Lipid Metabolism

What hormone triggers mobilization of stored triacylglycerols?

Glucagon (and epinephrine) – signal energy need.

What is the role of hormone-sensitive lipase?

Hydrolyzes triacylglycerols in adipose tissue, releasing fatty acids.

What molecule transports fatty acids in blood?

Serum albumin.

What enzyme activates fatty acids before oxidation?

Fatty acyl-CoA synthetase.

How are long-chain fatty acids transported into mitochondria?

Via the carnitine shuttle.

What molecule inhibits carnitine acyltransferase I?

Malonyl-CoA.

What coenzymes are used in β-oxidation?

FAD and NAD⁺ (producing FADH₂ and NADH).

What are the 4 recurring steps in β-oxidation?

Oxidation, hydration, oxidation, thiolysis (OHOT).

What happens to odd-chain fatty acids?

They form propionyl-CoA, which is converted to succinyl-CoA (requires B12).

When are ketone bodies produced?

During starvation or diabetes, when oxaloacetate is low.

What is the first committed step in fatty acid synthesis?

Formation of malonyl-CoA by acetyl-CoA carboxylase (ACC).

What cofactor is used by ACC?

Biotin.

What are the four steps in fatty acid synthesis?

Condensation, reduction, dehydration, reduction (CRDR).

What is the role of Acyl Carrier Protein (ACP)?

Carries growing fatty acid chain; has phosphopantetheine prosthetic group.

How is fatty acid synthesis regulated?

Insulin activates ACC (stimulates synthesis); glucagon inhibits it (via PKA).

What is the final product of de novo synthesis in animals?

Palmitate (16:0).

Where does fatty acid synthesis occur in animals?

Cytosol.

Where does fatty acid oxidation occur?

Mitochondria.

What is the mnemonic for β-oxidation steps?

OHOT: Oxidize, Hydrate, Oxidize, Thiolysis.

What is the mnemonic for fatty acid synthesis steps?

CRDR: Condense, Reduce, Dehydrate, Reduce.

What is the mnemonic for fat transport into mitochondria?

CAR: Carnitine, Acyltransferases, Regulation by malonyl-CoA.