Lipids and Membranes Flashcards

Beta-oxidation of fatty acids occurs primarily in which cellular compartment?

Answer: Mitochondrial matrix

Beta-oxidation of most fatty acids occurs in the mitochondrial matrix, where fatty acyl-CoA undergoes sequential rounds of oxidation to produce acetyl-CoA, NADH, and FADH₂.

Carnitine plays an essential role in fatty acid oxidation by:

Answer: Transporting long-chain fatty acyl groups across the inner mitochondrial membrane

Carnitine shuttles long-chain fatty acyl groups across the inner mitochondrial membrane as acylcarnitine, which is essential because the inner membrane is impermeable to acyl-CoA.

During fatty acid synthesis, malonyl-CoA is formed from acetyl-CoA by which enzyme?

Answer: Acetyl-CoA carboxylase (ACC)

Acetyl-CoA carboxylase (ACC) catalyzes the ATP-dependent carboxylation of acetyl-CoA to malonyl-CoA, the committed step in fatty acid synthesis.

Fatty acid synthesis occurs in which cellular compartment?

Answer: Cytosol

Fatty acid synthesis by fatty acid synthase (FAS) occurs in the cytosol, using NADPH as the reducing agent and malonyl-CoA as the two-carbon donor.

Ketone bodies are produced in the liver primarily from excess:

Answer: Acetyl-CoA

When acetyl-CoA from fatty acid oxidation exceeds the capacity of the TCA cycle (e.g., during fasting), the liver converts excess acetyl-CoA into ketone bodies (acetoacetate, β-hydroxybutyrate, acetone).

Which enzyme is the rate-limiting step in cholesterol biosynthesis?

Answer: HMG-CoA reductase

HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate and is the primary regulated, rate-limiting step in cholesterol synthesis; statins inhibit this enzyme.