Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 1General Principles & Energy Production in Medical Physiology 25

FIGURE 1–26 Fatty acid oxidation. This process, splitting off two carbon fragments at a time, is repeated to the end of the chain.

FIGURE 1–27 Formation and metabolism of ketone bodies. Note the two pathways for the formation of acetoacetate.

OH+ HS-CoA

——

OH

H α,β-Unsaturated fatty acid –CoA

β-Keto fatty acid –CoA

β-Hydroxy fatty acid –CoA

"Active" fatty acid + Acetyl –CoA

——

C

O

H 2 O+ R

——

O

CH 2 CH 2 CH 2 CH 2

S

R

CoA+ HS-CoA

——

C CS

O

——

O

R CH 2 CoA

——

C S CoA + CH 3 CS

O

——

O

R

——

C

O

R C CH 2

Mg^2 +

ATP ADP

Fatty acid

Oxidized

flavoprotein

Reduced

flavoprotein

"Active" fatty acid

C S CoA

H 2 O+ R

——

O

CoA CH CH C S CoA

NAD+ NADH+ H+

R = Rest of fatty acid chain.

S

——

C

O

CH 3 CoA+ CH 3 S

——

C

O

CoA

2 Acetyl-CoA Acetoacetyl-CoA

——

C

O

CH 3 CH 2 S

——

C

O

CoA+ HS-CoA

β-Ketothiolase

CH 3 C CH 2 SC CoA+ H 2 O

Acetoacetyl-CoA

Acetyl-CoA+ Acetoacetyl-CoA

HMG-CoA Acetoacetate+ H++ Acetyl-CoA

Acetoacetate

Acetoacetate

Acetone

3-Hydroxy-3-methylglutaryl-CoA

(HMG-CoA)

β-Hydroxybutyrate

CH 2

—

C

OH

CH 3

CH 2

C S CoA + H+

CH 2

–CO 2

CH 3 C C O− CO 2 + ATP

CH 3 C CH 3

+ H+

CH 3 CHOH CH 2 O−

——

C

O

+ H+

CH 3 C CH 2 C O−

COO−

+ H++ HS-CoA

Deacylase

(liver only)

+2H –2H

Tissues except liver

——

O

——

O

——

O

——

O

——

O

——

O

——

O

——

O