Lipid Metabolism

In an individual fed a balanced diet, which of the following does NOT contribute to the synthesis of fatty acids and triacylglycerols (TAGs) in the liver?

Acyl-carnitine.

Which of the following enzymes is NOT involved in the tricarboxylate transport system?

All are involved in the transport of acetyl-CoA into the cytosol

The activity of lipases is controlled in part by a process known as ____ which functions effectively due to the ____ where lipases are active.

interfacial activation; lipid-water interface

______, a condition in which acetoacetate production exceeds it metabolism and results in a sweet breath odor due to nonenzymatic ___ of acetoacetate to _____.

ketosis; decarboxylation; acetone

The major site of formation of acetoacetate from fatty acids is:

liver

Which of the following is the source of the two carbon fragments in fatty acids biosynthesis?

malonyl CoA

Fatty acid synthesis requires both acetyl-CoA and ________ as initiator molecules.

malonyl-CoA

In which location listed below does the following reaction take place? HMG-CoA → acetoacetate + Acetyl-CoA

mitochondria of liver cells

Which of the following lipoprotein particles delivers TAGs and cholesterol to target tissues from the intestine (GI tract)?

CM

Which of the following lipoprotein particles has the greatest relative content (percent weight) of TAGs?

CM

Which carbons in fat, if any, can be converted to glucose?

Carbons from the glycerol backbone and certain carbons from odd chain fatty acids.

Which of the following plays NO role in the synthesis of fatty acids in the liver?

Carnitine

Some athletes believe that dietary carnitine supplements will enhance their ability to perform aerobic exercise. Which of the following statements best describes the "scientific" basis of this belief?

Carnitine is required in the transport of fatty acids into the mitochondrial matrix, and so increasing the amount of carnitine will increase the rate of transport.

Which of the following statements most accurately describes the role of malonyl-CoA in fatty acid synthesis?

It is a temporary "store" of free energy which enables the formation of a new carbon-carbon bond in the growing fatty acyl-chain.

After 3 rounds of β-oxidation, a fatty acyl-CoA intermediate is produced which is designated 12:2Δ3,6. At this point in the process (production of a fatty acyl-CoA intermediate designated 12:2Δ3,6), which of the following is TRUE of the next enzyme-catalyzed reaction?

It is an isomerization.

Which of the following statements about lipolysis in adipocytes is TRUE?

It is increased in response to a glucagon signal.

Which of the following lipoprotein particles is converted into LDL via the action of lipoprotein lipase?

VLDL

Which of the following components would be condensed to form acetoacetate?

acetyl CoA and acetyl-CoA

Free fatty acids bind to ________ for circulation in the bloodstream.

albumin

Which of the following diets would most likely promote the formation of ketone bodies?

high fat, high protein, low carbohydrate

Which of the following would result in a net increase in uptake of LDL by the liver?

high levels of cholesterol synthesis

Which of the following enzymes is NOT activated by insulin?

hormone sensitive lipase

Where does the process of lipolysis occur? i) skeletal muscle ii) adipose tissue iii) intestine iv) blood vessel walls

ii, iii, and iv

Which of the following statements about lipases is/are TRUE?1 Pancreatic lipases break down TAGs in the intestine.2 Hormone-sensitive lipase is located primarily in the liver.3 Lipoprotein lipase is located in blood vessel walls.4 Lipoprotein lipase helps deliver cholesterol in peripheral tissues.

1 and 3

The inner mitochondrial membrane contains a specific transporter protein for which of the following substances1 pyruvate2 fatty acyl-CoA3 PEP4 acetyl-CoA5 Pi

1, 3, 5

The complete combustion of palmitate and glucose yields 9781 kJ · mol-1 and 2850 kJ · mol-1 of free energy, respectively. Palmitate oxidation produces ______ ATP and glucose catabolism produces ______ ATP. The standard free energy of ATP synthesis from ADP + Pi is ______ kJ · mol-1. Palmitate catabolism therefore has an efficiency of ______%. Likewise, glucose catabolism has an efficiency of ______%. Thus, the two processes have very nearly the same overall efficiency.

106 32 30.5 33 34

If 1 mol of a fatty acyl-CoA containing 20 carbon atoms undergoes three rounds of β-oxidation, how many mol of ATP are produced from the complete aerobic catabolism of the products of these three rounds? Assume that re-oxidation of NADH via the electron transport chain yields the equivalent of 3 ATP, and that re-oxidation of FADH2 yields 2 ATP. (The remaining acyl-CoA is NOT catabolized further.)

51 ATP

How many molecules of water are produced by the electron transport chain during the complete aerobic oxidation of 1 molecule of stearate (C18:0) to CO2 and water?

52 H2O

What are the major products produced by β-oxidation of the acyl-CoA heptadecanoyl-CoA (17:0)?

7 Acetyl-CoA, 7 FADH2, 7 NADH, 1 Propionyl-CoA

If the fatty acid 12:1Δ7 is completely catabolized to CO2 and H2O, what would be the net yield of ATP? (Assume that re-oxidation of NADH via the electron transport chain yields the equivalent of 3 ATP, and that re-oxidation of FADH2 yields 2 ATP.)

93 ATP

If the 14-carbon saturated fatty acid myristoyl-CoA is oxidized completely to carbon dioxide and water (via the β-oxidation pathway, the citric acid cycle and oxidative phosphorylation), what is the yield of ATP per molecule of myristoyl-CoA? (Assume that re-oxidation of NADH via the electron transport chain yields the equivalent of 2.5 ATP, and that re-oxidation of FADH2 yields 1.5 ATP.)

94 ATP

For the following process, indicate whether it is activated (A) or inhibited (B) during FASTING.Lipolysis in adipocytes. (A/B)

A

The mitochondria of brown adipose tissue contain an additional protein called the "uncoupling protein", which is an H+ ion channel that spans the inner mitochondrial membrane. Which one of the following would result when the uncoupling protein is active?

A significant increase in heat.

Which of the following sets of molecules is required prior to the -oxidation of a fatty acid?

ATP, carnitine, and coenzyme A.

For the following enzyme, indicate whether it is activated (A) or inhibited (B) during FASTING.Acetyl-CoA carboxylase in the liver. (A/B)

B

How will the carbon atoms from an odd numbered fatty acid enter the citric acid cycle?

As acetyl-CoA and succinyl-CoA.

Which of the following vitamins is part of the prosthetic group 5-deoxyadenosylcobalamin?

B12

Considering the figure below, what compound would be formed by action of acyl-CoA dehydrogenase?

CH3-(CH2)n-C=C-C=SCoA H H //O

Which of the following does NOT play a role in determining the rate of cholesterol synthesis in humans?

Glycogen

The glycerol backbone of triacylglycerols is catabolized to ________ .

Dihydroxyacetone phosphate

Triacylglycerols are synthesized by ____ during times of starvation via a process known as ____.

Dihydroxyacetone phosphate; glyceroneogenesis

Individuals with significantly reduced levels of carnitine in muscle cells suffer from weakness, even during moderate exercise. This is because:

None of these reasons.

Why does the catabolism of fat produce more energy than an equivalent mass of carbohydrate?

Fat catabolism produces more reduced cofactors gram per gram.

Fat is a more efficient store of energy than carbohydrate. Which of the following is NOT a factor in this?

Fat is catabolized only aerobically; carbohydrate can be catabolized anaerobically.

During starvation, what is the MAJOR fuel source for the production of ketone bodies?

Fats stored in adipose tissue.

The antidiabetes drugs known as thiazolidinediones induce the production of glycerol kinase in adipocytes. This would decrease the concentration of serum fatty acids, which are often elevated in diabetics. Glycerol kinase converts _____ to _____ , a precursor for _______ synthesis. By promoting ______ synthesis, the drug decreases the concentration of unesterified fatty acids in the body.

Glycerol Glycerol-3-Phosphate Triacylglycerol Triacylglycerol

Cholesterol and other lipids are transported from tissues to the liver by ________.

HDL

Which of the following lipoprotein particles has the greatest relative content (percent weight) of proteins?

HDL

Which of the following accurately ranks lipoproteins from highest to lowest density?

HDL > LDL > IDL > VLDL > chylomicrons

Under which one of the following conditions does the biosynthesis of fatty acids in the liver mainly occur?

High carbohydrate intake.

The rate of breakdown of TAGs in adipocytes is determined by the activity of which of the following enzymes?

Hormone-sensitive lipase

Which of the following is required for entry of fatty acids into the oxidation pathway?I. priming via the enzyme acyl CoA synthetaseII. conservation of free energy from ATP hydrolysis by use of a thioester linkageIII. transport to the cytosol for oxidation via a carnitine carrier proteinIV. hydrolysis of carnitine palmitoyl transfer protein

I, II

Which of the following is TRUE regarding the enzyme acetyl-CoA carboxylase?I. It catalyzes the first committed step in fatty acid oxidation.II. It requires S-adenosylmethionine.III. It produces malonyl CoA.IV. It uses acetyl CoA.

III, IV

What role does serum albumin play in fat metabolism?

It acts as a carrier for free fatty acids in the bloodstream.

Which of the following statements about lipolysis in adipocytes is FALSE?

Its rate is determined by substrate supply. (This statement is FALSE. Lipolysis (hormone-sensitive lipase) is regulated by hormone-signalling mechanisms and is not affected by the levels of TAGs in adipocytes.)

Which of the following statements about ketone bodies is FALSE?

Ketone bodies are produced by the liver when fatty acid supplies are limited.

In the following equation, which substance is being oxidized?L--hydroxy-acyl-CoA + NAD+ -ketoacyl-CoA + NADH + H+

L--hydroxy-acyl-CoA

Cells take up ____ by receptor mediated endocytosis.

LDL

Which of the following lipoprotein particles has the greatest relative content (percent weight) of cholesteryl-esters?

LDL

Complete the following sentence. The catabolism of unsaturated fatty acids, as compared to saturated fatty acids, results in:

Less ATP synthesis because they are more oxidized.

Which of the following terms is used to describe the breakdown of triacylglycerols into free fatty acids and glycerol?

Lipolysis

Where are the two major sites for fatty acid catabolism in the body?

Liver and skeletal muscle.

Which of the following statements about peroxisomes is FALSE?

Long chain fatty acids are transported into the peroxisome via a carnitine carrier protein where they are activated for oxidation.

Which of the following has NO EFFECT on the activity of acetyl-CoA carboxylase?

Malonyl-CoA

Which of the following statements about malonyl-CoA is FALSE?

Malonyl-CoA is an intermediate of cholesterol synthesis.

In which cellular compartment are ketone bodies synthesized?

Mitochondrial matrix.

Which of the following correctly identifies the four reactions of -oxidation and their sequence?

Oxidation, hydration, oxidation, thiolysis.

Which of the following statements about phosphatidate is correct?

Phosphatidic acid can be derived from dihydroxyacetone phosphate.

What is the rate-limiting step in fatty acid synthesis?

The carboxylation of acetyl-CoA.

Which of the following is NOT true of the rate-limiting reaction in fatty acid synthesis?

The enzyme that catalyzes this reaction is inhibited by citrate.

If the concentration of component R was lowered in a muscle cell, compared with normal, what would be the effect on the maximal rate of oxygen consumption in that cell, if it were provided with glucose as a fuel molecule?

The maximal rate of oxygen consumption would be unaltered.

Which of the following affects the rate of -oxidation?

The rate of electron transport. (This statement is TRUE. "Energy demand" affects the rate of-oxidation significantly. When energy demands in the cell are high, the electron transport chain re-oxidizes NADH and FADH2 generating NAD+ and FAD. High levels of NAD+ and FAD enhance the rate of-oxidation.)

In adipocytes, why does the synthesis of triacylglycerols require an external supply of glucose?

The synthesis of triacylglycerols requires glycerol 3-phosphate, which is derived from glucose.

Which of the following is NOT a part of receptor-mediated endocytosis of LDL?

The α-helices of apolipoprotein A-I float on the surface of the lipoprotein.

In which of the following ways are fatty acid synthesis and β-oxidation similar?

Their use of a repetitive series of redox and addition/elimination reactions.

Which of the following is an important physiological role of bile salts?

They assist in the digestion of lipids.

Which one of the following statements about acetoacetate and 3-hydroxybutyrate is FALSE?

They may be regarded as water-soluble, transportable forms of citrate in the blood.

Consider the fatty acid below:

This fatty acid (linolenate) cancannot be synthesized by animals because it contains a double bond closer than 234567 carbons from its noncarboxylate end.

Which of the following is the starting metabolite in ketone body biosynthesis?

acetyl CoA

How are ketone bodies transported in the bloodstream?

beta-hydroxybutyrate

Digestion of triacylglycerols is aided by the cholesterol derivatives synthesized by the liver known as

bile acids

What is the final product of fatty acid synthesis?

palmitate

Acyl carrier protein (ACP) contains a ________ prosthetic group.

phosphopantetheine

The oxidation of odd-numbered fatty acids results in ________ as a final product.

propionyl-CoA