Fatty acid synthesis: MCQ of the day

Q) In what compartment does the de novo fatty acid synthesis occurs?

a) Mitochondria
b) Perioxosome
c) Endoplasmic reticulum
d) Cytosol

Explanation
Fatty acid biosynthesis takes place in the cytosol
Intermediates covalently linked to an acyl carrier protein
The acetyl CoA is activated to malonyl CoA
Four steps repeating cycle are condensation, reduction, dehydration, and reduction. One cycle leads to extension by 2-carbons

Comparison of Fatty acid synthesis and oxidation

Characteristics	Synthesis	Degradation
Location	Cytosol	Mitochondrial Matrix
Activated Intermediates	Bound to ACP	Thioester of CoA
Enzymes	FAS is a multienzyme complex	4 distinct enzymes
Substrate	Acetly CoA	Fatty Acids
Direction	Starts at methyl end	Starts at the carboxyl end
Cofactors	NADPH	FADH/NADH
Major sites	Liver	Muscle and Liver
Hormonal Regulation	High Insulin/Glucagon ratio	Low Insulin/Glucagon ratio
Activator	Citrate	Free fatty acids
Inhibitor	Fatty acyl CoA	Malonyl CoA