Fatty Acid Oxidation

What is the first stage of using fat for energy?

Fat mobilization from fat cells (adipose tissue)

What is the second stage?

Activation of fatty acids (turning them into fatty acyl-CoA)

What is the third stage?

Fatty acid breakdown (β-oxidation) in mitochondria → acetyl-CoA → energy

Which hormones trigger fat breakdown?

Glucagon and epinephrine

What enzyme breaks down triglycerides?

Hormone-sensitive lipase (HSL)

What are the products of triglyceride breakdown?

Free fatty acids (FFA) and glycerol

What happens to glycerol?

Becomes DHAP → enters glycolysis or gluconeogenesis

How are fatty acids activated?

Fatty acid + CoA + ATP → fatty acyl-CoA

Where does activation happen?

Cytosol (long-chain fatty acids)

Where does β-oxidation happen?

Mitochondrial matrix

How do long-chain fatty acids enter mitochondria?

Via carnitine shuttle

How do short/medium-chain fatty acids enter mitochondria?

They diffuse freely; no carnitine needed

What happens if carnitine is missing?

Long-chain fatty acids cannot enter mitochondria → less energy

Step 1 of β-oxidation: Oxidation → enzyme?

Acyl-CoA dehydrogenase → FADH₂ formed

Step 2 of β-oxidation: Hydration → enzyme?

Enoyl-CoA hydratase → adds water

Step 3 of β-oxidation: Oxidation → enzyme?

Hydroxyacyl-CoA dehydrogenase → NADH formed

Step 4 of β-oxidation: Thiolysis → enzyme?

β-ketothiolase → acetyl-CoA released, shortens fatty acid

What's similar to TCA cycle chemistry?

Sequential oxidation of carbon, producing NADH/FADH₂

Can fatty acids make glucose?

No - acetyl-CoA cannot go back to glucose

Why do we need carbs for fat burning?

Carbs provide oxaloacetate for TCA cycle → efficient energy from fats

How to calculate ATP from a saturated fatty acid?

Count FADH₂ + NADH from β-oxidation cycles + ATP from acetyl-CoA in TCA cycle, minus 2 ATP for activation

When are ketone bodies made?

Starvation, fasting, or diabetes → high fat breakdown, low carbs

Where are ketone bodies made?

Liver mitochondria

Main ketone body process?

Acetyl-CoA → acetoacetate → β-hydroxybutyrate & acetone

Why do tissues use ketone bodies?

Alternative fuel → converted to acetyl-CoA → TCA cycle

Name the 3 ketone bodies.

Acetoacetate, β-hydroxybutyrate, acetone

What is diabetic ketoacidosis?

Too many ketone bodies → blood pH drops → metabolic acidosis

Consequences of ketoacidosis?

Dehydration, electrolyte imbalance, potentially life-threatening