Q: Which enzyme catalyzes the activation of fatty acids for β-oxidation, and what is the reaction it catalyzes?

Fatty acyl-CoA synthetase; $$ \text{Fatty acid} + \text{CoA} + ATP \rightarrow \text{Fatty acyl-CoA} + AMP + 2Pi $$

Q: Which of the following is the correct net reaction for the synthesis of palmitate ($$C_{16}) $$from acetyl-CoA?

$$8 \text{Acetyl-CoA} + 7 \text{ATP} + 14 \text{NADPH} + 14 \text{H}^+ \rightarrow \text{Palmitate} + 8 \text{CoA} + 7 \text{ADP} + 7 \text{Pi} + 14 \text{NADP}^+ + 6 \text{H}_2O$$

Question 1

Which of the following best explains why fats are considered an efficient way to store fuel in biological systems?

Accepted Answer

Fats yield more ATP per gram upon complete oxidation compared to carbohydrates.

Question 2

Which enzyme catalyzes the activation of fatty acids for β-oxidation, and what is the reaction it catalyzes?

Accepted Answer

Fatty acyl-CoA synthetase; $$ 	ext{Fatty acid} + 	ext{CoA} + ATP ightarrow 	ext{Fatty acyl-CoA} + AMP + 2Pi $$

Question 3

Which of the following statements about the urea cycle is correct?

Accepted Answer

The urea cycle detoxifies ammonia by converting it to urea for excretion.

Question 4

Which of the following best describes the difference between nucleosides and nucleotides?

Accepted Answer

Nucleosides contain a nitrogenous base and a sugar; nucleotides contain a base, sugar, and one or more phosphate groups.

Question 5

Which of the following amino acids is classified as both glucogenic and ketogenic?

Accepted Answer

Isoleucine

Question 6

Which coenzyme is required for all transamination reactions in amino acid metabolism?

Accepted Answer

Pyridoxal phosphate (PLP)

Question 7

Which of the following is a product of the catabolism of odd-numbered fatty acids that enters the citric acid cycle?

Accepted Answer

Propionyl-CoA

Question 8

Which process describes the conversion of nitrogen gas ($$N_2) to $$ammonia ($$NH_3) in $$biological systems?

Accepted Answer

Nitrogen fixation

Question 9

Which vitamin is essential as a cofactor in one-carbon transfer reactions during nucleotide biosynthesis?

Accepted Answer

Folic acid (Vitamin B9)

Question 10

Which of the following best explains why mammals require essential fatty acids in their diet?

Accepted Answer

Mammals cannot synthesize double bonds beyond carbon 9 in the fatty acid chain.

Question 11

Which of the following is the correct net reaction for the synthesis of palmitate ($$C_{16}) $$from acetyl-CoA?

Accepted Answer

$$8 	ext{Acetyl-CoA} + 7 	ext{ATP} + 14 	ext{NADPH} + 14 	ext{H}^+ ightarrow 	ext{Palmitate} + 8 	ext{CoA} + 7 	ext{ADP} + 7 	ext{Pi} + 14 	ext{NADP}^+ + 6 	ext{H}_2O$$

Question 12

Which of the following statements about the chemiosmotic theory of ATP production is correct?

Accepted Answer

A proton gradient across the inner mitochondrial membrane drives ATP synthesis via ATP synthase.

Question 13

Which of the following is a key regulatory enzyme in fatty acid synthesis, and what is its regulation mechanism?

Accepted Answer

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

Question 14

Which of the following best describes the role of the glucose-alanine cycle?

Accepted Answer

It transports ammonia from muscle to liver in the form of alanine.

Question 15

Which of the following is a distinguishing feature of the β-oxidation of unsaturated fatty acids compared to saturated fatty acids?

Accepted Answer

It requires additional enzymes such as enoyl-CoA isomerase.

Question 16

Which of the following statements about the biosynthesis of cholesterol is correct?

Accepted Answer

The rate-limiting step is catalyzed by HMG-CoA reductase.

Question 17

Which of the following best describes the difference between the de novo and salvage pathways of nucleotide biosynthesis?

Accepted Answer

De novo pathways synthesize nucleotides from small precursors; salvage pathways recycle bases and nucleosides.

Question 18

Which of the following is a common symptom of an inborn error of amino acid metabolism such as phenylketonuria (PKU)?

Accepted Answer

Accumulation of phenylalanine and its derivatives in the blood

Question 19

Which of the following best explains why the catabolism and anabolism of fatty acids are not simply the reverse of each other?

Accepted Answer

They occur in different cellular compartments and use different cofactors.

BCM 261: Lipid and Nitrogen Metabolism – Study Guide Summary

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