Multiple choice questions on Fatty acid synthesis: Biochemistry

                          Multiple choice questions on Fatty acid synthesis

1. In what compartment does the de novo fatty acid synthesis occurs?
a) Endoplasmic reticulum
b) Cytosol
c) Mitochondria
d) Perioxosome

2. Which of the following molecules serves as the precursor for fatty acid synthesis?

a) Acetyl-CoA

b) Glucose

c) Malonyl-CoA

d) Pyruvate

3. The enzyme responsible for the commitment step in fatty acid synthesis is:

a) Acetyl-CoA carboxylase (ACC)

b) Fatty acid synthase (FAS)

c) Hormone-sensitive lipase

d) Malonyl-CoA decarboxylase

4. During fatty acid synthesis, malonyl-CoA is added to the growing fatty acid chain by the enzyme:

a) Acetyl-CoA carboxylase (ACC)

b) Acyl-CoA dehydrogenase

c) Fatty acid synthase (FAS)

d) Lipoprotein lipase

5. What is the reducing agent used in the fatty acid synthesis pathway?

a) FAD+

b) FADH2

c) NAD+

d) NADH

6. Which hormone promotes the activation of acetyl-CoA carboxylase, thereby enhancing fatty acid synthesis? 

a) Glucagon

b) Epinephrine  

c) Insulin 

d) Cortisol

7. The end product of a complete fatty acid synthesis cycle is: 

a) Acetyl-CoA

b) Lactic acid 

c) Malonyl-CoA

d) Palmitic acid (16-carbon fatty acid) 

Answers:

1. b) Cytosol, Fatty acid biosynthesis takes place in the cytosol

2. a) Acetyl-CoA

3. a) Acetyl-CoA carboxylase (ACC)

4. c) Fatty acid synthase (FAS)

5. d) NADH

6. c) Insulin

7. d) Palmitic acid (16-carbon fatty acid) 

Explanation:
Intermediates covalently linked to an acyl carrier protein. The acetyl CoA is activated to malonyl CoA.
The 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	Acetyl 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