Biochem Quiz 7

Fats From Diet (Seven Steps)

1. Fats ingested in the diet

2. Bile salts emulsify dietary fats in small intestine

3. Lipases degrade TAGs

4. FFAs taken up by intestinal mucosa and converted to TAGs

5. TAGs incorporated into chylomicrons

6. Chylomicrons move through bloodstream and target tissues

7. Lipoprotein lipases interact with chylomicrons and convert TAGs to FFAs

Stored Fats (Steps 1 and 2)

1. Adipocytes with oil droplets are 90% TAGs

2. Lipolysis initiated when glucagon binds to Gs-coupled GPCR in adipocytes

Stored Fats Step Three

a. Triacylglycerol → Diacylglycerol and FFA via ATGL

b. Diacylglycerol → Monacylglycerol and FFA via HSL

c. Monacylglycerol → glycerol and FFA via MGL

FF

Serum Albumin transports FA through blood

FFA Activation and Transport Step 2

FA transported into cell via facilitated diffusion transporter

FFA Activation and Transport Step 3

FA → Fatty Acyl CoA via Fatty CoA Synthetase

FFA Activation and Transport Step 4

Fatty Acy CoA + Carnitine → Fatty Acyl Carnitine via CPT1

FFA Activation and Transport Step 5

Fatty Acyl Carnitine transported into mitochondria

FFA Activation and Transport Step 6

Fatty Acyl Carnitine → Fatty Acyl CoA via CPT2 in mitochondria

Beta Oxidation Step 1

• Oxidation of aplha-beta bond

• Enzyme: Acyl CoA Dehydrogenase

• FAD reduced to FADH2

• FADH2 goes to ETC

Beta Oxidation Step 2

• Hydration

• Enzyme: Enoyl CoA Hydratase

• Hydroxyl group on beta carbon

Beta Oxidation Step 3

• Oxidation

• Enzyme: Beta-Hydroxylacyl CoA Dehydrogenase

• NAD+ reduced to NADH

• NADH to ETC

• Beta carbon is a carbonyl group now

Beta Oxidation Step 4

• Cleavage

• Enzyme: Acyl CoA Acetyltransferase (thiolase)

• Adding coASH

• Release of acetyl coA (2 carbons)

• Original Beta carbon now carbon #1 (carbonyl carbon)

Three Ketone Bodies

1. Acetone

2. Acetoacetate

3. Beta-Hydroxybutarate

When does the body make ketone bodies and why?

• In liver

• Used by extra-hepatic tissue

• After B-oxidation liver cannot use acetyl coA

Step 1 Ketogenesis

• Reactant: 2 Acetyl CoA

• Enzyme: Thiolase

• Product: Acetoacetyl CoA

Step 2 Ketogenesis

• Reactant: Acetoacetyl CoA

• Enzyme: HMG-CoA Synthase

• Product: HMG-CoA

• Add third acetyl CoA

Step 3 Ketogenesis

• Reactant: HMG-CoA

• Enzyme: HMG-CoA Lyase

• Product: Acetoacetate

• One acetyl CoA leaves

Step 4 Ketogenesis - To create Acetone

• Reactant: HMG-CoA

• Enzyme: Acetoacetate Dehydrogenase

• Acetone

• Decarboxylation

• Released via exhalation

Step 4 Ketogenesis - To create B-Hydroxybutyrate Dehydrogenase

• Reactant: Acetoacetate

• Enzyme: B-Hydroxybutyrate Dehydrogenase

• Product: B-Hydroxybutarate

• NADH oxidized to NAD+

Ketone Oxidation Step 1

• Reactant: B-Hydroxybutyrate

• Enzyme: B-Hydroxybutyrate Dehydrogenase

• Product: Acetoacetate

• NAD+ reduced to NADH

Ketone Oxidation Step 2

• Reactant: Acetoacetate

• Enzyme: B-Ketoacyl CoA Transferase

• Succinyl CoA to Succinate

• Product: Acetoacetyl CoA

Ketone Oxidation Step 3

• Reactant: Acetoacetyl CoA

• Enzyme: Thiolase

• Product: 2 acetyl CoAs

• Addition of CoASH