Question

A cell can carry out its constant and intensive metabolic activities with relatively small amounts of such vital components as ATP, $NA{D}^{+}$ , coenzyme A, etc. because it can

• A. rapidly recycle these compounds
• B. bypass reactions that require these compounds
• C. incur an oxygen debt until these compounds become available
• D. utilize substitute molecules in place of these compounds

Answer 1

The correct option is A rapidly recycle these compounds

• ATP as we know is the energy currency of a cell; the phosphate bond that is present in the ATP when broken releases large amount of energy which can be used by the cell.
• After the ATP molecule has released energy it will give break down to ADP and P which will be released in the cytoplasm or the matrix of organelles where it is used.
• These ADP and P are used as subtrates when the ATP is to be generated again by the cell by the reactions such as glycolysis, kerb cycle, chemiosmotic phosphorylation.
• NAD is an electron acceptor that accepts electrons that are released from the glycolysis reaction and also during the kerb cycle.
• After they have accepted the electron they transfer the electron to the electron transfer chain that are transported through various complexs in the chain and produce energy.
• The NADH is transformed to NAD again and is ready to be used again.
• CoA that is used for the formation of acetyl CoA from the pyruvate is also regenerated in the kerb cycle and released in the cytoplasm so that it can again be used to decarboxylate pyruvic acid and used for the oxidation of fatty acid.
• Therefore even if small amount of these componets are present in the cell the cell can carry out its metabolic activities as these components after being used are regenerated again and ready to be used o no hinderance occurs in the pathway of metabolism.
• Therefore the answer 'rapidly recycle these compounds' is correct.