Harper’s Illustrated Biochemistry, 29th Edition (2012)
SECTION II. Bioenergetics & the Metabolism of Carbohydrates & Lipids
Exam Questions
Section II
1. A number of compounds inhibit oxidative phosphorylation—the synthesis of ATP from ADP and inorganic phosphate linked to oxidation of substrates in mitochondria. Which of the following describes the action of oligomycin?
A. It discharges the proton gradient across the mitochondrial inner membrane.
B. It discharges the proton gradient across the mitochondrial outer membrane.
C. It inhibits the electron transport chain directly by binding to one of the electron carriers in the mitochondrial inner membrane.
D. It inhibits the transport of ADP into, and ATP out of, the mitochondrial matrix.
E. It inhibits the transport of protons back into the mitochondrial matrix through the stalk of the primary particle.
2. A number of compounds inhibit oxidative phosphorylation—the synthesis of ATP from ADP and inorganic phosphate linked to oxidation of substrates in mitochondria. Which of the following describes the action of an uncoupler?
A. It discharges the proton gradient across the mitochondrial inner membrane.
B. It discharges the proton gradient across the mitochondrial outer membrane.
C. It inhibits the electron transport chain directly by binding to one of the electron carriers in the mitochondrial inner membrane.
D. It inhibits the transport of ADP into, and ATP out of, the mitochondrial matrix.
E. It inhibits the transport of protons back into the mitochondrial matrix through the stalk of the primary particle.
3. A student takes some tablets she is offered at a disco, and without asking what they are she swallows them. A short time later she starts to hyperventilate, and becomes very hot. What is the most likely action of the tablets she has taken?
A. An inhibitor of mitochondrial ATP synthesis.
B. An inhibitor of mitochondrial electron transport.
C. An inhibitor of the transport of ADP into mitochondria to be phosphorylated.
D. An inhibitor of the transport of ATP out of mitochondria into the cytosol.
E. An uncoupler of mitochondrial electron transport and oxidative phosphorylation.
4. AA eats a very poor diet and consumes two bottles of vodka a day. He is admitted to a hospital in coma. He is hyperventilating and has low blood pressure and high cardiac output. A chest x-ray shows that his heart is enlarged. Laboratory tests show that he is suffering from thiamin (vitamin B1) deficiency. Which of the following enzymes is most likely to be affected?
A. Lactate dehydrogenase
B. Pyruvate carboxylase
C. Pyruvate decarboxylase
D. Pyruvate dehydrogenase
E. Pyruvate kinase
5. In monitoring glycemic control in diabetic patients, urine or blood glucose can be measured in two ways: chemically, using an alkaline copper reagent that detects reducing compounds; and biochemically, using the enzyme glucose oxidase. In a series of experiments both methods were used on the same urine sample and the result was positive for the alkaline copper reagent and negative using glucose oxidase. Which of the following is the most likely diagnosis for the person being tested?
A. A diabetic with good glycemic control.
B. A diabetic with poor glycemic control.
C. A normal healthy person who has fasted overnight.
D. A normal healthy person who has just eaten a meal.
E. A healthy person who has essential pentosuria.
6. A 25-year-old man undertakes a prolonged fast for religious reasons. Which of the following metabolites will be elevated in his blood plasma after 24 hours?
A. Glucose
B. Glycogen
C. Ketone bodies
D. Non-esterified fatty acids
E. Triacylglycerol
7. A 25-year-old man undertakes a prolonged fast for religious reasons. Which of the following metabolites will be most elevated in his blood plasma after 3 days?
A. Glucose
B. Glycogen
C. Ketone bodies
D. Non-esterified fatty acids
E. Triacylglycerol
8. A 25-year-old man visits his GP complaining of abdominal cramps and diarrhea after drinking milk. What is the most likely cause of his problem?
A. Bacterial and yeast overgrowth in the large intestine.
B. Infection with the intestinal parasite Giardia lamblia.
C. Lack of pancreatic amylase.
D. Lack of small intestinal lactase.
E. Lack of small intestinal sucrase-isomaltase.
9. Which one of following statements about favism (lack of glucose 6-phosphate dehydrogenase) and the pentose phosphate pathway is CORRECT?
A. In favism red blood cells are more susceptible to oxidative stress because of a lack of NADPH for fatty acid synthesis.
B. People who lack glucose 6-phosphate dehydrogenase cannot synthesize fatty acids because of a lack of NADPH in liver and adipose tissue.
C. The pentose phosphate pathway is especially important in tissues that are synthesizing fatty acids.
D. The pentose phosphate pathway is the only source of NADPH for fatty acid synthesis.
E. The pentose phosphate pathway provides an alternative to glycolysis only in the fasting state.
10. Which one of following statements about glycogen synthesis and utilization is CORRECT?
A. Glycogen is synthesized in the liver in the fed state, then exported to other tissues in low-density lipoproteins.
B. Glycogen reserves in liver and muscle will meet energy requirements for several days in prolonged fasting.
C. Liver synthesizes more glycogen when the hepatic portal blood concentration of glucose is high because of the activity of glucokinase in the liver.
D. Muscle synthesises glycogen in the fed state because glycogen phosphorylase is activated in response to insulin.
E. The plasma concentration of glycogen increases in the fed state.
11. In glycolysis, the conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate results in the formation of
A. 1 mol NAD+ and 2 mol of ATP.
B. 1 mol NADH and 1 mol of ATP.
C. 2 mol NAD+ and 4 mol of ATP.
D. 2 mol NADH and 2 mol of ATP.
E. 2 mol NADH and 4 mol of ATP.
12. Which one of the following statements about fatty acid metabolism is CORRECT?
A. Acylcarnitine is formed from acyl-CoA and carnitine at the inner face of the inner mitochondrial membrane.
B. Acyl-CoA can only cross the inner mitochondrial membrane in exchange for free CoA leaving the mitochondrial matrix.
C. Creatinine is essential for transport of fatty acids into the mitochondrial matrix.
D. In the fed state, the main source of fatty acids for tissues is triacylglycerol in chylomicrons and very low-density lipoproteins (VLDL).
E. β-Oxidation of fatty acids occurs in the cytosol.
13. Which one of the following statements about synthesis of fats is CORRECT?
A. Synthesis of triacylglycerol in adipose tissue can only occur when gluconeogenesis is occurring.
B. Synthesis of triacylglycerol in adipose tissue is stimulated when the insulin/glucagon ratio is low.
C. Synthesis of triacylglycerol in the liver can only occur when glycolysis is active.
D. Triacylglycerol is synthesized from glycerol 3-phosphate and acyl CoA in adipose tissue.
E. Triacylglycerol is synthesized from monoacylglycerol and acyl CoA in adipose tissue.
14. Which of the plasma lipoproteins is best described as follows: synthesized in the intestinal mucosa, containing a high concentration of triacylglycerol and mainly cleared from the circulation by adipose tissue and muscle?
A. Chylomicrons
B. High-density lipoprotein
C. Intermediate density lipoprotein
D. Low-density lipoprotein
E. Very low-density lipoprotein
15. Which of the plasma lipoproteins is best described as follows: synthesized in the liver, containing a high concentration of triacylglycerol and mainly cleared from the circulation by adipose tissue and muscle?
A. Chylomicrons
B. High-density lipoprotein
C. Intermediate density lipoprotein
D. Low-density lipoprotein
E. Very low-density lipoprotein
16. Which of the plasma lipoproteins is best described as follows: formed in the circulation by removal of triacylglycerol from very low-density lipoprotein, and containing cholesterol taken up from high-density lipoprotein, cleared by the liver?
A. Chylomicrons
B. High-density lipoprotein
C. Intermediate density lipoprotein
D. Low-density lip oprotein
E. Very low-density lipoprotein
17. Which of the following will be elevated in the bloodstream about 2 hours after eating a high-fat meal?
A. Chylomicrons
B. High-density lipoprotein
C. Ketone bodies
D. Non-esterified fatty acids
E. Very low-density lipoprotein
18. Which of the following will be elevated in the bloodstream about 4 hours after eating a high-fat meal?
A. Chylomicrons
B. High-density lipoprotein
C. Ketone bodies
D. Non-esterified fatty acids
E. Very low-density lipoprotein
19. After they are produced from acetyl-CoA in the liver, ketone bodies are mainly used for which one of the following processes?
A. Excretion as waste products.
B. Energy generation in the liver.
C. Conversion to fatty acids for storage of energy.
D. Generation of energy in the tissues.
E. Generation of energy in red blood cells.
20. Which one of the following statements concerning the biosynthesis of cholesterol is CORRECT?
A. The rate-limiting step is the formation of 3-hydroxy 3-methylglutaryl-CoA (HMG-CoA) by the enzyme HMG-CoA synthase.
B. Synthesis occurs in the cytosol of the cell.
C. All the carbon atoms in the cholesterol synthesized originate from acetyl-CoA.
D. Squalene is the first cyclic intermediate in the pathway.
E. The initial substrate is mevalonate.
21. The class of drugs called statins have proved very effective against hypercholesterolemia, a major cause of atherosclerosis and associated cardiovascular disease. These drugs reduce plasma cholesterol levels by:
A. Preventing absorption of cholesterol from the intestine.
B. Increasing the excretion of cholesterol from the body via conversion to bile acids.
C. Inhibiting the conversion of 3-hydroxy-3-methylglutaryl-CoA to mevalonate in the pathway for cholesterol biosynthesis.
D. Increasing the rate of degradation of 3-hydroxy-3-methylglutaryl CoA reductase.
E. Stimulating the activity of the LDL receptor in the liver.
22. Which one of the following statements about the free energy change (ΔG) in a biochemical reaction is CORRECT?
A. If ΔG is negative, the reaction proceeds spontaneously with a loss of free energy.
B. In an exergonic reaction, ΔG is positive.
C. The standard free energy change when reactants are present in concentrations of 1.0 mol/L and the pH is 7.0 is represented as ΔG0
D. In an endergonic reaction, ΔG is negative.
E. If ΔG is 0, the reaction is essentially irreversible.
23. Which one of the following statements about the citric acid cycle is CORRECT?
A. It produces most of the ATP in anaerobic organisms.
B. It oxidizes acetyl-CoA derived from fatty acid oxidation.
C. It provides acetyl-CoA for the synthesis fatty acids.
D. It slows down when energy levels are low.
E. It provides ATP mainly by substrate-linked phosphorylation.
24. Which one of the following is the major product of fatty acid synthase?
A. Acetyl-CoA
B. Oleate
C. Palmitoyl-CoA
D. Acetoacetate
E. Palmitate
25. Which one of the following statements concerning chylomicrons is CORRECT?
A. Chylomicrons are made inside intestinal cells and secreted into lymph, where they acquire apolipoproteins B and C.
B. The core of chylomicrons contains triacylglycerol and phospholipids.
C. The enzyme hormone sensitive lipase acts on chylomicrons to release fatty acids from triacylglycerol when they are bound to the surface of endothelial cells in blood capillaries.
D. Chylomicron remnants differ from chylomicrons in that they are smaller and contain a lower proportion of triacylglycerol.
E. Chylomicrons are taken up by the liver.
26. For each turn of the citric acid cycle, 3NADH and 1 FADH2 molecules are formed and oxidized via the respiratory chain producing:
A. 10 ATP molecules
B. 4 ATP molecules
C. 9 ATP molecules
D. 7 ATP molecules
E. 12 ATP molecules
27. The subcellular site of the breakdown of long chain fatty acids to acetyl-CoA via β-oxidation is:
A. The cytosol
B. The matrix of the mitochondria
C. The endoplasmic reticulum
D. The mitochondrial intermembrane space
E. The Golgi apparatus
28. Which one of the following statements concerning fatty acid molecules is CORRECT?
A. They consist of a carboxylic acid head group attached to a carbohydrate chain.
B. They are called polyunsaturated when they contain one or more carbon-carbon double bonds.
C. Their melting points increase with increasing unsaturation.
D. They almost always have their double bonds in the cis configuration when they occur naturally.
E. They occur in the body mainly in the form of free (non-esterified) fatty acids.
29. The flow of electrons through the respiratory chain and the production of ATP are normally tightly coupled. The processes are uncoupled by which of the following:
A. Cyanide
B. Oligomycin
C. Thermogenin
D. Carbon monoxide
E. Hydrogen sulphide