CHAPTER 27

How many rounds of β oxidation would be required for a 16-carbon fatty acyl chain to be degraded to acetyl CoA? 16 8 7 15 10

7

β oxidation of myristyl-CoA (14:0) yields: 7 acetyl CoA + 7 FADH2 + 7 NADH + 7 H+. 6 acetyl CoA + 7 FADH2 + 7 NADH + 7 H+. 7 acetyl CoA + 6 FADH2 + 6 NADH + 6 H+. 7 acetyl CoA + 7 FAD + 7 NAD+. 14 acetyl CoA + 12 FADH2 + 12 NADH + 12 H+.

7 acetyl CoA + 6 FADH2 + 6 NADH + 6 H+.

Which statement about ketone bodies is TRUE? Acetone and D-3-hydroxybutyrate can be obtained from acetoacetate. Ketone bodies bind to the blood protein albumin, which delivers them to tissues. Ketone bodies increase the blood pH. Ketone bodies are the main fuel during short-term starvation. During starvation, acetoacetate can be captured to synthesize glucose.

Acetone and D-3-hydroxybutyrate can be obtained from acetoacetate.

How does formation of acetyl CoA by β oxidation not only provide energy for cellular respiration but also spare glucose? As acetyl CoA levels increase during lipid metabolism, D-3-hydroxybutyrate is reduced to pyruvate for gluconeogenesis. Acetyl CoA provides carbon for the formation of oxaloacetate, which in turn can be decarboxylated to form pyruvate. Acetyl CoA can be converted to acetoacetate and from there to lactate for anaerobic metabolism. Acetyl CoA derived from fatty acids inhibits pyruvate dehydrogenase, the enzyme that converts pyruvate into acetyl CoA. Acetyl CoA derived from fatty acids activates pyruvate carboxylase, stimulating gluconeogenesis.

Acetyl CoA derived from fatty acids inhibits pyruvate dehydrogenase, the enzyme that converts pyruvate into acetyl CoA.

The activation of fatty acids for degradation takes place in two steps. What is the intermediate formed and why is activation necessary for β oxidation to occur? Acyl adenylate; cAMP formed by this reaction activates protein kinase A. Acyl adenylate; only the activated form of the fatty acid can react with coenzyme A. Propionate; only the activated form of the fatty acid can react with coenzyme A. Acyl carnitine; cAMP formed by this reaction activates protein kinase A. Acyl carnitine; this intermediate is needed to fuel the carnitine cycle.

Acyl adenylate; only the activated form of the fatty acid can react with coenzyme A.

Which statement about starvation is TRUE? Plasma levels of fatty acids and ketone bodies decrease, whereas the plasma level of glucose increases. Carbohydrate reserves are exhausted in a single day. Triacylglycerol reserves are exhausted in a single month. Plasma levels of fatty acids and glucose bodies decrease, whereas the plasma level of ketone bodies increases. During starvation, the liver cells convert any available acetyl CoA, lactate, and alanine to glucose for the brain's needs.

Carbohydrate reserves are exhausted in a single day.

Which enzyme catalyzes the conversion of acetoacetate into D-3-hydroxybutyrate? D-3-hydroxybutyrate dehydrogenase hydroxymethylglutaryl CoA cleavage enzyme 3-ketothiolase hydroxymethylglutaryl CoA synthase CoA transferase

D-3-hydroxybutyrate dehydrogenase

Choose the CORRECT sequence of utilization of D-3-hydroxybutyrate. D-3-hydroxybutyrate is oxidized to acetoacetate → acetoacetate converts into acetoacetyl CoA → acetoacetyl CoA converts into 2 molecules of acetyl CoA, which enter the citric acid cycle D-3-hydroxybutyrate is oxidized to acetoacetate → acetoacetate converts into acetoacetyl CoA → acetoacetyl CoA converts into CO2 and acetyl CoA, which enter the citric acid cycle D-3-hydroxybutyrate converts into acetone by D-3-hydroxybutyrate dehydrogenase D-3-hydroxybutyrate converts into acetoacetate by D-3-hydroxybutyrate dehydrogenase → acetoacetate spontaneously converts into acetone, which enters gluconeogenesis D-3-hydroxybutyrate is oxidized to acetoacetate → acetoacetate converts into acetoacetyl CoA → acetoacetyl CoA converts into 2 molecules of pyruvate, which enter the citric acid cycle

D-3-hydroxybutyrate is oxidized to acetoacetate → acetoacetate converts into acetoacetyl CoA → acetoacetyl CoA converts into 2 molecules of acetyl CoA, which enter the citric acid cycle

Coenzyme(s) involved in the degradation of saturated fatty acyl CoA include(s): FAD. NAD+. TPP. FAD and NAD+. All of the answers are correct.

FAD and NAD+.

The products of lipolysis are glycerol and free fatty acids. What is the role of these compounds? Glycerol can be phosphorylated to D-glyceraldehyde 3-phosphate, which can enter both glycolytic and gluconeogenic pathways. Free fatty acids can be oxidized to succinyl CoA, which enters the citric acid cycle. Free fatty acids can be used in both glycolytic and gluconeogenic pathways in the liver cells. Glycerol can be used as a fuel inside cells. Glycerol can be used only in gluconeogenesis in the liver cells. Free fatty acids can be used as a fuel inside cells. Glycerol can be used only in glycolysis in the liver cells. Free fatty acids can be used as a fuel inside cells. Free fatty acids can be oxidized to acyl CoA, which enters the citric acid cycle. Glycerol can be phosphorylated to D-glyceraldehyde 3-phosphate, which can enter both glycolytic and gluconeogenic pathways.

Glycerol can be phosphorylated to D-glyceraldehyde 3-phosphate, which can enter both glycolytic and gluconeogenic pathways. Free fatty acids can be oxidized to succinyl CoA, which enters the citric acid cycle.

How does activated fatty acid move to the mitochondrial matrix? The activated fatty acid moves across the outer mitochondrial membrane through a porin channel. Acetyl carnitine shuttles across the inner mitochondrial membrane by a translocase. The activated fatty acid moves across the outer mitochondrial membrane by passive diffusion. Acetyl carnitine moves across the inner mitochondrial membrane by a translocase. The activated fatty acid moves across the outer mitochondrial membrane through a porin channel, and shuttles across the outer mitochondrial membrane by a translocase. Acetyl carnitine moves across the outer mitochondrial membrane through a porin channel, and shuttles across the outer mitochondrial membrane by a translocase. D-glyceraldehyde 3-phosphate moves across the outer mitochondrial membrane through a porin channel, and shuttles across the outer mitochondrial membrane by a translocase.

The activated fatty acid moves across the outer mitochondrial membrane through a porin channel. Acetyl carnitine shuttles across the inner mitochondrial membrane by a translocase.

Every biochemistry student knows that most naturally occurring unsaturated fatty acids are cis fatty acids. Why, then, do so many fat-containing foods come with the notation "Contains no trans fats"? Vegetable oils contain polyunsaturated fatty acids prone to oxidation, which then converts them to trans fats. Olive oils, normally healthy oils, are converted to trans fat when cooked at high temperatures. Thus, olive oils are used only at low temperatures. Vegetable oils are often hydrogenated to form trans unsaturated fatty acids to preserve shelf life. Oils that contain an odd number of carbon atoms are particularly susceptible to oxidation to trans fats. Thus, no odd-numbered carbon fatty acids are used in these foods. Oils that contain an odd number of carbon atoms are particularly susceptible to reduction to trans fats. Thus, no odd-numbered carbon fatty acids are used in these foods.

Vegetable oils are often hydrogenated to form trans unsaturated fatty acids to preserve shelf life.

What can promote ketone body formation? accumulation of acetyl CoA lack of acetyl CoA high insulin level low glucagon level excessive protein intake

accumulation of acetyl CoA

Acetoacetate is formed from acetyl CoA and can spontaneously turn to: acetone. acyl CoA. acetyl CoA. glucose. pyruvate.

acetone.

Which compound does β oxidation begin from? acetyl CoA trans-Δ2-enoyl CoA acyl CoA CoA acyl carnitine

acyl CoA

Which enzyme is bound to the outer mitochondrial membrane? Select all that apply. acyl CoA synthetase carnitine acyltransferase I translocase carnitine acyltransferase II acyl CoA dehydrogenase

acyl CoA synthetase carnitine acyltransferase I

Which compound is able to move across the inner mitochondrial membrane? glycerol free fatty acid acyl CoA D-glyceraldehyde 3-phosphate acyl carnitine

acyl carnitine

High levels of acetoacetate in blood lead to a decrease in the rate of lipolysis in _______________ tissue.

adipose

Identify the compound shown. (IMAGE) an intermediate in ketogenesis an intermediate in lipolysis an intermediate in fatty acid oxidation an intermediate in fatty acid activation a product of fatty acid activation

an intermediate in fatty acid activation

Choose the CORRECT reaction sequence for the utilization of propionyl CoA. carboxylation to D-methylmalonyl CoA → isomerization to L-methylmalonyl CoA → conversion to succinyl CoA, which enters the citric acid cycle carboxylation to D-methylmalonyl CoA → isomerization to L-methylmalonyl CoA → conversion to acetyl CoA, which enters the citric acid cycle carboxylation to L-methylmalonyl CoA → isomerization to D-methylmalonyl CoA → conversion to acetyl CoA, which enters the citric acid cycle isomerization to trans-Δ2-enoyl CoA → hydration to L-3-hydroxyacyl CoA → oxidation to 3- ketoacyl CoA → thiolysis to acetyl CoA, which enters the citric acid cycle isomerization to trans-Δ2-enoyl CoA → hydration to L-3-hydroxyacyl CoA → oxidation to 3- ketoacyl CoA → conversion to acetyl CoA, which enters the citric acid cycle

carboxylation to D-methylmalonyl CoA → isomerization to L-methylmalonyl CoA → conversion to succinyl CoA, which enters the citric acid cycle

Untreated, chronic ketone body production will: increase blood pH levels. decrease blood pH levels. increase blood glucose levels. decrease hydrogen ion concentration in blood. increase bicarbonate concentration in blood.

decrease blood pH levels.

In the absence of insulin, most acetyl CoA: enters the citric acid cycle. enters ketogenesis. enters gluconeogenesis. is released into blood. is stored as lipid droplets.

enters ketogenesis.

The hormone induces lipolysis, whereas inhibits the process. epinephrine; adrenocorticotropin glucagon; insulin insulin; norepinephrine glucagon; epinephrine epinephrine; glucagon

glucagon; insulin

Which organs or tissues prefer to use ketone bodies such as acetoacetate as a fuel energy source instead of glucose? heart muscle renal cortex brain heart muscle and renal cortex liver

heart muscle and renal cortex

Exercising first thing in the morning without eating mobilizes lipid stores for fuel. All of the below are involved in this mobilization, EXCEPT: glucagon binds 7TM receptors that activate adenylate cyclase. perilipin is phosphorylated. cAMP stimulates protein kinase A. hormone-sensitive lipase completes the mobilization of fatty acids with the production of a free fatty acid and glycerol. hormone-sensitive lipase is phosphorylated.

hormone-sensitive lipase completes the mobilization of fatty acids with the production of a free fatty acid and glycerol.

Which process makes the following reaction irreversible? RCOO- + CoA RCO-CoA +AMP +PPi hydrolysis of inorganic pyrophosphate hydrolysis ATP heat release AMP release catalysis by acyl CoA synthetase

hydrolysis of inorganic pyrophosphate

High cAMP concentration: inhibits lipolysis in the liver cells. activates β oxidation of fatty acids in the mitochondrial matrix. decreases the level of free fatty acids in blood. increases the level of free fatty acids in blood. inhibits β oxidation of fatty acids in the mitochondrial matrix.

increases the level of free fatty acids in blood.

D-glyceraldehyde 3-phosphate can be converted: into pyruvate or glucose in the liver. only into pyruvate in the liver. only into glucose in muscles. only into acetyl CoA in muscles. only into acetyl CoA in the liver.

into pyruvate or glucose in the liver.

What does muscle weakness and cramping affecting skeletal muscle, the heart, and kidneys likely indicate? excess carnitine in the diet loss of hormone-sensitive lipase activity malfunctioning or deficient carnitine translocase ketone-body production ketogenic diet

malfunctioning or deficient carnitine translocase

Which of the following compounds is toxic? acetoacetate cobalamin hypoglycin methylene cyclopropylacetate trans-Δ3-enoyl CoA

methylene cyclopropylacetate

Hormone-sensitive lipase acts in: fatty acid β oxidation. transport of a fatty acid through blood. thiolysis in the mitochondrial matrix. mobilization of triacylglycerols. hydrolysis of triacylglycerols in the mitochondrial matrix.

mobilization of triacylglycerols.

During triacylglycerol hydrolysis, hormone-sensitive lipase catalyzes the release of: monoacylglycerol and two free fatty acids. diacylglycerol and a single free fatty acid. glycerol and three free fatty acids. monoacylglycerol and a single free fatty acid. glycerol and a single free fatty acid.

monoacylglycerol and a single free fatty acid.

Select all that apply. Epidemiological evidence suggests that consumption of a large amount of saturated fatty acids and trans fat promotes: obesity. type 2 diabetes. type 1 diabetes. atherosclerosis. thrombosis.

obesity. type 2 diabetes. atherosclerosis. thrombosis.

The availability of ______________ determines whether acetyl CoA, made from fatty acids, can enter the citric acid cycle. pyrophosphate pyruvate dehydrogenase oxaloacetate cobalamin β hydroxybutyrate

oxaloacetate

The first step of β oxidation is: oxidation by FAD. oxidation by NAD+. hydration by enoyl CoA hydrase. thiolysis by CoA. activation by CoA.

oxidation by FAD.

What protein triggers mobilization of triacylglycerols? hormone-sensitive lipase adipose triglyceride lipase perilipin phosphorylase kinase cyclic AMP

perilipin

The main priority of metabolism during starvation is: providing sufficient glucose to the muscles. preserving muscle proteins. providing the process of gluconeogenesis. preserving liver proteins. providing the citric acid cycle.

preserving muscle proteins.

Methylmalonyl CoA mutase contains vitamin B12 as its coenzyme. What is the substrate for this enzyme? propionyl CoA D-glyceraldehyde 3-phosphate succinyl CoA trans-Δ2-enoyl CoA trans-Δ3-enoyl CoA

propionyl CoA

The increase in acetyl CoA during starvation inhibits the enzyme: acyl CoA dehydrogenase. cobalamin. glucagon. hormone-sensitive lipase. pyruvate dehydrogenase.

pyruvate dehydrogenase.

The ketogenic diet: kills the intestinal flora. decreases blood pH. is the only way to treat epilepsy. increases seizures in children with epilepsy. requires high-fat, adequate-protein, and low-carbohydrate consumption.

requires high-fat, adequate-protein, and low-carbohydrate consumption.

What is the function of cis-Δ3-enoyl CoA isomerase? conversion of cis-Δ3 double bond into trans-Δ3 single bond conversion of trans-Δ2 double bond to cis-Δ3 double bond shift the position of the double bond for the proper work of acyl CoA dehydrogenase reduction of 2,4-dienoyl to cis-Δ3-enoyl CoA reduction of 2,4-dienoyl to trans-Δ2-enoyl CoA

shift the position of the double bond for the proper work of acyl CoA dehydrogenase

The main site of ketogenesis is: the liver cells. the muscles cells. neurons. blood plasma. adipocytes.

the liver cells.

Which enzyme-substrate pair is CORRECT? methylmalonyl CoA mutase - 3-hydroxy-3-methyl-glutaryl CoA hydroxymethylglutaryl CoA synthase - L-methylmalonyl CoA cis-Δ3-enoyl CoA isomerase - trans-Δ3-enoyl CoA thiolase - 3-ketoacyl CoA acyl CoA synthetase - acetyl CoA

thiolase - 3-ketoacyl CoA

What stereoisomer is a regular substrate in the β oxidation pathway? trans-Δ2-enoyl CoA cis-Δ12-enoyl CoA trans-Δ3-enoyl CoA cis-Δ3-enoyl CoA cis-Δ9-enoyl CoA

trans-Δ2-enoyl CoA

Phosphorylation of perilipin: triggers the release of a coactivator for adipose triglyceride lipase. stimulates phosphorylation of protein kinase A. activates adenylate cyclase. initiates the release of a fatty acid from triacylglycerol. activates hormone-sensitive lipase.

triggers the release of a coactivator for adipose triglyceride lipase.

Where is adipose tissue located in a human body? under the skin (subcutaneous fat) and around the inner organs (visceral fat) under the skin (visceral fat) and around the inner organs (subcutaneous fat) under the skin (subcutaneous fat), around the inner organs (visceral fat), and in the liver under the skin (subcutaneous fat) and around the inner organs (blubber) inside muscle tissue

under the skin (subcutaneous fat) and around the inner organs (visceral fat)

The compound is considered one of the ketone bodies. pyrophosphate glucagon cobalamin β hydroxybutyrate oxaloacetate

β hydroxybutyrate

During starvation, the brain begins to consume an appreciable amount of ketone bodies days after the beginning of the starvation state. 3 7 14 1 30

3

How many molecules of acetyl CoA are involved in a single round of ketogenesis? 2 3 4 1 0

3

Which compound is an intermediate in ketogenesis? 3-hydroxy-3-methyl-glutaryl CoA D-3-hydroxybutyrate acetone D-methylmalonyl CoA L-methylmalonyl CoA

3-hydroxy-3-methyl-glutaryl CoA