Answer: 1. True 2. False 3. True 4. False
Explanation:
1. True NAD+ is a co-enzyme synthesized from Niacin or Nicotinamide, a member of vitamin B complex. NAD+ is an important cofactor in cellular respiration. In the enzyme catalyzed reaction of Glyceraldehyde-3-P dehydrogenase and lactate dehydrogenase, NAD+ is an important cofactor.
2. False. Cofactor and co-enzymes are not irreversible changed. They are reversible. For example in the 5th step of glycolysis, two molecules of NAD+ are reduced to NADH. The conversion of pyruvate to lactate reconvert NADH to NAD+
3. True . Fe, Zn and Mg are enzyme cofactors. Zinc is a cofactor of alcohol dehydrogenase, carboxyl peptidase. Iron is a cofactor of cytochrome oxidase. Magnesium is a cofactor of Hexokinase.
4. False. Cofactors are optimal, and are not optional. Organisms can not function normally without cofactors.
For example when NAD+ is reduced to NADH in glycolysis the availability of NAD+ in the cell is limited. Therefore the absence of a cofactor becomes a bottleneck in the whole reaction process.
