Q: Which of the following reactions in β oxidation is responsible for the removal of a two-carbon unit as acetyl-CoA?

Cleavage by β-ketoacyl-CoA thiolase ($$\text{β-Ketoacyl-CoA} + HS-CoA \rightarrow \text{Fatty acyl-CoA (2C shorter)} + \text{Acetyl-CoA})$$

Q: Which of the following equations represents the overall process of palmitate synthesis from acetyl-CoA and malonyl-CoA?

$$8 \text{Acetyl-CoA} + 7 \text{Malonyl-CoA} + 14 \text{NADPH} + 14 \text{H}^+ \rightarrow \text{Palmitate} + 8 \text{CoA} + 7 \text{CO}_2 + 14 \text{NADP}^+ + 6 \text{H}_2O$$

Question 1

Which of the following statements best describes the structural difference between saturated and unsaturated fatty acids, as shown in the first image?

Accepted Answer

Saturated fatty acids contain only single bonds in their hydrocarbon chain, while unsaturated fatty acids contain at least one double bond.

Question 2

During fatty acid biosynthesis, which molecule acts as the three-carbon intermediate required for chain elongation?

Accepted Answer

Malonyl-CoA

Question 3

Which enzyme catalyzes the irreversible carboxylation of acetyl-CoA to form malonyl-CoA?

Accepted Answer

Acetyl-CoA carboxylase

Question 4

In the process of fatty acid activation prior to β oxidation, which of the following reactions occurs?

Accepted Answer

A fatty acid reacts with CoA and ATP to form fatty acyl-CoA, AMP, and pyrophosphate ($$CH_3$$-($$CH_2)_n-$$COOH + ATP + CoA \rightarrow $$CH_3$$-($$CH_2)_n-CO-$$SCoA + AMP + PP_i$$)

Question 5

Which transport system is responsible for moving fatty acyl-CoA from the cytosol into the mitochondrial matrix for β oxidation?

Accepted Answer

Carnitine shuttle

Question 6

During β oxidation, which step produces FADH2?

Accepted Answer

The first oxidation step catalyzed by acyl-CoA dehydrogenase ($$R-CH_2$-CH_2$-CO-SCoA + FAD \rightarrow trans-\$$Delta^2$$-Enoyl-CoA + $$FADH_2$$)

Question 7

How many acetyl-CoA molecules are produced from the complete β oxidation of palmitic acid ($$C_{16}$$)?

Accepted Answer

8

Question 8

Which of the following best explains why the β oxidation of unsaturated fatty acids yields less energy than saturated fatty acids?

Accepted Answer

Unsaturated fatty acids skip the FADH2-producing step due to the presence of cis double bonds, resulting in less FADH2 generated.

Question 9

Which of the following reactions in β oxidation is responsible for the removal of a two-carbon unit as acetyl-CoA?

Accepted Answer

Cleavage by β-ketoacyl-CoA thiolase ($$	ext{β-Ketoacyl-CoA} + HS-CoA ightarrow 	ext{Fatty acyl-CoA (2C shorter)} + 	ext{Acetyl-CoA})$$

Question 10

A patient has a genetic defect in carnitine acyltransferase. Which metabolic consequence would you expect?

Accepted Answer

Impaired transport of fatty acids into the mitochondria, resulting in reduced β oxidation and energy production from fats.

Question 11

Which coenzyme is primarily used as a reductant in fatty acid biosynthesis?

Accepted Answer

NADPH

Question 12

In the shuttle for transfer of acetyl groups from mitochondria to cytosol, which molecule is oxidized to generate cytosolic NADPH?

Accepted Answer

Malate

Question 13

Which of the following best describes the role of biotin in fatty acid biosynthesis?

Accepted Answer

Biotin acts as a carrier of CO2 in the carboxylation of acetyl-CoA to malonyl-CoA.

Question 14

Which of the following equations represents the overall process of palmitate synthesis from acetyl-CoA and malonyl-CoA?

Accepted Answer

$$8 	ext{Acetyl-CoA} + 7 	ext{Malonyl-CoA} + 14 	ext{NADPH} + 14 	ext{H}^+ ightarrow 	ext{Palmitate} + 8 	ext{CoA} + 7 	ext{CO}_2 + 14 	ext{NADP}^+ + 6 	ext{H}_2O$$

Question 15

Which of the following is a key regulatory enzyme in fatty acid biosynthesis, and how is it regulated?

Accepted Answer

Acetyl-CoA carboxylase; it is activated by insulin and inhibited by glucagon via phosphorylation.

Question 16

Which of the following best describes the fate of odd-numbered fatty acids during β oxidation?

Accepted Answer

The final cycle yields a propionyl-CoA (C3) group and an acetyl-CoA.

Question 17

Which of the following steps in β oxidation is catalyzed by enoyl-CoA hydratase?

Accepted Answer

Hydration of the trans double bond to form a hydroxyl group on the β carbon ($$trans-\$$Delta^2$$-Enoyl-CoA + H_2O \rightarrow 3-Hydroxyacyl-CoA)$$

Question 18

Which of the following is a real-life consequence of impaired β oxidation in humans?

Accepted Answer

Hypoglycemia and muscle weakness during fasting due to inability to utilize fatty acids for energy.

Lipids: Structure, Biosynthesis, and Oxidation

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