participate in the citric acid cycle?
A

Answer: They generate reduced electron carriers.

126
Q
  1. What types of reactions do phosphorylases catalyze?
A

Answer: Displacement reactions in which an attacking phosphate becomes covalently attached at the point of bond breakage

127
Q
  1. Which of the following enzymes catalyzes a condensation reaction in which no nucleoside triphosphate is required as an energy source?
A

Answer: synthases

128
Q
  1. Which of the following conditions has a negative effect on the pyruvate dehydrogenase complex?
A

Answer: a high ratio of [acetyl-CoA]/[CoA]

129
Q
  1. In non-vertebrate organisms, the glyoxylate cycle is needed to convert
A

Answer: acetate to carbohydrates.

130
Q
  1. In what way are the glyoxylate cycle and citric acid cycles linked?
A

Answer: Succinate produced in the glycoxylate cycle enters the citric acid cycle.

131
Q
  1. The citric acid cycle is an amphibolic pathway, which means that
A

Answer: it serves in both anabolic and catabolic processes

132
Q
  1. Biotin
A

Answer: carries CO2 groups.

133
Q
  1. Which of the following citric acid cycle reaction steps is not inhibited by a high [NADH]/[NAD+]?
A

Answer: conversion of succinyl-CoA to succinate

134
Q
  1. Some plants that have been genetically engineered to express elevated levels of citrate synthase have increased crop productivity because
A

Answer: citric acid chelates metal ions

135
Q
  1. Anaplerotic reactions, such as the conversion of pyruvate to oxaloacetate, are useful to the citric acid cycle because they
A

Answer: generate a steady supply of intermediates for the citric acid cycle.

136
Q
  1. Which of the following is true of the properties oftriacylglycerols?
A

Answer: They generate more energy than the same weight of carbohydrate.

137
Q
  1. Ingested triacylglycerols are emulsified in the intestine by
A

Answer: bile salts.

138
Q
  1. What effect does the hormone glucagon have on fatty acid metabolism?
A

Answer: It triggers the mobilization of stored fats.

139
Q
  1. Which of the following is true of acyl-CoA synthetases?
A

Answer: They activate fatty acids for oxidation.

140
Q
  1. Carnitine is used
A

Answer: for transport of fatty acids across the inner mitochondrial membrane

141
Q
  1. The first step of β-oxidation, catalyzed by acyl-CoA dehydrogenase, involves
A

Answer: the formation of a double bond.

142
Q
  1. Complete β-oxidation of a 16-carbon saturated fatty acid
A

Answer: generates eight molecules of acetyl-CoA

143
Q
  1. Enoyl-CoA isomerase is needed for the complete β-oxidation of
A

Answer: unsaturated fatty acids with cis double bonds

144
Q
  1. The propionyl-CoA produced by β-oxidation of long-chain odd-number fatty acids enters the citric acid cycle as
A

Answer: succinyl-CoA

145
Q
  1. Both ω-oxidation and β-oxidation of fatty acids in animals
A

Answer: generate NADH.

146
Q
  1. After triacylglycerols are hydrolyzed into free fatty acids and glycerol, how is glycerol used for energy?
A

Answer: It enters the glycolysis pathway.

147
Q
  1. Which of the following is true about ketone bodies?
A

Answer: They are water-soluble

148
Q
  1. Ketone bodies are formed in
A

Answer: hepatocytes

149
Q
  1. What happens to ketone bodies after they are synthesized
A

Answer: They are exported to tissues.

150
Q
  1. Linoleate and α-linolenate are “essential fatty acids” because
A

Answer: mammals cannot introduce more than one double bond in fatty acid chains.

151
Q
  1. What is the function of eicosanoids?
A

Answer: They are signaling molecules.

152
Q
  1. Which of the following is true about fatty acid synthase of vertebrates?
A

Answer: It has a flexible phosphopantetheine arm

153
Q
  1. In animal cells, where does fatty acid synthesis occur?
A

Answer: in the cytosol

154
Q
  1. Which of the following occurs during the first cycle of fatty acid chain synthesis?
A

Answer: The malonyl group from malonyl-CoA is transferred to the acyl carrier protein (ACP).

155
Q
  1. In animals, what is the source of acetyl-CoA used in fatty acid synthesis?
A

Answer: citrate

156
Q
  1. What is the rate-limiting step in fatty acid synthesis?
A

Answer: the formation of malonyl-CoA

157
Q
  1. Fatty acyl-CoA desaturase, which introduces a double bond in a saturated fatty acid, is a(n)
A

Answer: mixed-function oxidase.

158
Q
  1. Which of the following is true about triacylglycerols?
A

Answer: They are derived from phosphatidic acid.

159
Q
  1. Which of the following is true about the regulation of triacylglycerol metabolism?
A

Answer: People with severe diabetes mellitus fail to synthesize fatty acids from carbohydrates

160
Q
  1. How does aspirin reduce inflammation?
A

Answer: It inhibits the formation of prostaglandins.

161
Q
  1. All sterols
A

Answer: are alcohols.

162
Q
  1. Squalene, the 30-carbon precursor of cholesterol, is composed of
A

Answer: six isoprene units

163
Q
  1. Chylomicrons
A

Answer: are synthesized in the small intestine.

164
Q
  1. Which of the following lipoproteins participates in reverse cholesterol transport?
A

Answer: HDL

165
Q
  1. Which of the following is true about glycerophospholipids?
A

Answer: They have a head group joined by a phosphodiesterlinkage.

166
Q
  1. Which of the following lipids or lipid-derived molecules has a glycerol backbone?
A

Answer: plasmalogen

167
Q
  1. Which of the following occurs when cholesterol enters cells?
A

Answer: Cholesterol is released from LDL particles when the particles become internalized by lysosomes.

168
Q
A
  1. Condensation
    2a. Dehydration
    2b. Hydration
  2. Oxidative Decarboxylation
  3. Oxidative Decarboxylation
  4. Substrate-level phosphorylation
  5. Dehydrogenation
  6. Hydration
  7. Dehydrogenation
169
Q
A
170
Q
A
171
Q

List main classes of enzymes and their functions

A
  1. Oxidoreductases - transfer electrons (hydride ion or H atoms) 2. Transfarases - group transfer reaction 3. Hydrolases - Hydrolysis reaction (transfer of functional group to water) 4. Lyases - Additions of fouls to double bonds, or formation of double bonds by removal of groups 5. Isomerase - Transfer of groups within molecules to yield some isomeric ions 6. Ligase - Formation of C-C, C-S, C-N, & C-O bonds by condensation reactions coupled to cleavage of ATP or similar cofactors. •Named by adding suffix “-ase” (describing the name of the substrate or enzyme’s function)
172
Q

Explain the bioenergetic basis for enzyme action

A
  1. Subtracted binds to active site on an enzyme. 2. An intermediate is formed between substrate and enzyme. (Go from substrate & enzyme to an intermediate form energy is released from this formation of the two) 3. An reaction inside the enzyme occurs. 4. After the reaction has taken place a product is formed. (Lower activation energy once product is released)
173
Q

Define the terms V0, Vmax , Km, and Kcat

A

Enzyme Kinetics: Determines the rate of a reaction Initial velocity (V0) increases with the increase in [S] Finally reaches the plateau (no V0) is called maximum velocity (Vmax), ( E + S <== K - 1 or K1 ==> ES = K2 => E + 2

PCOM Biochemistry (2 decks)

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