General, Organic & Biological Chemistry, 5e (Timberlake)
Chapter 24 Metabolic Pathways for Lipids and Amino Acids
24.1 Multiple-Choice Questions
1) The digestion of fats begins in the
A) mouth.
B) stomach.
C) small intestine.
D) large intestine.
E) pancreas.
Answer: C
Objective: 24.1
Global Outcomes: GO2
2) The digestion of fats begins when the fat globules are
A) emulsified by bile salts.
B) attacked by protease enzymes to form smaller fat globules.
C) converted to lipoproteins for greater solubility.
D) hydrolyzed to glucose and amino acids.
E) hydrolyzed to glycerol and fatty acids.
Answer: A
Objective: 24.1
Global Outcomes: GO2
3) Fatty acids and glycerol are produced from the metabolism of
A) lipids.
B) proteins.
C) carbohydrates.
D) amino acids.
E) glucose.
Answer: A
Objective: 24.1
Global Outcomes: GO2
4) Most of the energy stored in the human body is in the form of
A) glycogen.
B) glucose.
C) muscle tissue.
D) triacylglycerols.
E) the amino acid pool.
Answer: D
Objective: 24.1
Global Outcomes: GO2
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5) Fat cells are known as
A) lysosomes.
B) adipocytes.
C) glycerides.
D) islet cells.
E) monoacylglycerols.
Answer: B
Objective: 24.1
Global Outcomes: GO2
6) The small droplets of fat that are the first step in the digestion of dietary fats are called
A) emulsions.
B) detergents.
C) bile drops.
D) lipoproteins.
E) micelles.
Answer: E
Objective: 24.1
Global Outcomes: GO2
7) The action of pancreatic lipase on triacylglycerols produces
A) emulsions.
B) micelles.
C) monoacylglycerols and free fatty acids.
D) high-density lipoproteins.
E) low-density lipoproteins.
Answer: C
Objective: 24.1
Global Outcomes: GO2
8) A chylomicron is a
A) lipase.
B) digestive enzyme.
C) triacylglycerol.
D) transport lipoprotein.
E) storage protein.
Answer: D
Objective: 24.1
Global Outcomes: GO2
9) Fatty acids are not a source of energy for the brain because
A) they cannot diffuse across the blood-brain barrier.
B) the citric acid cycle does not operate in the brain.
C) chylomicrons are too large for absorption by brain cells.
D) they are metabolized before they get as far as the brain.
E) there is no lipase in the brain.
Answer: A
Objective: 24.1
Global Outcomes: GO2
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10) The source of energy for red blood cells is
A) amino acids.
B) fatty acids.
C) glycerol.
D) glucose.
E) lactate.
Answer: D
Objective: 24.1
Global Outcomes: GO2
11) The heart muscle's primary source of fuel is
A) glucose.
B) fatty acids.
C) amino acids.
D) glycogen.
E) lactate.
Answer: B
Objective: 24.1
Global Outcomes: GO2
12) Red blood cells do not metabolize fatty acids because they have
A) no nucleus.
B) a cell wall.
C) a cell membrane.
D) no mitochondria.
E) no DNA.
Answer: D
Objective: 24.1
Global Outcomes: GO2
13) Fat stores in the body are mobilized when
A) adipocyte concentrations are high.
B) blood glucose levels are high.
C) glucagon production is low.
D) insulin production is high.
E) glucose and glycogen stores are low.
Answer: E
Objective: 24.1
Global Outcomes: GO2
14) The enzymes that break down triacylglycerols into fatty acids and glycerol are called
A) lyases.
B) aconitases.
C) lipases.
D) hydrolases.
E) oxidoreductases.
Answer: C
Objective: 24.1
Global Outcomes: GO2
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15) Most of the glycerol produced by fatty acid breakdown goes to the
A) pancreas.
B) gall bladder.
C) liver.
D) small intestine.
E) brain.
Answer: C
Objective: 24.1
Global Outcomes: GO2
16) Most of the glycerol produced by fatty acid breakdown is converted eventually to
A) glucose.
B) protein.
C) fat.
D) lactate.
E) amino acids.
Answer: A
Objective: 24.1
Global Outcomes: GO2
17) The removal of 2-carbon segments of a fatty acid for further metabolism is called
A) β oxidation.
B) transamination.
C) deglyceration.
D) dehydration.
E) decarboxylation.
Answer: A
Objective: 24.2
Global Outcomes: GO2
18) The 2-carbon segments removed from a fatty acid during metabolism are used to form
A) glucose.
B) pyruvate.
C) lactate.
D) CoA.
E) acetyl CoA.
Answer: E
Objective: 24.2
Global Outcomes: GO2
19) The series of reactions that produces energy by hydrolyzing fats to units of acetyl CoA is called
A) transamination.
B) β oxidation.
C) hydration.
D) hydrolysis.
E) β reduction.
Answer: B
Objective: 24.2
Global Outcomes: GO2
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20) Which step is found in the breakdown of a fat?
A) an activation that requires 1 ATP
B) an oxidation with a cytochrome
C) an oxidation with CoQ
D) direct substrate phosphorylation
E) production of pyruvate
Answer: A
Objective: 24.2
Global Outcomes: GO2
21) During complete oxidation of the fatty acid CH3(CH2)18COOH, ________ molecules of acetyl CoA
are produced, and the fatty acid goes through the β-oxidation cycle ________ times.
A) ten; ten
B) nine; ten
C) nine; nine
D) nine; eight
E) ten; nine
Answer: E
Objective: 24.2
Global Outcomes: GO4
22) In the activation of a fatty acid, energy from the hydrolysis of ATP is used to
A) form a double bond in an oxidation reaction.
B) join the fatty acid to CoA.
C) add a molecule of water across a double bond to give a hydroxyl group on the β carbon.
D) oxidize the hydroxyl group on the β carbon.
E) cause a unit of acetyl CoA to separate from the fatty acid chain.
Answer: B
Objective: 24.2
Global Outcomes: GO2
23) The 2-carbon units obtained by degradation of a fatty acid are further metabolized in
A) gluconeogenesis.
B) the citric acid cycle.
C) β oxidation.
D) glycolysis.
E) transamination.
Answer: B
Objective: 24.2
Global Outcomes: GO2
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24) The function of fatty acyl CoA is to
A) activate a fatty acid for metabolism.
B) produce a 2-carbon segment for metabolism.
C) isomerize cis fatty acids.
D) cross the blood-brain barrier.
E) produce a lipoprotein.
Answer: A
Objective: 24.2
Global Outcomes: GO2
25) Fatty acyl CoA cannot cross into the mitochondrial matrix until
A) it is cut into 2-carbon segments.
B) the citric acid cycle has begun.
C) β oxidation has taken place.
D) the mitochondrial membrane undergoes a modification.
E) it binds with a charged carrier molecule called carnitine.
Answer: E
Objective: 24.2
Global Outcomes: GO2
26) Beta-oxidation takes place in the
A) nucleus.
B) cytosol.
C) cytoplasm.
D) mitochondrial matrix.
E) Golgi body.
Answer: D
Objective: 24.2
Global Outcomes: GO2
27) What is the total number of ATP molecules produced from the lauric acid (C 12H24O2) found in
coconut oil?
A) 78 ATP
B) 90 ATP
C) 100 ATP
D) 97 ATP
E) 95 ATP
Answer: A
Objective: 24.3
Global Outcomes: GO4
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28) The complete oxidation of CH3(CH2)8COOH produces ________ molecules of ATP.
A) 80
B) 78
C) 82
D) 64
E) 76
Answer: D
Objective: 24.3
Global Outcomes: GO4
29) Myristic acid, a C14 fatty acid, produces ________ acetyl CoA when completely metabolized.
A) 2
B) 5
C) 7
D) 12
E) 14
Answer: C
Objective: 23.3
Global Outcomes: GO4
30) Myristic acid, a C14 fatty acid, undergoes the β-oxidation cycle ________ times.
A) 2
B) 4
C) 6
D) 7
E) 14
Answer: C
Objective: 23.3
Global Outcomes: GO4
31) The energy released by the β oxidation of a cis fatty acid is
A) slightly more than that obtained from a trans fatty acid.
B) slightly less than that obtained from a trans fatty acid.
C) the same as that obtained from a trans fatty acid.
D) less than that obtained from one glucose molecule.
E) used immediately to form ATP.
Answer: B
Objective: 23.3
Global Outcomes: GO2
32) Fats are higher in caloric value than carbohydrates because
A) 1 gram of fat produces significantly more ATP than 1 gram of glucose.
B) fats can make use of the citric acid cycle.
C) fats make use of β oxidation.
D) 1 gram of glucose weighs more than 1 gram of fat.
E) 1 gram of glucose contains more moles than 1 gram of fat.
Answer: A
Objective: 24.3
Global Outcomes: GO2
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33) Leptin is
A) a digestive enzyme.
B) a cofactor for fatty acid oxidation.
C) an obesity gene.
D) a zymogen.
E) a hormone stored in fat cells.
Answer: E
Objective: 24.3
Global Outcomes: GO2
34) Each acetyl CoA produces ________ ATP in the citric acid cycle.
A) 2
B) 6
C) 10
D) 12
E) 24
Answer: C
Objective: 24.3
Global Outcomes: GO4
35) When excess acetyl CoA accumulates in the liver, a pathway called ________ is initiated.
A) transamination
B) glycolysis
C) gluconeogenesis
D) emulsification
E) ketogenesis
Answer: E
Objective: 24.4
Global Outcomes: GO2
36) Ketosis is a condition that can occur if
A) ketone bodies cannot be completely metabolized.
B) too many ketones are ingested.
C) too much protein is available in the diet.
D) the brain is starved of glucose.
E) low fat intake occurs.
Answer: A
Objective: 24.4
Global Outcomes: GO2
37) In Type II diabetes mellitus,
A) blood glucose levels are too low.
B) glucose intake is too low.
C) birth of a baby restores normal pancreatic function.
D) sufficient insulin is produced, but cannot be used.
E) the pancreas produces insufficient insulin.
Answer: D
Objective: 24.4
Global Outcomes: GO2
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38) Ketosis can lower the blood pH below 7.4, producing the condition
A) anemia.
B) hyponatremia.
C) hypokalemia.
D) acidosis.
E) alkalosis.
Answer: D
Objective: 24.4
Global Outcomes: GO2
39) In Type I diabetes mellitus,
A) blood glucose levels are too low.
B) glucose intake is too low.
C) birth of a baby restores normal pancreatic function.
D) sufficient insulin is produced, but cannot be used.
E) the pancreas produces insufficient insulin.
Answer: E
Objective: 24.4
Global Outcomes: GO2
40) Malonyl CoA contains a 3-carbon compound used in
A) lipogenesis.
B) acetyl CoA formation.
C) gluconeogenesis.
D) glycogenolysis.
E) the citric acid cycle.
Answer: A
Objective: 24.5
Global Outcomes: GO2
41) The letters ACP stand for
A) acetyl Coenzyme P.
B) aconitate protein complex.
C) acetyl condensing protein.
D) acyl carrier protein.
E) acetyl CoA-palmitate.
Answer: D
Objective: 24.5
Global Outcomes: GO2
42) Fatty acid synthesis takes place primarily in
A) liver cells.
B) intestinal cells.
C) brain cells.
D) muscle cells.
E) adipocytes.
Answer: E
Objective: 24.5
Global Outcomes: GO2
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43) The production of new fatty acids is called
A) gluconeogenesis.
B) β oxidation.
C) transesterification.
D) oxidation.
E) lipogenesis.
Answer: E
Objective: 24.5
Global Outcomes: GO2
44) Acyl carrier protein is used in
A) β oxidation.
B) lipogenesis.
C) gluconeogenesis.
D) acetyl CoA production.
E) fatty acid degradation.
Answer: B
Objective: 24.5
Global Outcomes: GO2
45) The coenzyme(s) used in fatty acid synthesis is (are)
A) NADH.
B) FADH2.
C) NADPH.
D) NADH and NADPH.
E) FADH2 and NADH.
Answer: C
Objective: 24.5
Global Outcomes: GO2
46) The digestion of protein begins in the
A) mouth.
B) stomach.
C) small intestine.
D) large intestine.
E) pancreas.
Answer: B
Objective: 24.6
Global Outcomes: GO2
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47) The initial digestion of protein is catalyzed by an enzyme called
A) chymotrypsin.
B) peptidase.
C) pepsin.
D) amylase.
E) trypsin.
Answer: C
Objective: 24.6
Global Outcomes: GO2
48) In a(n) ________ reaction, NH4+is produced when glutamate is converted to α-ketoglutarate.
A) dehydrogenation
B) transamination
C) oxidative deamination
D) reduction
E) hydration
Answer: C
Objective: 24.6
Global Outcomes: GO2
49) The nitrogen for nucleotide synthesis comes from
A) carbohydrates.
B) fats.
C) proteins.
D) DNA.
E) RNA.
Answer: C
Objective: 24.6
Global Outcomes: GO2
50) Which of the following does NOT require NAD+?
A) glycolysis
B) transamination
C) citric acid cycle
D) β oxidation
E) oxidative deamination
Answer: B
Objective: 24.6
Global Outcomes: GO2
51) In mammals, the ammonium ion produced in oxidative deamination is
A) excreted in the feces.
B) stored in the liver.
C) converted to uric acid, which is excreted in the urine.
D) converted to urea, which is excreted in the urine.
E) converted to uric acid, which is excreted by the liver.
Answer: D
Objective: 24.7
Global Outcomes: GO2
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52) In the urea cycle, argininosuccinase synthase catalyzes the reaction of arginosuccunate to
A) citurulline.
B) carbomyl phosphate.
C) orthinine.
D) arginine.
E) arginase.
Answer: D
Objective: 24.7
Global Outcomes: GO2
53) Which metabolic substrate can be produced from the carbon atoms in the amino acid lysine?
A) pyruvate
B) succinyl CoA
C) acetoacetyl CoA
D) fumarate
Answer: C
Objective: 24.8
Global Outcomes: GO2
54) Which metabolic substrate can be produced from the carbon atoms in the amino acid phenylalanine?
A) pyruvate
B) succinyl CoA
C) acetoacetyl CoA
D) fumarate
Answer: D
Objective: 24.8
Global Outcomes: GO2
55) Which metabolic substrate can be produced from the carbon atoms in the amino acid valine?
A) pyruvate
B) succinyl CoA
C) acetoacetyl CoA
D) fumarate
Answer: B
Objective: 24.8
Global Outcomes: GO2
56) All of the nonessential amino acids can be synthesized in the body by transamination, using an amino
group from
A) glutamate.
B) α-ketoglutarate.
C) pyruvate.
D) oxaloacetate.
E) lactic acid.
Answer: A
Objective: 24.9
Global Outcomes: GO2
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24.2 True/False Questions
1) Fatty acids can be used in the brain as an energy source.
Answer: FALSE
Objective: 24.1
Global Outcomes: GO2
2) Red blood cells have mitochondria, which serve as an energy production site.
Answer: FALSE
Objective: 24.1
Global Outcomes: GO2
3) Chylomicrons consist of bile salts and lipids.
Answer: FALSE
Objective: 24.1
Global Outcomes: GO2
4) β oxidation adds two-carbon segments to a fatty acid chain.
Answer: FALSE
Objective: 24.2
Global Outcomes: GO2
5) A ten carbon saturated fatty acid will undergo five β oxidation cycles.
Answer: FALSE
Objective: 24.3
Global Outcomes: GO4
6) Each acetyl CoA that enters the citric acid cycle yields 10 ATP.
Answer: TRUE
Objective: 24.3
Global Outcomes: GO4
7) A ten carbon saturated fatty acid will produce five acetyl CoAs.
Answer: TRUE
Objective: 24.3
Global Outcomes: GO4
8) The production of new triacylglycerols is termed ketogenesis.
Answer: FALSE
Objective: 24.4
Global Outcomes: GO2
9) A low level of acetyl CoA in the cell leads to ketogenesis.
Answer: FALSE
Objective: 24.4
Global Outcomes: GO2
10) Acyl carrier protein is used in fatty acid synthesis.
Answer: TRUE
Objective: 24.5
Global Outcomes: GO2
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11) Protein digestion begins in the small intestine.
Answer: FALSE
Objective: 24.6
Global Outcomes: GO2
12) Some amino acids can be converted into others via transamination.
Answer: TRUE
Objective: 24.6
Global Outcomes: GO2
13) The overall process of synthesizing and breaking down proteins is called protein turnover.
Answer: TRUE
Objective: 24.6
Global Outcomes: GO2
14) Ammonium ions and carbon dioxide produce urea in the urea cycle.
Answer: TRUE
Objective: 24.7
Global Outcomes: GO2
15) The urea cycle is the major pathway for eliminating the excess nitrogen from amino acid degradation.
Answer: TRUE
Objective: 24.7
Global Outcomes: GO2
16) The amino acid valine enters the citric acid cycle as succinyl CoA.
Answer: TRUE
Objective: 24.8
Global Outcomes: GO2
17) Nonessential amino acids can be made by transamination.
Answer: TRUE
Objective: 24.9
Global Outcomes: GO2
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24.3 Matching Questions
Match the following.
A) FAD
B) chylomicrons
C) essential amino acid
D) ATP
E) a ketogenic amino acid
F) Coenzyme A.
G) ketone bodies
H) transaminated amino acid
I) GTP
J) alkalosis
K) acidosis
L) a glucogenic amino acid
M) β oxidation
1) compounds produced when there is little or no carbohydrate metabolism and a subsequent increase in
fat metabolism
Objective: 24.4
Global Outcomes: GO2
2) a carrier of electrons to the site of ATP production, from oxidation reactions involving carbon-carbon
double bonds
Objective: 24.2
Global Outcomes: GO2
3) lipoproteins formed from triacylglycerols and protein
Objective: 24.1
Global Outcomes: GO2
4) an amino acid that is not synthesized in the body
Objective: 24.9
Global Outcomes: GO2
5) a major step in fatty acid degradation
Objective: 24.2
Global Outcomes: GO2
6) an amino acid producing carbons for glucose production
Objective: 24.8
Global Outcomes: GO2
7) a condition of low blood pH
Objective: 24.4
Global Outcomes: GO2
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8) the products of ketogenesis
Objective: 24.4
Global Outcomes: GO2
9) the main source of energy in the body
Objective: 24.1
Global Outcomes: GO2
10) a carrier of 2-carbon units in fatty acid degradation
Objective: 24.5
Global Outcomes: GO2
Answers: 1) G 2) A 3) B 4) C 5) M 6) L 7) K 8) G 9) D 10) F
Identify each of the following metabolic pathways.
A) lipogenesis
B) transamination
C) oxidative deamination
D) β oxidation
E) ketogenesis
11) the conversion of fatty acids to 2-carbon units of acetyl CoA
Objective: 24.2
Global Outcomes: GO2
12) the conversion of an amino acid to an α-keto acid
Objective: 24.9
Global Outcomes: GO2
13) the combination of 2-carbon units of acetyl CoA to form fatty acids
Objective: 24.5
Global Outcomes: GO2
14) the removal of an amino group as NH4+ from glutamate to yield α-ketoglutarate
Objective: 24.6
Global Outcomes: GO2
15) the production of ketone bodies
Objective: 24.4
Global Outcomes: GO2
Answers: 11) D 12) B 13) A 14) C 15) E
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