Question

Mention if the following statements are false or true and justify your answer
a. Biotin is required for the activity of fatty acid synthase
b. The reaction of condensation in the synthesis of fatty acids is enhanced by the decarboxylation of malonyl-CoA
c. The synthesis of fatty acids does not depend on ATP
d. Palmitate is the final product of fatty acid synthase
e. All the activities of the enzyme required for the synthesis of fatty acids in mammals are in a single polypeptide chain
f. The fatty acid arachidonate is a precursor of signaling molecules
g. Acetyl-CoA carboxylase is inhibited by citrate.

Answer 1

a) Biotin is required for the activity of fatty acid synthase                   (FALSE)

Biotin is the co-enzyme obtained from vit B7 requires for carboxylation and decarboxylation reaction. Fatty acid synthase does not require biotin for its activity but the enzyme acetyl CoA carboxylase which add CO2 to form malonyl CoA requires biotin. This reaction does not controlled by FAS complex.

b) The reaction of condensation in the synthesis of fatty acids is enhanced by the decarboxylation of malonyl-CoA      (TRUE)

Fatty acid synthase add malonyl coA at the cysteine residue of acyl carrier protein and it removes the CO2 without any help of decarboxylase so this step is not very particular and will increase by rate by the decarboxylation of malonyl-CoA.

c) The synthesis of fatty acids does not depend on ATP                        (FALSE)

Conversion of Acetyl CoA to malonyl CoA requires ATP for energy purpose and this malonyl CoA supplies the two carbon fragments in each cycle so synthesis of fatty acid requires ATP.

d) Palmitate is the final product of fatty acid synthase              (TRUE)

Palmitate it the saturated fatty acid biosynthesized in our body with the help of Fatty acid synthase complex. At the last step the palmitate detached from Fatty acid synthase with the help of thiophorase which is the structural component of Fatty acid synthase.

e) All the activities of the enzyme required for the synthesis of fatty acids in mammals are in a single polypeptide chain    (TRUE)

FAS is the multienzyme complex and dimeric in nature composed of two identical polypeptide chain. Each chain of FAS contains all the enzyme activities of FAS but they are functionally active in dimeric form.

f) The fatty acid arachidonate is a precursor of signaling molecules                                    (TRUE)

Arachidonate is the precursor for prostaglandins which are lipid molecules that help signal inflammation.

g) Acetyl-CoA carboxylase is inhibited by citrate.                            (FALSE)

Citrate promote polymer formation thus increases fatty acid synthesis.

Answer 2

a. False: Biotin is not directly required for the activity of fatty acid synthase. However, biotin is a coenzyme that plays a crucial role in various carboxylation reactions, including those involving acetyl-CoA carboxylase, which is an enzyme involved in fatty acid synthesis.

b. False: The reaction of condensation in the synthesis of fatty acids is enhanced by the decarboxylation of malonyl-CoA. During fatty acid synthesis, malonyl-CoA undergoes decarboxylation, which generates acetyl-CoA and provides the two-carbon unit required for elongation of the fatty acid chain.

c. False: The synthesis of fatty acids requires ATP as an energy source. The initial step of fatty acid synthesis involves the carboxylation of acetyl-CoA to form malonyl-CoA, which consumes one molecule of ATP.

d. True: Palmitate (palmitic acid) is the final product of fatty acid synthase. It is a 16-carbon saturated fatty acid and serves as a common precursor for the synthesis of various other fatty acids.

e. False: The activities of the enzyme required for the synthesis of fatty acids in mammals are not all in a single polypeptide chain. Fatty acid synthase is a large multi-enzyme complex composed of multiple polypeptide chains, each with distinct catalytic functions.

f. True: Arachidonate (arachidonic acid) is a precursor of signaling molecules called eicosanoids. Eicosanoids, such as prostaglandins and leukotrienes, play essential roles in inflammation, immune responses, and other physiological processes.

g. True: Acetyl-CoA carboxylase is indeed inhibited by citrate. Citrate acts as an allosteric inhibitor of acetyl-CoA carboxylase, regulating fatty acid synthesis in response to the energy status of the cell. When citrate levels are high, it indicates that there is sufficient energy available, leading to the inhibition of fatty acid synthesis.