2. Succinate dehydrogenase normally catalyses the conversion of succinate to fum

Question

2. Succinate dehydrogenase normally catalyses the conversion of succinate to fumarate. If malic acid is added to this reaction, fumarate is no longer produced. Identify the enzyme, product, substrate, and inhibitor in this reaction. 3. A chemical reaction will proceed twice as fast for every 10°C rise in temperature. However, a reaction catalyzed by an enzyme will speed up only to a certain temperature at which point the reaction will cease. How do you explain this observation? 4. L-amino acid dehydrogenase is an enzyme that can catalyze the oxidation of different L-amino acids. It cannot catalyze the oxidation of D-amino acids or other L-compounds. This enzyme is very for its substrate.

Explanation / Answer

2. The enzyme is succinate dehydrogenase. Its substrate is succinate, which is converted into fumarate (the product). Malic acid is a structural analogue of succinate. It can bind to the active site of the enzyme without being converted into the product, and hence, competes with succinate, the usual substrate. Therefore, succinate dehydrogenase with is bound to malate can neither act on it nor can lose it. The enzyme site thus emains blocked. Adding excess of succinic acid can remove the inhibition.

3. In order to react, molecules must collide and come close to each other. The collisions must be sufficiently energetic to break chemical bonds, this is known as activation energy. With an increase in temperature, the molecules move faster and collide more vigorously, greatly increasing the likelihood that the reaction occurs. Therefore, the kinetic energy of the molecules increases with an increase in temperature, and thus, enhances the reaction.

However, in case of enzymes, with a gradual increase in temperature, there is an initial increase in rate of chemical reaction. After certain temperatures, the enzyme denature and lose their structural hierarchy above the secondary structure level. Therefore, they are no more functional.

It can be concluded that loss of function of enzymes with increasing temperature is due to loss of secondary structure or denaturation of the enzymes.

4. Specific

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