fatty acid synthesis

step 1

transfer acetyl CoA from matrix → cytosol

1. acetyl CoA combines w/ oxaloacetate → citrate in mito.

2. citrate transferred (w/ citrate transporter) from mito. → cytosol

3. citrate cleaved by ATP-citrate lyase to produce acetyl CoA + oxaloacetate (reverse #1)

step 2

some of acetyl CoA converted to malonyl CoA w/ enzyme Acetyl CoA carboxylase:

• Biotin-enzyme + ATP + HCO3 (carboxybiotin) → (reversible) CO2-biotin + ADP + Pi + H+

• CO2-biotin + Acetyl CoA → Malonyl CoA + Biotin-enzyme

step 3

each acetyl and malonyl CoA is attachedto an acyl carrier protein to produce acetyl and malonyl ACP (each)

1. Acetyl CoA + ACP → Acetyl ACP + CoA
   (enz: Acetyl transacylase)

2. Malonyl CoA + ACP → Malonyl ACP + CoA
   (enz: malonyl transacylase)

step 4

condensation: Acetyl ACP + Malonyl ACP → Acetoacetyl ACP + ACP + CO2

enz: b-ketoacyl synthase

step 5

reduction: Acetoacetyl ACP + NADPH → D-3-Hydroxybutyryl ACP + NADP⁺

enz: b-ketoacyl reductase

step 6

dehydration: D-3-Hydroxybutyryl ACP → Crotonyl ACP + H2O

enz: 3-Hydroxyacyl dehydratase

step 7

reduction: Crotonyl ACP + NADPH → Butyryl ACP + NADP⁺

enz: Enoyl reductase

effect of double bonds in fatty acid atp synthesis

every C=C LOSES one FADH2