Fatty Acid Metabolism: Key Concepts in Lipolysis, β-Oxidation, and Ketone Bodies

What are fatty acids stored as in adipose tissue?

Triacylglycerols (TAGs)

What is the first stage of fatty acid use?

Lipolysis

What does TAG break down into during lipolysis?

Fatty acids and glycerol

What is the role of carnitine in fatty acid metabolism?

It transports fatty acyl-CoA into mitochondria.

What enzyme activates fatty acids?

Acyl-CoA synthetase (thiokinase)

What is produced during β-oxidation?

Acetyl-CoA

What is the energy yield from complete oxidation of palmitate (C16)?

106 ATP

What happens to glycerol after lipolysis?

It is converted into glycolytic intermediates in the liver.

What is the final product of odd-chain fatty acid metabolism?

Propionyl-CoA

What two important enzymes are required for odd-chain fatty acid metabolism?

Propionyl-CoA carboxylase (requires biotin) and Methylmalonyl-CoA mutase (requires vitamin B12)

What are the three types of ketone bodies produced in the liver?

Acetoacetate, β-hydroxybutyrate, and acetone

When are ketone bodies used as fuel?

During fasting, starvation, and untreated diabetes

What is the first step in the carnitine shuttle?

Carnitine acyltransferase I (CAT I) transfers fatty acid to carnitine.

What does β-oxidation consist of?

A repeating 4-step cycle: oxidation, hydration, oxidation, and thiolysis.

What is the role of enoyl-CoA isomerase in fatty acid metabolism?

It helps process unsaturated fatty acids during β-oxidation.

What does the process of thiolysis in β-oxidation release?

Acetyl-CoA

What is the intermediate formed during fatty acid activation?

Acyl adenylate

What enzyme hydrolyzes PPi to make fatty acid activation irreversible?

Pyrophosphatase

What is the function of translocase in the carnitine shuttle?

It moves acyl-carnitine into mitochondria.

What are the products of β-oxidation besides acetyl-CoA?

NADH and FADH₂