Part 1

Question 1

What is the primary site of beta-oxidation?

Answer 1

Mitochondria.

Question 2

What is the first step in beta-oxidation?

Answer 2

Activation of fatty acids to acyl-CoA by acyl-CoA synthetase.

Question 3

What is the role of the carnitine shuttle in beta-oxidation?

Answer 3

Transports long-chain fatty acyl-CoA into the mitochondria for oxidation.

Question 4

What are the key enzymes involved in beta-oxidation?

Answer 4

1. Acyl-CoA dehydrogenase, 2. Enoyl-CoA hydratase, 3. Hydroxyacyl-CoA dehydrogenase, 4. Thiolase.

Question 5

What is the energy yield from the complete oxidation of palmitic acid (16:0)?

Answer 5

106 ATP (7 NADH, 7 FADH2, and 8 acetyl-CoA).

Question 6

What is the primary site of fatty acid synthesis?

Answer 6

Cytoplasm.

Question 7

What is the precursor for fatty acid synthesis?

Answer 7

Acetyl-CoA.

Question 8

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

Answer 8

Acetyl-CoA carboxylase (ACC).

Question 9

What are the main products of fatty acid synthase?

Answer 9

Palmitate (16:0).

Question 10

What is the role of citrate in fatty acid synthesis?

Answer 10

Citrate transports acetyl-CoA from the mitochondria to the cytoplasm.

Question 11

What coenzyme is required for fatty acid synthesis?

Answer 11

NADPH.

Question 12

What are essential fatty acids and why are they important?

Answer 12

Linoleic acid (18:2, ω6) and alpha-linolenic acid (18:3, ω3); they are precursors for eicosanoids and cell membrane structure.

Question 13

What is the function of arachidonic acid?

Answer 13

Precursor for eicosanoids such as prostaglandins, thromboxanes, and leukotrienes.

Question 14

What are the two pathways of eicosanoid synthesis from arachidonic acid?

Answer 14

1. Cyclooxygenase (COX) pathway for prostanoids, 2. Lipoxygenase (LOX) pathway for leukotrienes and lipoxins.

Question 15

What regulates beta-oxidation?

Answer 15

Malonyl-CoA inhibits carnitine palmitoyltransferase I (CPT-I), preventing fatty acid entry into mitochondria.

Question 16

What regulates fatty acid synthesis?

Answer 16

Acetyl-CoA carboxylase (ACC) is activated by citrate and inhibited by palmitoyl-CoA and phosphorylation.

Question 17

What is the metabolic defect in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency?

Answer 17

Inability to oxidize medium-chain fatty acids, leading to hypoglycemia and hypoketosis.

Question 18

What are the consequences of carnitine deficiency?

Answer 18

Impaired fatty acid transport into mitochondria, resulting in muscle weakness and hypoketotic hypoglycemia.

Question 19

What is Refsum disease?

Answer 19

A defect in phytanic acid metabolism due to deficiency of phytanoyl-CoA hydroxylase, leading to neurological symptoms.