Enormous energy reserves because its stored in  the reduced

form and anhydrous (very non-polar). Oxidation produces 9 kcal / g.

In mammals the main site of TAG reserved is cytoplasm adipose (fat cells). Adipose cells specially for

the synthesis, storage and mobilization of TAG into fuel molecules to be transferred

to other tissues by the blood

First Stage TAG hydrolysis by Lipase

TAG + 3 H2O   (lipase)   Glycerol + FA

Lipase activity of adipose cells is regulated by several hormones

Epinephrin, norephineprin, glucagon, adrenocorticotropic hormone is to

induce lipolysis

Digestion - Hydrolysis Reaction

Knoop (1904): Fatty acids are broken down by release 2carbon unit in every stage

Fatty acids are broken down by beta oxidation to carbon  beta

oxidationFatty acid oxidation in mitochondria

Fatty acid activation is required before entering the mitochondrial matrix

In the outer membrane of mitochondria and is catalyzed by enzyme acyl CoA synthetase (fatty acid tiokinase)

ATP stimulate the formatio n of thioester bond formation between the carboxyl group

of sulf hidril FA with the CoA:

R-COO + ATP R-COO-AMP (adenylate acyl) + PPi

Adenylate acyl + HS-CoA    R-COO-S-CoA (acyl-CoA)

PPI pirofosfatase hydrolyzed by the reaction becomesirrev to the right

R-COO + CoA + ATP  R-COO-S-CoA (acyl CoA) + AMP + 2 Pi + 2H

Initial Step: Requires an ATP to synthesize acetyl CoA with the fatty acid.

FA activated in outside the mitochondria, whereas oxidation in the

mitochondria Long-chain acyl

CoA (active) can not transferred into the inner mitochondrial membrane 

 need special transport mechanism  conjugated with carnitine

Carnitine: zwitter ions formed from lysine catalyst:

carnitine acyl transferase I (bound to the outer mitochondrial membrane)

Why beta-oxidation?

Alfa oxidation In the seeds of plants that are sprouting.

COOH group is released as CO2C-alpha-oxidised  aldehyde 

 further oxidation by NAD +  COOH group Omega oxidation

In the hearts of several animal tissuesTG acid omega oxidation of alpha, omega-

dicarboxylic Beta oxidation

Fatty acids are the primary fuel for humans and mammals

Fatty acids catabolyzed by O2 to CO2 and H2O

40% of the free energy produced by the cells preserved for forming ATP, 

the remaining energy is released as heat

Catabolism of fatty acids occurs in mitochondria through a process known as beta oxidation

The process of fatty acid oxidation (after activated to form acyl CoA)

Takes place in mitochondria

Four  reactions stages:

1.Oxidation (dehydrogenation) by FAD2. Hydration

3. Oxidation by NAD

4. Tiolisis by CoA

  The four reactions stages, will shorten the two carbon atoms in the acylchains and formed  FADH2, NADH and acetyl CoA

20

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• Contribute to the formation of double chains of atoms C2 - C3.

• Has a hydrogen acceptor FAD+.

• Between the different fatty acids in length  different enzyme

•Catalyzes the hydration of trans enoyl CoA

•The addition of a hydroxyl group at C no. 3

•Enzyme is stereospecific•Generate 3-L-

hidroksiasil Co. A

•Catalyzes the oxidation of-OH at C no. 3 / C β  into a ketone

•Electron acceptor:  NAD+

• Splitting of carbon atoms between C alpha and C beta

• β-Ketotiolase   catalyze thioester bond breaking.

• Acetyl-CoA   removed and the remaining fatty acid acyl co A is connected with tio cysteine  via thioester bonds.

HSCoA replace cysteine  thiol thiols, generating fatty acyl-CoA (whichhave been reduced by 2 C).

ExamplesBeta oxidation of Myristic Acid

To be continued withFinal Exam of

Fatty Acid Catabolism