Question 1

Which of the following statements best describes the main regulatory enzyme of fatty acid synthesis, and how is it regulated?

Accepted Answer

Acetyl-CoA carboxylase; activated by citrate and inhibited by palmitoyl-CoA.

Question 2

During starvation, increased fatty acid oxidation in the liver leads to the production of which compounds, and what is their primary physiological role?

Accepted Answer

Ketone bodies; serve as alternative energy sources for the brain and muscles.

Question 3

Which of the following equations correctly represents the carboxylation of acetyl-CoA to malonyl-CoA during fatty acid synthesis?

Accepted Answer

$$\mathrm{Acetyl{-}CoA} + \mathrm{CO}_2 + \mathrm{ATP} \rightarrow \mathrm{Malonyl{-}CoA} + \mathrm{ADP} + \mathrm{P_i}$$

Question 4

A patient is prescribed a drug that inhibits phospholipase A2. What is the most likely effect on eicosanoid synthesis?

Accepted Answer

Decreased release of arachidonic acid from membrane phospholipids, reducing eicosanoid synthesis.

Question 5

Which of the following best explains why unsaturated fatty acids (USFAs) are important for membrane structure?

Accepted Answer

USFAs, especially in the cis configuration, increase membrane fluidity.

Question 6

Which enzyme is directly inhibited by glucocorticoids, and what is the consequence for inflammatory mediator production?

Accepted Answer

Phospholipase A2; decreased arachidonic acid release and reduced eicosanoid synthesis.

Question 7

Which of the following is a correct description of the fate of acetyl-CoA during ketogenesis in the liver?

Accepted Answer

Acetyl-CoA is used to synthesize ketone bodies such as acetoacetate and D-β-hydroxybutyrate.

Question 8

Which of the following fatty acids is considered essential in the human diet and serves as a precursor for eicosanoid synthesis?

Accepted Answer

Linoleic acid

Question 9

A mutation in the enzyme carnitine acyltransferase I would most directly impair which metabolic process?

Accepted Answer

Transport of fatty acids into the mitochondria for β-oxidation.

Question 10

Which of the following best describes the role of NADPH in fatty acid synthesis?

Accepted Answer

NADPH provides reducing equivalents for the biosynthetic reactions catalyzed by fatty acid synthase.

Question 11

Which of the following reactions is catalyzed by β-ketoacyl synthase during fatty acid synthesis?

Accepted Answer

$$\mathrm{Acetyl{-}ACP} + \mathrm{Malonyl{-}ACP} \rightarrow \mathrm{Acetoacetyl{-}ACP} + \mathrm{ACP} + \mathrm{CO}_2$$

Question 12

Which of the following best explains why fatty acid oxidation and synthesis do not occur simultaneously in the same cellular compartment?

Accepted Answer

Fatty acid oxidation occurs in the mitochondria, while synthesis occurs in the cytosol, preventing futile cycling.

Question 13

Which of the following is a direct consequence of increased intracellular Ca$$^{2+}$$ and calmodulin activation in a cell membrane?

Accepted Answer

Activation of membrane-bound phospholipase A2, leading to arachidonic acid release.

Question 14

Which of the following best describes the fate of palmitate after its synthesis in the cytosol?

Accepted Answer

It is elongated and desaturated in the endoplasmic reticulum or mitochondria to form longer and unsaturated fatty acids.

Question 15

Which of the following statements about the synthesis of ketone bodies is correct?

Accepted Answer

Ketone bodies are produced in the liver mitochondria from acetyl-CoA during periods of low carbohydrate availability.

Question 16

Which of the following best explains why palmitic and stearic acids are the most abundant fatty acids in animal lipids?

Accepted Answer

They are the primary products of fatty acid synthase activity in the liver.

Fatty Acids, Eicosanoids, and Lipid Metabolism

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