Lipid Metabolism

Lipid Metabolism

Breakdown fats for energy (catabolism)

Build fats for storage/cell functions (anabolism)

What enzymes cleave ester linkages of lipids and phospholipds

Lipases and Phospholipases

How to activate a fatty acid for oxidation:

Form a thioester bond between the carboxyl group of the fatty acid and the thiol group of CoA

Requires 2 ATP

Where does fatty acid activation take place?

The cytosol of the cell

Acyl-CoA can cross through the outer or inner mitochondrial membrane?

Outer mitochondrial membrane

What is attached to Acyl-CoA to help it go through the inner mitochondrial membrane?

Carnitine

What enzyme transfers carnitine onto acyl-CoA?

Carnitine acyltransferase

What is β-oxidation?

β-oxidation is the process of breaking down fatty acids in the mitochondrial matrix to produce acetyl-CoA, NADH, and FADH₂ for energy.

Each round of beta oxidation forms

1 NADH

1 FADH₂

1 or 2 Acetyl-CoA, depending on how many carbons are left

Steps of beta oxidation

1. Oxidation (FADH₂ formed)

2. Hydration

3. Oxidation (NADH formed)

4. Thiolysis (Cuts off 2 C as Acetyl CoA)

How many ATP equivalents are made for each round of beta oxidation?

1 NADH → 3 ATP (through ETC)

+ 1 FADH₂ → 2 ATP (through ETC)

= 5 ATP

What happens to the cleaved off Acetyl-CoA after beta oxidation?

Goes into the TCA cycle

How many ATP can be made from 1 Acetyl-CoA?

1 Acetyl-CoA

= 1 turn of the TCA cycle produces…

3 NADH → 9 ATP (Through ETC)

+ 1 FADH₂ → 2 ATP (Through ETC)

+ 1 ATP

= 12 ATP

How many ATP can be produced from 12 C Lauric acid?

(5 rounds of beta oxidation x 5 ATP per round) + (6 Acetyl-CoA produced x 12 ATP per Acetyl-CoA) - 2 ATP from investment = 95 ATP

What happens when the body produces too much Acetyl-CoA?

Excess acetyl-CoA is converted to ketone bodies

The Ketone Bodies

Acetoacetate

Beta Hydroxybutyrate

Acetone

Ketogenesis

Production of ketone bodies

Ketogenesis prevents _______________

The TCA from being overwhelmed

Ketosis

Abnormally high blood ketone bodies

When does ketosis occur?

Starvation

Low Carb/High Protein Diet

Uncontrolled diabetes mellitus

Ketones are ______ so they ______ blood pH

acidic; lower

Response to ketoacidosis

Hyperventilating → Releases CO₂ → Raise blood pH

Can think of ketone bodies as ______

Warning signals that the body is switching energy sources from sugars to fats

Fatty Acid Biosynthesis

Body builds fatty acid from acetyl-CoA when energy is high and there is not much need for energy production (TCA)

Where does fatty acid biosynthesis take place?

The cytosol

Is fatty acid biosynthesis a linear, spiral, or cyclic pathway?

spiral pathway