Biochemistry MCQs Flashcards by Amy McGovern

Adenosine diphosphate is formed by…
a. A reaction between a phosphorylated compound and adenosine diphosphate
b. In aerobic metabolism and not anaerobic metabolism
c. By adenosine and 2 phosphate molecules
d. A reaction between a phosphorylated compound and adenosine monophosphate

How well did you know this?

Not at all

Perfectly

A peptidase is an example of what type of enzyme?
a. Lyase
b. Transferase
c. Oxidoreductase
d. Hydrolase

How well did you know this?

Not at all

Perfectly

In the induced fit model of enzymatic activity….
a. The binding of the enzyme to the substrate does not affect the structure of the substrate
b. The conformation of the active site is rigid
c. Binding of the substrate to a flexible enzyme active site results in changes in the structure of the substrate
d. The complimentary shapes of the active site of the enzyme and the substrate are responsible for the catalytic activity of the enzyme

How well did you know this?

Not at all

Perfectly

pH has a profound effect on the catalytic effect of enzymes because…
a. It causes competitive inhibitors to bind to the active site
b. It makes co-factors available to the enzyme thus converting it to its active form
c. pH causes the substrate to degrade
d. pH affects the conformation at the active site and thus the ability of the enzyme to bind the substrate

How well did you know this?

Not at all

Perfectly

Which of the following statements about enzyme catalysed reactions is true?
a. Enzymes do not form complexes with their substrates
b. Enzymes alter the activation energy of a reaction
c. Enzyme catalysis is not influenced by pH
d. Enzymes are not involved in the digestion of food

How well did you know this?

Not at all

Perfectly

In which section of the human digestive tract does the digestion of polypeptides take place?
a. Small intestine
b. Stomach
c. Mouth
d. Duodenum

How well did you know this?

Not at all

Perfectly

The enzyme trypsin acts on which substrate and can be classified as what type of enzyme?
a. Proteins, hydrolase
b. Dextrans, reductase
c. Peptides, hydrolase
d. Amino acids, ligase

How well did you know this?

Not at all

Perfectly

What have carbohydrates been catabolised into by the time they enter the small intestine?
a. Polysaccharides
b. Starches
c. Monosaccharides
d. Disaccharides

How well did you know this?

Not at all

Perfectly

The loss and gain of electrons is what type of chemical reaction?
a. Reduction
b. Oxidation
c. Redox
d. Condensation

How well did you know this?

Not at all

Perfectly

Which of the following reactions in glycolysis, does not yield ATP?
a. Glyceraldehyde-3-phosphate  1,3 biphosphoglycerate
b. Phosphoelnolpyruvate (PEP)  pyruvate
c. 1,3 biphosphoglycerate  3-phosphoglycerate
d. B and C

How well did you know this?

Not at all

Perfectly

Which reaction in the gluconeogenesis pathway occurs in the mitochondria and not in the cytosol?
a. Fructose-1,6-biphosphate  fructose-6-phosphate
b. Pyruvate  oxaloacetate
c. Glucose-6-phosphate  glucose
d. Oxaloacetate  PEP

How well did you know this?

Not at all

Perfectly

Approximately how many proteins are required to facilitate the reaction below?
6CO2 + 12H2O + Light  C6H12O6 + 6O2 + 6H2O
a. 1
b. 20
c. 30
d. 15

How well did you know this?

Not at all

Perfectly

What process provides the electrons to replace those lost in Photosystem II in photosynthesis?
a. The electron transport chain
b. Cellular respiration
c. Proton flow
d. The splitting of water

How well did you know this?

Not at all

Perfectly

What is the overall energy yield from the oxidation of 1 molecule of behenic acid (C22:0)?
a. 126
b. 136
c. 150
d. 164

How well did you know this?

Not at all

Perfectly

In gluconeogenesis how many ATP molecules (or equivalents) are used in the conversion of pyruvate to glucose?
a. 4
b. 2
c. None
d. 6

How well did you know this?

Not at all

Perfectly

Where in the cell does chemiosmosis take place?
a. The cytosol
b. The chloroplast and the mitochondria
c. The nucleus and the cytosol
d. The mitochondria only

How well did you know this?

Not at all

Perfectly

Which enzymes breaks proteins into peptides?
a. Pepsin
b. Isomerases
c. Lyases
d. Maltase

How well did you know this?

Not at all

Perfectly

Which part of the ruminant digestive system is very similar to the stomach of non-ruminants?
a. Abomasum
b. Omasum
c. Reticulum
d. Rumen

How well did you know this?

Not at all

Perfectly

Which of the following is NOT a characteristic of allosterically regulated enzymes?
a. They bind to the active site of the enzyme
b. They are not influenced by the concentration of the enzyme
c. Allosteric regulation can involve either stimulation and inhibition of enzyme activity
d. Their effect is not reversed by adding substrate

How well did you know this?

Not at all

Perfectly

What type of enzyme could be described as an enzyme which catalyses the conversion of a molecule into an isomer?
a. Isomerase
b. Hydrolase
c. Lyase
d. Oxidoreductase

How well did you know this?

Not at all

Perfectly

In the lining of the stomach wall what type of cell is responsible for the production of hydrochloric acid?
a. Mucous cells
b. Gastric cells
c. Parietal cells
d. Chief cells

How well did you know this?

Not at all

Perfectly

How many rounds of β-oxidation are necessary to completely oxidise lignoceric acid (C24:0) to acetyl CoA?
a. 12
b. 8
c. 11
d. 24

How well did you know this?

Not at all

Perfectly

What metabolic process does the equation below summarise?
(Glucose)n + glucose + 2ATP + H2O  (Glucose)n+1 + 2ADP + 2Pi + 2H+
a. Glycogenesis
b. Glycolysis
c. Gluconeogenesis

How well did you know this?

Not at all

Perfectly

Which receptor is responsible for the uptake of chylomicron remnants by the liver?
a. apoCII
b. apoB-100
c. apoB-48
d. apo-E

How well did you know this?

Not at all

Perfectly

11. The equation below can be used to represent which biosynthetic process? 2H2O + 8 photons + 2NADP + ~3ADP + ~3Pi O2 + ~3ATP + 2NADPH a. Substrate level phosphorylation b. Photophosphorylation c. The Calvin Cycle

12. Per molecule of glucose how many ATP (or equivalents) are formed by substrate level phosphorylation in the pay-off phase of glycolysis? a. None b. 4 c. 6 d. 2

13. Which of the enzymes below has a role in glycolysis and gluconeogenesis? a. Glucose-6-phosphatase b. Phosphofructokinase c. Fructose-1,6-phosphatase d. Phosphoglycerate kinase

14. The conversion of glucose-6-phosphate to glucose-1-phosphate occurs in which metabolic process and is catalysed by which enzyme? a. Glucose-6-Phosphatase, glycogenolysis b. Phosphoglucomutase, glycogenolysis c. Phosphoglucomutase, glycogenesis d. Glycogen Phosphorylase, glycogenolysis

15. Which of the following is not one function of adenosine triphosphate in the cell? a. As a storehouse for energy b. Transport work c. Mechanical work

16. A ketogenic amino acid is a molecule… a. Whose carbon skeleton can be degraded to pyruvate b. That can be degraded to glucose c. That upon a series of catabolic reactions will yield acetyl-CoA d. Cannot be used as a source of energy

17. If [NADH] mitochondria is lower than the [NADH] cytosol then electrons from glycolysis are passed to _______ shuttle resulting in the formation of _______ ATP? a. Malate aspartate, 2.5 ATP b. Glycerol phosphate, 1.5 ATP c. Glycerol phosphate, 2.5 ATP d. Malate aspartate, 1.5 ATP

18. What will the absence of Malonyl CoA in a hepatocyte have on the extent of ketogenesis? a. Stimulates the activity of CPT I, dampens down the extent of ketogenesis b. Inhibits the activity of CPT I, dampens down the extent of ketogenesis c. Inhibits the activity of CPT I, increases the extent of ketogenesis d. Stimulates the activity of CPT I, increases the extent of ketogenesis

19. Which of these equations can be used to represent the formation of palmitate? a. 8Acetyl-CoA + 7ATP + 14NADPH + 14H+  palmitate + 8CoA + 7ADP + 7Pi + 14NADP+ + 6H2O b. 7Acetyl-CoA + 7CO2 + 7ATP  7malonyl-CoA + 7ADP + 7Pi c. Acetyl-CoA + 7ATP + 14NADPH + 14H+  palmitate + 8CoA + 7ADP + 7Pi + 14NADP+

20. Which lipoprotein transports dietary cholesterol and triglycerides to other parts of the body? a. VLDL b. HDL c. IDL

21. What is the overall energy yield (in molecules of ATP) from the oxidation of 1 molecule of Cerotic acid (C26:0) to acetyl-CoA (including beta-oxidation derived reduced coenzymes)? a. 450ATP b. 150ATP c. 178ATP

22. ATP at a high concentration acts as what type of inhibitor on phosphofructokinase? a. Substrate level phosphorylation b. Allosteric activator c. None of the above d. Allosteric inhibitor

23. What effect will insulin have on glycogen accumulation in the liver and muscles? a. It converts glycogen synthase from an inactive to an active form b. It promotes the activity of glycogen synthase c. It will inhibit glycogen accumulation d. It will promote glycogen accumulation

1. Which of the following statements about reaction rate is true? a. Reaction rates are independent from thermodynamic conditions (temperature) b. The presence of enzymes does not affect the rate of a reaction c. None of the above d. The reaction rate is the speed at which the reaction proceeds towards the state of equilibrium between substrate and product

2. Which of the following statements describes the action of an enzyme during enzymatic catalysis? a. The presence of an enzyme (E) alters the equilibrium from the substrate (S) to the product (P) b. The presence of an enzyme (E) decreases the transition state free energy in the reaction from substrate (S) to product (P) c. The presence of an enzyme (E) increases the transition free state energy in the reaction from substrate (S) to product (P) d. The presence of an enzyme (E) decreases the free energy difference between substrate (S) and product (P)

3. In what section of the human digestive tract does the main digestion of lipids take place? a. Stomach via pepsin b. Small intestine via pancreatic lipases c. Large intestine via peptidases d. Mouth via salivary amylase

4. During digestion, food passes through a number of organs that make up the digestive tract. What is the order in which food transits through the various organs? a. Mouth, stomach, oesophagus, small intestine, large intestine and rectum b. Mouth, oesophagus, stomach, large intestine, small intestine and rectum c. Mouth, stomach, oesophagus, large intestine, small intestine and rectum d. Mouth, oesophagus, stomach, small intestine, large intestine and rectum

5. What is the function of bile secreted by the pancreas with regard to the digestion of lipids? a. It has no role in the digestion of lipids b. It emulsifies fat droplets thus stopping them from aggregating c. It neutralises acidic chyme entering the duodenum d. It contains a number of carbohydrates

6. What have polysaccharides been catabolised into by the time they enter the small intestine? a. Polysaccharides b. Amino acids c. Monosaccharides d. Disaccharides

7. Which molecule reacts with oxaloacetate to form citrate and keep the TCA cycle moving? a. Malate b. Iso-citrate c. Acetyl-Co-A d. Pyruvate

8. The conversion of succinate to fumarate results in the reduction of what electron acceptor? a. NAD+ b. NADH c. FAD d. FADH2

9. The enzyme acetaldehyde dehydrogenase is an example of? a. A hydrolase b. A transferase c. A lyase d. An oxidoreductase

10. The digestion of protein in the small intestine is catalysed predominantly by which enzyme? a. Trypsin b. Ptyalin c. Pepsin d. Pepsinogen

11. The conversion of one molecule of glucose to two molecules of pyruvate results in the net formation of? a. 38 molecules of ATP b. 2 molecules of ATP c. 6 molecules of water d. 3 molecules of ATP

12. The reduction of pyruvate to lactate a. Reconverts NADH to NAD+ b. Provides more fuel to skeletal muscle than the conversion of glucose to pyruvate c. Occurs under aerobic conditions d. Produces 2 ATP

13. How many ATP molecules (or equivalents) does the conversion of pyruvate to form glucose consume? a. 2 b. 4 c. 6 d. 8

14. In the mitochondrial matrix are a. Glycogen molecules b. All the components of the electron transport chain c. The enzymes of the tricarboxylic acid cycle (Kreb’s cycle) d. The enzymes of gluconeogenesis

15. To control the flux through a pathway, the most effective regulation points are a. Reversible reactions b. Irreversible reactions c. Substrate-limited reactions d. Fastest reactions

16. In the electron transport chain, which donor results in the generation of the most ATP? a. FADH2 b. NADH c. ATP d. Carbon Dioxide

17. What cellular compartment becomes depleted of hydrogen ions during the mitochondrial electron transport? a. Mitochondrial matrix b. Ribosomes c. Mitochondrial inter-membrane space d. Cytosol

18. The passage of electrons from which enzyme complex in the electron transport chain is not accompanied by the pumping of protons into the intermembrane space? a. NADH dehydrogenase b. Succinate Co-Q reductase c. Cytochrome C oxidase d. Coenzyme Q-cytochrome C reductase

19. The formation of a molecule of ATP by ATP synthase from ADP and Pi by ATP synthase is an example of a. Conversion of mechanical energy into chemical energy b. Conversion of chemical energy into mechanical energy c. Conversion of potential energy into chemical energy d. None of the above

20. If the concentration of NADH is greater in the mitochondrial matrix than in the cytosol, how many ATP will arise from the oxidation of glyceraldehyde-3-phosphate in glycolysis per glucose molecule? a. 5 ATP b. 7 ATP c. 3 ATP d. 2 ATP

21. What two energy carrying molecules are produced by the light reactions of photosynthesis? a. NADPH and ATP b. NADPH and ADP c. NADP+ and ATP d. NADH and ATP

22. The light-independent reactions of photosynthesis take place in the a. Chloroplasts b. Thylakoid membranes c. Grannum d. Stroma

23. The Calvin cycle involves all of the following except a. The fixing of carbon b. Regeneration of NADP+ c. Reduction of Carbon d. The production of carbon dioxide in the form of waste

24. A compound which exerts allosteric control over an enzyme a. Is always the product of the reaction it affects b. Binds to a site remote from the active site c. Always inhibits the catalytic effect of the enzyme d. Binds to the active site of the enzyme thus inhibiting binding of the substrate

25. In glycolysis high levels of glucose-6-phosphate in a cell will inhibit which enzyme? a. Phosphofructokinase b. Fructose 1,6-biphosphtase c. Phosphorylase d. Hexokinase

26. In glycolysis what effect would high levels of acetyl-coA have on the catalytic activity of pyruvate kinase? a. No effect b. It would inhibit the activity of the enzyme c. It would promote the activity of the enzyme d. Pyruvate kinase is not involved in glycolysis

27. How does glucagon and epinephrine increase the production of glucose via gluconeogenesis? a. They have no effect on gluconeogenesis b. They inhibit the activity of fructose 2,6-biphosphatase c. They liberate glucose from glycogen stores d. They inhibit the activity of phosphofructokinase-2

28. In a fight or flight situation what effect does epinephrine have on the catalytic activity of glycogen phosphorylase? a. It is an allosteric promoter of the enzyme b. It stimulates the conversion of the enzyme into its active form thus increasing the formation of glycogen c. It inhibits the enzyme d. It stimulates the conversion of the enzyme into its active form thus increasing release of glucose from glycogen

29. What is the overall energy yield of beta-oxidation of palmitate? a. 108 ATP b. 96 ATP c. 80 ATP d. 28 ATP

30. The equation below represents the overall energy balance for the metabolism of which fatty acid? Palmitoyl-CoA + 7CoA + 7O2 + 28Pi + 28 ADP 8→Acetyl-CoA + 28 ATP + 7H2O a. Linoleic acid (C18:2) b. Palmitic acid (C16:0) c. Arachadonic acid (C20:4) d. Palmitoleic acid (C16:1)

31. What is the overall energy yield from the metabolism of stearic acid (C18:0) a. 28 ATP b. 42 ATP c. 108 ATP d. 122 ATP

32. Why are two additional enzymes required for the beta-oxidation of unsaturated fatty acids? a. The presence and configuration of the double bonds mean the fatty acid is no longer a substrate for the enzymes required for oxidation of a saturated fatty acid b. They contain trans double bonds c. They contain double bonds between the alpha and beta carbons d. No additional enzymes are require

33. What is the mechanism by which fatty acids enter mitochondrial matrix for beta-oxidation a. Carnithine shuttle b. Membrane diffusion c. Electron transport chain d. Transacyclase

34. When are ketone bodies formed in the liver? a. When glucose levels are low b. When there is excess of fatty acids in the blood c. When liver glycogen reserves are full d. When glucose is in plentiful supply

35. Brain cells can obtain energy from the oxidation of ketone bodies during starvation? a. True b. False

36. What effect will a high level of malonyl coA in the hepatocyte have on ketone body production? a. It will dampen down ketone body production b. It will increase ketone body production because there is more substrate available c. It will inhibit the action of carnithine palmitoyl coA d. No effect

37. Why would a low level of insulin production increase the production of ketone bodies a. Changes the insulin/glucagon ratio b. Insulin blocks lipolysis and therefore the substrate for ketone body production c. Insulin increases the production of malonyl CoA which in turn inhibits CPT1 thus dampening down ketogenesis d. Insulin blocks lipolysis and therefore the substrate for ketone body production

38. Where in the body are dietary fats emulsified into micelles? a. Stomach b. Duodenum c. Ileum d. Pancreas

39. Which lipoprotein has the function of removing cholesterol from plasma? a. HDL b. VLDL c. LDL d. Chylomicrons

40. Which of the following lipoproteins is the largest in size? a. IDLs b. Chylomicrons c. VLDLs d. LDLs

41. Which lipoprotein has the effect of transporting mainly endogenously produced triacylglycerols to the tissues from the liver? a. IDLs b. Chylomicrons c. VLDLs d. HDLs

42. Insulin has the effect of reducing plasma lipid concentration following a meal. Which of the following does it not do? a. Stimulates the release of CCK b. Stimulates lipoprotein lipase in adipose tissue c. Suppresses release of VLDL from liver d. Suppresses the intracellular lipolysis of stored TAG in adipose

43. How many common end products of AA catabolism can be identified? a. 2 b. 4 c. 8 d. 6

44. What is the main pathway for pyruvate produced during amino acid catabolism a. Glucogenesis b. TCA cycle c. Glycolysis d. Oxidation of acetyl CoA

45. Why can’t ketogenic AA’s enter gluconeogenesis a. They are converted to acetyl CoA during catabolism b. There are no enzymes to do this c. Their carbon skeletons are too long d. They cannot be converted to acetyl CoA

46. Which two amino acids are purely ketogenic? a. Phenylalanine and tyrosine b. Leucine and lysine c. Tryptophan and leucine d. Isoleucine and methionine

47. How many amino acids are glucogenic and ketogenic? a. 3 b. None c. 5 d. 6

48. How many different types of amino acids are found in naturally occurring proteins? a. 18 b. 27 c. 12 d. 21

49. Which part of an amino acid can be oxidised to produce energy a. The carbon skeleton b. The amino group c. The carboxyl group d. They cannot be used to generate energy

50. Which of the following AA’s cannot be synthesised from an intermediate of the TCA cycle a. Valine b. Arginine c. Glutamic acid d. Aspartic acid

51. Which is the correct sequence for the manufacture of a protein from DNA a. Transcription, elongation, termination, translation b. Transcription, translation, elongation, termination c. Translation, initiation, elongation, termination d. Transcription, initiation, elongation, termination

52. Which 2 amino acids have a role in the urea cycle but not as building blocks in protein synthesis? a. Aspartate and arginine b. Ornithine and citrulline c. Glutamate and glutamine d. Tryptophan and methionine

53. In the formation of urea from ammonia, all of the following are correct except? a. Fumarate was produced b. The process involves a net consumption of ATP c. Aspartate supplies one of the nitrogens in urea d. It is a cytosolic process

54. Tryptophan and phenylalanine are… a. One essential and one non-essential b. Conditionally essential c. Non-essential d. Essential

55. The reaction that converts pyruvate to alanine and oxaloacetate to aspartate is a a. Transamination b. Oxidation c. Reduction

56. Which hormones act on the receptors by entering the cell membrane? a. Steroid hormones b. Eicosanoids c. Peptide hormones d. Amino acid derivatives

57. Which of the following hormones is not a steroid? a. Cortisol b. Testosterone c. Thyroxine d. Estradiol

2. Which metabolic pathway produces more ATP? a) They produce the same number of ATP b) Aerobic glycolysis c) Anaerobic glycolysis

3. At the end of the glycolytic pathway, for every molecule of glucose (fructose) at the beginning, how many ATP are gained? a) 4 b) 3 c) 2 d) 8

4. The conversion of pyruvate to lactate is an example of a ____________ reaction and is catalysed by the enzyme _____________. a) Reduction, lactate reductase b) Phosphorylation, pyruvate phosphate c) Condensation, lactate aldolase d) Reduction, lactate dehydrogenase

5. Fructose 1, 6-bisphosphate is split in 2, creating what? a) 2 X 3C sugars b) 1 X 3C sugar with phosphate and 1 X 3C sugar without c) 2 X 3C sugars with phosphate

6. What shifts the equilibrium in favour of the formation of glyceraldehyde-3-phosphate over dihydroxyacetone phosphate in step 5 of glycolysis? a) The continuous removal of glyceraldehyde-3-phosphate in the next step of glycolysis b) The action of the enzyme which catalyses the reaction c) The formation of dihydroxyacetone is favoured d) None of the above

7. Gluconeogenesis has how many key differences from glycolysis? a) 1 b) 3 c) 4 d) 2

8. In gluconeogenesis, which compound donates a phosphate group to oxaloacetate to form phosphoenolpyruvate? a) ATP b) GTP c) UTP d) None of the above

9. The decarboxylation and phosphorylation of oxaloacetate to PEP produces what? a) ADP + CO2 b) GDP + CO2 c) GTP + CO2 d) ATP + CO2

10. After decarboxylation of oxaloacetate, the phosphorylation to PEP is achieved via what? a) A phosphate group from GTP b) A phosphate group from ATP c) Inorganic phosphate

11. Which tissue is the main site for gluconeogenesis? a) Liver b) Kidneys c) Muscle d) Brain

13. All of the bypass reactions used in gluconeogenesis… a) Require mitochondrial enzymes b) Require high-energy equivalents c) Involve the removal of phosphate groups d) Are irreversible

14. Which glucose molecule reacts with the non-reducing end of glycogen for elongation of the chain? a) Glucose-6-phosphate b) Glucose-1-phosphate c) UDP-glucose d) Any of the above

15. The formation of a glycogen granule occurs by the formation of what? a) Alpha-1, 6 linkages b) Alpha-1, 4 linkages c) A combination of alpha-1, 4 and alpha-1, 6 linkages d) Beta-1, 4 linkages

16. The process of adding 1 glucose to glycogen uses how many ATP? a) 6 b) 8 c) 2 d) 4

17. What is the main source of Acetyl-CoA for fatty acid synthesis? a) Glucose oxidation b) Citric acid cycle c) Pentose phosphate pathway d) Fatty acid beta oxidation

18. Which of the following equations could be used to represent the synthesis of palmitate? a) Acetyl-CoA + 7ATP + 14NADPH + 14H⁺ → Palmitate + 8 CoA + 7ADP + 7Pi + 14NADP⁺ + 6H2O b) Acetyl-CoA + 7 Malonyl-CoA + 14NADPH + 14H⁺ → Palmitate + 7CO2 + 8 CoA + 14NADP⁺ + 6H2O c) 7 Acetyl-CoA + 7CO2 + 7ATP → 7 Malonyl-CoA + 7ADP + 7Pi d) 7 Malonyl-CoA + 14NADPH + 14H⁺ → Palmitate + 7CO2 + 8 CoA + 14NADP⁺ + 6H2O

19. Which of the following fatty acids would you consider to be essential in humans? a) Linoleate C18 (Δ9,12) b) Oleate C18:1 (Δ9) c) Stearate C18:0 d) Palmiteolate C16:1 (Δ9)

20. The principal conveyor of carbon atoms required for the synthesis of fatty acid with an even number of carbons is… a) Glucose b) Acetyl-CoA c) Propionyl-CoA d) Pyruvate

21. What is the energetic cost of synthesising one molecule of palmitate? a) 12 ATP b) 8 ATP c) 1 ATP d) 16 ATP

23. The equation below represents the overall energy balance for the metabolism of which fatty acid? Palmitoyl-CoA + 7 CoA + 7O2 + 28 Pi + 28ADP → Acetyl-CoA + 28ATP +7H2O a) Palmitic acid (C16:0) b) Arachadonic acid (C20:4) c) Linoleic acid (C18:2) d) Palmitoleic acid (C16:1)

25. Which combination of conditions below would have the effect of promoting glycolysis in cells? a) Low levels of ATP, citrate and Acetyl-CoA b) High levels of ATP, citrate and Acetyl-CoA c) Low glucose-6-phosphate, high fructose-6-phosphate and low AMP d) None of the above

26. In the biosynthesis of aspartate, ________________ transfers an amino group from ______________ to oxaloacetate to form aspartate, and α-ketoglutarate transfers an amino group from glutamate to oxaloacetate to form aspartate and α-ketoglutarate. a) Aspartase, asparagine b) Aspartate aminotransferase, glutamate c) Aspartate synthase, glutamine d) None of the above

27. Which intermediate from the glycolytic pathway can serve as a precursor for serine synthesis? a) Pyruvate b) Glucose-6-phosphate c) 3-Phosphoglycerate d) Fructose 1, 6-bisphosphate

28. How do HDL lipoproteins decrease intracellular levels of cholesterol? a) By accumulating cholesterol from the blood b) By accumulating cholesterol from cell membrane c) By stimulating endocytosis of cholesterol by the liver d) They do not decrease intracellular cholesterol levels

29. What is often the first step in the catabolism of amino acids? a) Oxidation b) Reduction c) Decarboxylation d) Deamination

30. How many amino acids are converted to pyruvate as an end product following amino acid catabolism? a) 4 b) 6 c) 7 d) 5

31. In mammals, in what form is excess nitrogen than is required for biosynthesis excreted? a) Creatinine b) Ammonium c) Uric acid d) Urea

32. In the degradation of an amino acid, to which compound is the amino group transferred in transamination? a) Glutamate b) Glutamine c) α-ketoglutarate d) Urea

33. In glycolysis, inhibition of hexokinase by glucose-6-phosphate is an example of… a) Covalent modification b) Hormonal control c) Product inhibition d) None of the above

34. How does ATP inhibit the activity of phosphofructokinase? a) Covalent modification b) Denaturation of the enzyme c) Product inhibition d) Allosteric inhibition

35. What effect will a high level of Malonyl-CoA in the hepatocyte have on ketone body production? a) No effect b) It will increase ketone body production because there is more substrate available c) It will inhibit the action of carnitine palmitoyl-CoA d) It will dampen down ketone body production

36. Which of the following statements about free fatty acids is false? a) Fatty acids oxidation yields the maximum amount of ATP on a per gram basis b) Fatty acids are oxidised to Acetyl-CoA in the liver c) Fatty acids esterified into triacylglycerols in adipose tissue cells d) Fatty acids are converted to glucose in the liver

37. What is the first reaction necessary to initiate the synthesis of a new fatty acid? a) Condensation of 2 Acetyl-CoA molecules b) Carboxylation of one molecule of Acetyl-CoA to Malonyl-CoA c) Condensation of Acetyl-CoA and Malonyl-CoA d) Condensation of a free fatty acid with coenzyme A

38. What is produced after each cycle of β-oxidation of a fatty acid? a) 1 FAD, 1 NADH, 1 Acetyl-CoA b) 1 FADH2, 1 NADH, 1 Acetyl-CoA c) 1 FAD, 1 NAD⁺, and 2 CO2 molecules d) 1 FADH2, 1 NADH, 2 CO2 molecules

39. Which of the following is not an end product of amino acid catabolism? a) Acetyl-CoA b) Pyruvate c) Fumarate d) Succinate

40. In glycolysis, what effect would high levels of Acetyl-CoA have on the catalytic activity of pyruvate kinase? a) It would promote the activity of the enzyme b) No effect c) Pyruvate kinase is not involved in glycolysis d) It would inhibit the activity of the enzyme

41. Which of the following is not an essential amino acid? a) Valine b) Isoleucine c) Leucine d) Serine

42. If the catabolism of an amino acid yields fumarate, such amino acid is to be considered… a) Ketogenic b) Glucogenic c) Both d) No amino acid yields fumarate as a product of its metabolism

43. Which of the following pairs of amino acids contains a sulphur atom? a) Leucine and isoleucine b) Cysteine and methionine c) Tryptophan and phenylalanine d) All amino acids contain sulphur

44. Control of which enzyme is key to hormonal regulation of glucose metabolism? a) Hexokinase b) Phosphofructokinase c) Pyruvate carboxylase d) Fructose 2, 6-bisphosphate

46. Which reaction in the gluconeogenesis pathway occurs in the mitochondria and not in the cytosol? a) Fructose 1, 6-bisphosphate → fructose 6-phosphate b) Pyruvate → oxaloacetate c) Glucose-6-phosphate → glucose d) Oxaloacetate → PEP

47. How many ATP molecules (or equivalents) are used in the conversion of 2 molecules of pyruvate to one molecule of glucose? a) 4 b) 6 c) 8 d) 3

49. Amino acids, fatty acids and glucose are oxidised and enter the citric acid cycle as… a) Pyruvate b) Acetate c) Oxaloacetate d) Acetyl-CoA

50. The first reaction of the citric acid cycle, which generates citrate, is… a) A condensation reaction b) An oxidative decarboxylation reaction c) A dehydrogenation reaction d) A dehydration reaction

51. The role of mitochondria in the cell is that of the centre for… a) Oxidative metabolism and ATP production b) Biosynthesis of amino acids c) Glycolysis d) Biosynthesis of fatty acids

52. How many molecules of ATP are estimated to be generated by the oxidation of FADH2 through the electron transport chain? a) 2 b) 1 c) 1.5 d) 2.5

53. Photosynthetic organisms derive their carbon from… a) Hydrocarbons b) Carbon monoxide c) Methane d) Carbon dioxide

54. During photosynthesis in chloroplasts, O2 is produced from __________ via reactions associated with _____________. a) CO2, photosystem II b) CO2, Calvin cycle c) H2O, photosystem II d) H2O, photosystem I

55. What energy-rich organic compound is produced as a result of the Calvin cycle? a) CO2 b) Glyceraldehyde-3-phosphate c) H2O d) ATP

56. If the full oxidation of palmitate (C16) requires 7 rounds of β-oxidation and yields 8 molecules of Acetyl-CoA, how many rounds of β-oxidation will be required and how many molecules of Acetyl-CoA will be generated to fully oxidise stearate (C18)? a) 8, 8 b) 9, 9 c) 8, 9 d) 9, 8

57. What is the main source of Acetyl-CoA for fatty acid synthesis? a) Fatty acid β-oxidation b) Glucose oxidation c) Pentose phosphate pathway d) Amino acids’ carbon skeleton

58. The production of ketone bodies from Acetyl-CoA in the liver cells of a mammalian organism increases when… a) The individual has just consumed a meal b) The concentration of insulin in the blood increases c) The individual undergoes a period of starvation d) There is excess triacylglycerols in the blood

59. What purpose is served by chlorophyll and other accessory pigments in plants? a) Plant pigments absorb solar injury b) Chlorophyll provides electrons that will be used to produce ATP c) Chlorophyll contains the enzymes needed to produce carbohydrates d) Plant pigments are needed to absorb solar energy and provide electrons that will be used to produce ATP

60. If plants were only able to undergo the cyclic pathway, which of the following would not be true? a) Plants would not produce oxygen b) Carbohydrate could still be produced, but in much smaller quantities c) More NADPH would be produced during the cyclic electron pathway d) ATP production would decrease due to a smaller amount of H⁺ being available

61. If the Calvin cycle uses three molecules of CO2 to produce six molecules of glyceraldehyde-3-phosphate (G3P), but only one G3P molecule is used to form a carbohydrate molecule, what happens to the other carbons that were taken in? a) Any unused CO2 is released into the environment b) The other five G3P molecules are used to generate RuBP c) Any unused G3P molecule is converted and stored as starch d) The remaining five G3P molecules are used to reduce CO2

62. What are the products of photosynthesis? a) Water and carbon dioxide b) Water and oxygen c) Oxygen and carbohydrate d) Carbohydrate and water

63. What organisms are capable of photosynthesis? a) Plants only b) Plants and algae only c) Plants and some bacteria only d) Plants, algae and some bacteria

64. Which of these is not a major photosynthetic pigment in plants? a) Chlorophyll a b) Chlorophyll b c) Chlorophyll c d) Carotenoid pigments

65. Why are plants green? a) The absorb only green wavelengths of light b) They absorb only yellow and blue wavelengths of light c) They reflect nearly all wavelengths of light d) They reflect green wavelengths of light e) They reflect yellow and blue wavelengths of light

66. The term "chloroplast" is derived in part from the Greek root that means… a) Plant b) Light c) Green d) Photosynthetic e) Oxygen

67. To what does the term stroma refer? a) The double membrane of the chloroplast b) A flattened disc or sac in the chloroplast c) A stack of a thylakoid membrane structures d) The central fluid-filled space of the chloroplast e) The cytochrome system in the membranes of the thylakoids

68. To what does the term grana refer? a) The double membrane of the chloroplast b) A flattened disc or sac in the chloroplast c) A stack of thylakoid membrane structures d) The central fluid-filled space of the chloroplast e) The cytochrome system in the membranes of the thylakoids

69. The tern derived from the Greek root that means “bed” or “mattress” is… a) Stroma b) Chloro c) Grana d) Photo e) Thylakoid

70. The term derived from the Greek root that means “sack-like” is… a) Stroma b) Chloro c) Grana d) Photo e) Thylakoid

71. Which of these is most closely associated with the process of electron transport? a) The double membrane of the chloroplast b) A flattened disc or sac in the chloroplast c) A stack of thylakoid membrane structures d) The central fluid-filled space of the chloroplast e) The pigment complex in the membranes of the thylakoids

72. Which statement is not true about photosystems? a) Photosystem I passes electrons on to Photosystem II b) Each photosystem contains numerous pigment molecules that act as antennae to capture light c) Photosystem I contains a reaction centre molecule that loses electrons which are then replaced by electrons from water d) Electrons in the reaction centre molecule are excited by absorbed solar energy and are passed along to an acceptor molecule

73. Protons (H⁺) accumulate in the thylakoid space during electron transport between Photosystems I and II. The excess of protons in the thylakoid space… a) Enters the photorespiration pathway b) Converts NADP to NADPH and generates ATP in the process c) Is small enough to diffuse back out through the lipid bilayer d) Raises the pH of the space until the processes stop e) Moves from the thylakoid space to the stroma through an ATP synthase complex channel that generates ATP

74. Which statement is not true about the cyclic electron pathway? a) It produces ATP b) It involves Photosystem I c) It produces NADPH d) Electrons lost from Photosystem I eventually return to Photosystem I

75. Which statement is not true about the non-cyclic electron pathway? a) Electrons are boosted to higher energy level in Photosystem I b) Sunlight excites electrons in Photosystem II c) It produces ATP d) It produces NADPH e) It produces carbohydrates through carbon dioxide fixation

76. Which statement is not true about photosynthesis? a) In non-cyclic photophosphorylation, water is split and oxygen is released. b) Photosystem II makes non-cyclic photophosphorylation more efficient than does cyclic photophosphorylation c) The cyclic system is used when there is insufficient NADP⁺ present to absorb electrons in plant cells d) More carbohydrate is produced during cyclic photophosphorylation than during non-cyclic photophosphorylation

77. Which is most closely associated with the Calvin cycle? a) ATP production b) Oxygen production c) Carbon dioxide fixation d) Carbon dioxide production e) Removal of electrons from water for passage through an electron transport system

78. The end product of the Calvin cycle is… a) ATP b) Ribulose bisphosphate (RuBP) c) Glyceraldehyde-3-phosphate (G3P) d) PEP carboxylase (PEPcase) e) Carbon dioxide

79. The major enzyme that catalyses the reduction of carbon dioxide is called… a) Ribulose bisphosphate carboxylase (rubisco) b) Glyceraldehyde-3-phosphate (G3P) c) PEP carboxylase (PEPcase)

80. Most plant foods, such as wheat, oats and rice, are in the group of… a) CAM plants b) C3 plants c) C4 plants

81. Which statement is not true about C3 and C4 plants? a) C3 plants are more successful in mild climates than C4 plants b) C4 plants contain chloroplasts only in part of their mesophyll cells c) C3 plants fix CO2 in the mesophyll cells d) C3 plants make glucose in the bundle sheath cells e) The first CO2 fixation product in a C4 plant is oxaloacetate

82. Photorespiration is a form of… a) Fixation of carbon dioxide in C4 plants b) Fixation of carbon dioxide in C3 plants c) Release of carbon dioxide in C4 plants d) Release of carbon dioxide in C3 plants

83. Which would be a CAM plant? a) Cactus b) Corn c) Rice d) Wheat e) Oak tree

84. Carbon dioxide movement into a plant leaf involves all of the following, except… a) Stomata b) Diffusion c) Electron transport systems d) Air

85. Photosynthetic pigments… a) Absorb specific wavelengths of light in their absorption spectra b) Include chlorophyll a, b, and the carotenoids c) Have their absorption spectra analysed using a spectrophotometer d) All of the above

86. Oxygen production in photosynthesis involves all of the following, except… a) Photosystem I b) Photosystem II c) Splitting of water d) All of the above are associated with the process

87. The Calvin cycle requires all of the following except ________________ to occur. a) ATP and NADPH b) Carbon dioxide c) Light d) Ribulose bisphosphate

88. G3P is used by plants for all of the following except the formation of… a) Fatty acids b) Amino acids c) Oxygen d) Sucrose

89. C4 plants… a) Store carbon dioxide temporarily as oxaloacetate b) Are found in hot, dry climate c) Have a net photosynthetic rate 2-3X that of C3 plants d) All of the above

90. While C4 plants have carbon dioxide fixation carbon dioxide uptake separated by location within the plant, CAM plants… a) Have these processes separated by time b) Fix much greater amounts of carbon dioxide than C4 plants c) Are found in tropical regions where nutrients are abundant d) All of the above

91. During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be re-oxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the re-oxidation of NADH is… a) Dihydroxyacetone phosphate → glycerol-3-phosphate b) Glucose-6-phosphate → fructose-6-phosphate c) Iso-citrate → α-ketoglutarate d) Oxaloacetate → malate e) Pyruvate → Lactate

92. In glycolysis, fructose 1, 6-bisphosphate is converted to two products with a standard free-energy change (DG'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change (DG’) be negative, enabling the reaction to proceed to the right? a) If the concentrations of the two products are high relative to that of fructose 1, 6-bisphosphate. b) The reaction will not go to the right spontaneously under any conditions because the DG'° is positive. c) Under standard conditions, enough energy is released to drive the reaction to the right. d) When there is a high concentration of fructose 1, 6-bisphosphate relative to the concentration of products. e) When there is a high concentration of products relative to the concentration of fructose 1, 6-bisphosphate.

93. Which one of the following statements about gluconeogenesis is false? a) For starting materials, it can use carbon skeletons derived from certain amino acids. b) It consists entirely of the reactions of glycolysis, operating in the reverse direction. c) It employs the enzyme glucose-6-phosphatase. d) It is one of the ways that mammals maintain normal blood glucose levels between meals. e) It requires metabolic energy (ATP or GTP).

94. The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except… a) ATP synthesis b) Catalysis by phosphoglycerate kinase c) Oxidation of NADH to NAD⁺ d) The formation of 1, 3-bisphosphate e) Utilisation of Pi

95. Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate? a) ADP b) ATP c) FAD/FADH2 d) Glyceraldehyde-3-phosphate e) NAD⁺/NADH

96. Which of the following is not true of the reaction catalysed by the pyruvate dehydrogenase complex? a) Biotin participates in the decarboxylation b) Both NAD⁺ and a flavin nucleotide act as electron carriers c) The reaction occurs in the mitochondrial matrix d) The substrate is held by the lipoyl-lysine “swinging arm” e) Two different cofactors containing –SH groups participate

97. Which of the following is not required for the oxidative decarboxylation of pyruvate to form Acetyl-CoA? a) ATP b) CoA-SH c) FAD d) Lipoic acid e) NAD⁺

98. The anaerobic conversion of 1mol of glucose to 2mol of lactate by fermentation is accompanied by a net gain of… a) 1mol of ATP b) 1mol of NADH c) 2mol of ATP d) 2mol of NADH e) None of the above

99. Which of the following is a cofactor in the reaction catalysed by glyceraldehyde-3-phosphate dehydrogenase? a) ATP b) Cu2+ c) Haem d) NAD⁺ e) NADP⁺

100. The conversion of 1mol of fructose 1, 6-bisphosphate to 2mol of pyruvate by the glycolytic pathway results in a net formation of… a) 1 mol of NAD⁺ and 2 mol of ATP b) 1 mol of NADH and 1 mol of ATP c) 2 mol of NAD⁺ and 4 mol of ATP d) 2 mol of NADH and 2 mol of ATP e) 2 mol of NADH and 4 mol of ATP

101. Which of the following statements is incorrect? a) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle b) In anaerobic muscle, pyruvate is converted to lactate c) In yeast growing anaerobically, pyruvate is converted to ethanol d) Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis e) Under anaerobic conditions pyruvate does not form because glycolysis does not occur

102. All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are also involved in the reversal of this flow (gluconeogenesis) except… a) Phosphoglycerate kinase b) Aldolase c) Enolase d) Phosphofructokinase-1 e) None of the above

103. Glycogen is converted to monosaccharide units by… a) Glucokinase b) Glucose-6-phosphatase c) Glycogen phosphorylase d) Glycogen synthase e) Glycogenase

104. All of the bypass reactions used in gluconeogenesis… a) Require high-energy equivalents b) Involve the removal of phosphate groups c) Are irreversible d) Require mitochondrial enzymes e) Are reversible

105. Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is correct? a) One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate b) The methyl (—CH3) group is eliminated as CO c) The process occurs in the cytosolic compartment of the cell d) The pyruvate dehydrogenase complex uses all of the following as cofactors: ATP, NAD⁺, lipoic acid, pyridoxal phosphate (PLP), and FAD e) The reaction is so important to energy production that pyruvate dehydrogenase operates at full speed under all conditions.

106. Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds would you expect to decrease in concentration? a) Citrate b) Fumarate c) Iso-citrate d) Pyruvate e) Succinate

107. Which of the following is not an intermediate of the citric acid cycle? a) Acetyl-CoA b) Citrate c) Oxaloacetate d) Succinyl-CoA e) α-ketoglutarate

108. Oxaloacetate uniformly labelled with C (i.e., with equal amounts of C in each of its carbon atoms) is condensed with unlabelled acetyl-CoA. After a single pass through the citric acid cycle back to oxaloacetate, what fraction of the original radioactivity will be found in the oxaloacetate? a) all b) 1/2 c) 1/3 d) 1/4 e) 3/4

109. The reaction of the citric acid cycle that is most similar to the pyruvate dehydrogenase complex-catalysed conversion of pyruvate to Acetyl-CoA is the conversion of… a) Citrate to iso-citrate b) Fumarate to malate c) Malate to oxaloacetate d) Succinyl-CoA to succinate e) α-ketoglutarate to Succinyl-CoA

110. Which of the following is not true of the citric acid cycle? a) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane b) In the presence of malonate, one would expect succinate to accumulate c) Oxaloacetate is used as a substrate but is not consumed in the cycle d) Succinate dehydrogenase channels electrons directly into the electron transfer chain e) The condensing enzyme is subject to allosteric regulation by ATP and NADH

111. Conversion of 1mol of Acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of… a) 1mol of citrate b) 1mol of FADH2 c) 1mol of NADH d) 1mol of oxaloacetate e) 7mol of ATP

112. The oxidative decarboxylation of α-ketoglutarate proceeds by means of multistep reactions in which all but one of the following cofactors are required. Which one is not required? a) ATP b) Coenzyme A c) Lipoic acid d) NAD⁺ e) Thiamine pyrophosphate

113. The conversion of 1mol of pyruvate to 3mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields ______ mol of NADH, _____ mol of FADH2, and _____ mol of ATP (or GTP). a) 2, 2, 2 b) 3, 1, 1 c) 3, 2, 0 d) 4, 1, 1 e) 4, 2, 1

114. For every molecule of glucose, how many molecules of CO2 are released in the citric acid cycle? a) 1 b) 2 c) 4 d) 5 e) 6

115. Almost all of the oxygen (O2) one consumes in breathing is converted to… a) Acetyl-CoA b) Carbon dioxide (CO2) c) Carbon monoxide, and then to carbon dioxide d) Water e) None of the above

116. Antimycin A blocks electron transfer between cytochromes b and c1. If intact mitochondria were incubated with antimycin A, excess NADH, and an adequate supply of O2, which of the following would be found in the oxidized state? a) Coenzyme Q b) Cytochrome a3 c) Cytochrome b d) Cytochrome e e) Cytochrome f

117. In the reoxidation of QH2 by purified ubiquinone-cytochrome c reductase (Complex III) from heart muscle, the overall stoichiometry of the reaction requires 2mol of cytochrome c per mole of QH2 because… a) Cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor b) Cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor c) Cytochrome c is water soluble and operates between the inner and outer mitochondrial membranes d) Heart muscle has a high rate of oxidative metabolism, and therefore requires twice as much cytochrome c as QH2 for electron transfer to proceed normally e) Two molecules of cytochrome c must first combine physically before they are catalytically active

118. 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

119. During oxidative phosphorylation, the proton motive force that is 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

120. The rate of oxidative phosphorylation in mitochondria is controlled primarily by… a) Feedback inhibition by CO₂ b) The availability of NADH from the TCA cycle c) The concentration of citrate (or) the glycerol-3-phosphate shuttle d) The mass-action ratio of the ATD-ADP system e) The presence of thermogenin

121. The compound that consists of ribose linked by an N-glycosidic bond to N-9 of adenine is… a) A deoxyribonucleoside b) A purine nucleotide c) A pyrimidine nucleotide d) Adenosine monophosphate e) Adenosine

122. The difference between a ribonucleotide and a deoxyribonucleotide is… a) A deoxyribonucleotide has an —H instead of an —OH at C-2 b) A deoxyribonucleotide has α configuration; ribonucleotide has the β configuration at C-1 c) A ribonucleotide has an extra —OH at C-4 d) A ribonucleotide has more structural flexibility than deoxyribonucleotide e) A ribonucleotide is a pyranose, deoxyribonucleotide is a furanose

123. The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA… a) Always link A with T and G with C b) Are susceptible to alkaline hydrolysis c) Are uncharged at neutral pH d) Form between the planar rings of adjacent bases e) Join the 3' hydroxyl of one nucleotide to the 5' hydroxyl of the next

124. The alkaline hydrolysis of RNA does not produce… a) 2'-AMP b) 2', 3'-cGMP c) 2'-CMP d) 3', 5'-cAMP e) 3'-UMP

Biochemistry MCQs Flashcards

(212 cards)