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Biochemistry

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Enzymes

Question
71 out of 79
 

Lipid peroxidation as a cause of ageing and injury of cells is



A Free radical theory

B Apoptosis theory

C Enzyme cascade theory

D Cell destruction theory

Ans. A Free Radicals theory

Lipid peroxidation is a source of free Radicals:

a. Peroxidation (Atuo-oxidation) of lipids exposed to O2 is responsible for:-

i. Detrition of foods (Rancidity)

ii. Damage to tissues in vivo, where it may be a cause of cancer, inflammatory disease, atherosclerosis, aging etc.

iii. The deleterious effects are caused by free Radicals — eg. ROO°, RU°, OH° - produced during peroxide formation from fatty acids containing methylene-interrupted bonds (poly unsaturated F.A.)

b. Antioxidants: - control and reduce Lipid Peroxidation — eg.

i. Propyl glycol, Butylated hydroxyanisole and Butylated hydroxytoluene — used as food additives

ii. Vit. E (Tocopherol) — Naturally occurring Antioxidant

iii. Vit. C and Urate Naturally occurring antioxidant

A. Betacarotene -4 an anti oxidant at Low PH

B. Lipid peroxidation is a chain reaction.

Antioxidants are two types according mode of action:

a. Preventive antioxidants (=reduce the rate of chain initiation): eg.

i. catalase

ii. other peroxidases

iii. chelators of metal ions - EDTA and DTPA

iv. Endogenous ceruloplasmin

b. Chain breaking antioxidants (=interfere with chain propagation): eg.

i. Superoxide dismutase

ii. Urate

iii. Vit-E

iv. Phenols or aromatic amines

v. Se-containing glutathione peroxidases.

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