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 Copyright © 2016 Pearson Education, Inc 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 10) The source of energy for red blood cells is A) amino acids B) fatty acids C) glycerol D) glucose E) lactate Answer: D Copyright © 2016 Pearson Education, Inc 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 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 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 Copyright © 2016 Pearson Education, Inc 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 20) Which step is found in the breakdown of a fat? A) an activation that requires 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 Copyright © 2016 Pearson Education, Inc 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 Copyright © 2016 Pearson Education, Inc 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 Copyright © 2016 Pearson Education, Inc 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) B) C) 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) B) C) D) 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) gram of fat produces significantly more ATP than gram of glucose B) fats can make use of the citric acid cycle C) fats make use of β oxidation D) gram of glucose weighs more than gram of fat E) gram of glucose contains more moles than gram of fat Answer: A Objective: 24.3 Global Outcomes: GO2 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 Copyright © 2016 Pearson Education, Inc Answer: E Objective: 24.3 Global Outcomes: GO2 34) Each acetyl CoA produces ATP in the citric acid cycle A) B) 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 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 Copyright © 2016 Pearson Education, Inc 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 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) Copyright © 2016 Pearson Education, Inc 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 10 Copyright © 2016 Pearson Education, Inc 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 αketoglutarate 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 52) In the urea cycle, argininosuccinase synthase catalyzes the reaction of arginosuccunate to A) citurulline B) carbomyl phosphate C) orthinine D) arginine 11 Copyright © 2016 Pearson Education, Inc 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 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 12 Copyright © 2016 Pearson Education, Inc 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 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 13 Copyright © 2016 Pearson Education, Inc 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 14 Copyright © 2016 Pearson Education, Inc 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 15 Copyright © 2016 Pearson Education, Inc 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 16 Copyright © 2016 Pearson Education, Inc ... 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... 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)... 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