There will be no effect of the rate of the reaction. The rate of the catalyzed r

Question

There will be no effect of the rate of the reaction. The rate of the catalyzed reaction will double for all concentrations of substrate. In animals, if the fuel consumed exceeds energy expended, fats are synthesized from carbohydrates in order to store the excess energy. Acetyl-coA Carboxylase catalyzes the first dedicated step in fatty acid synthesis. This enzyme responds to a large number of cellular signals. A logical strategy for the regulation of Acetyl-coA Carboxylase might include: Activation when concentration of AMP is high vs. the concentration of ATP Activation when concentration of AMP is low vs. the concentration of ATP. Inhibition when the concentration of AMP is low vs. the concentration of ATP. Inhibition by insulin, reflecting high levels levels of glucose Both c and d Methanogens used to be one of the dominant life forms on Earth. Today their growth is restricted to very specialized environments. This is because they:

Explanation / Answer

Ans. Acetyl-CoA + HCO3- -----Acetyl-CoA Carboxylase ------> Malonyl-CoA

Focus on following two statements-

I. Fats are synthesized from carbohydrates (excess intake).

II. Acetyl-CoA Carboxylase catalyzes the first step in fatty acid biosynthesis.

The statement indicates that excess intake of carbohydrates leads to lipid biosynthesis.

Carbohydrates (Glucose, starch, glycogen, etc.) are the immediate source of metabolic energy (ATP). There is relatively higher [ATP] when dietary carbohydrates are taken in excess.

Note that there is a limited pool of ATP, ADP and AMP in varying concentrations in the cell. Say, there is 200 mM of all the three forms. There is no formation of additional ATP or its loss- the forms only interconvert depending on the energy supply to the cell.

That is, [ATP] is relatively high, and [ADP] and [AMP] are low in a cell with surplus energy sources when compared to the same with a cell with deprived energy source.

So, when excess carbohydrate is taken, there is higher [ATP] and lower [AMP] than normal; or relatively lower [AMP] and higher [ATP] act as a signal to indicate excess of available energy sources in the cell.

The relatively lower [AMP] acts as activator for the enzyme Acetyl-CoA carboxylase (ACC)- that informs the enzyme that there is excess energy source (carbohydrates) in the cell. So, the activated ACC initiates fatty acid biosynthesis.

Therefore, correct option is B. Activation --- [AMP] is LOW

#A. Incorrect. A higher [AMP] indicates that there is scarcity of cellular energy because it forms when available ATP is consumed up during cellular processes.

#C. Incorrect. Lower [AMP] activates ACC. See #B

#D. Incorrect. Inhibition of insulin would result “no glucose uptake” by the cell. It would further deprive the cell off glucose, and ATP in turn. So, in such case, [AMP] would be low.

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