Respiration in Plants

All the given mechanisms in options leads to ATP formation. The type of method used depends on the type of organism and their energy transfer mechanisms.

$\bullet$ Photophosphorylation is the enzymatic formation of ATP from ADP coupled to the light dependent transfer of electrons in photosynthetic cells.

$\bullet$ Substrate level phosphorylation is the phosphorylation of ADP or some other nucleoside 5-diphosphate coupled to the dehydrogenation of an organic substrate, independent of the electron transfer chain.

$\bullet$ Oxidative phosphorylation is the enzymatic phosphorylation of ADP to ATP coupled to electron transfer from a substrate to molecular oxygen.

If mitochondria is absent in mature RBC then the source of energy for cell will be glycolysis. Mature mammalian RBC lack nucleus, mitochondria and other cell organelles in order to increase their oxygen carrying capacity. In such case, they cannot use none of the oxygen they transport for their own energy requirements. Thus, they use glycolysis and lactic acid fermentation as a source of energy.

Both assertion and reason are true and reason is correct explanation of assertion.

Respiratory pathway is considered as an amphibolic pathway as it involves both anabolic and catabolic reactions. For example, fatty acids are broken down to acetyl Co-A before entering respiratory pathway and many other carbonic acids are synthesised as an intermediate compounds.

The final stage of respiratory chain involves cytochrome oxidase, which contains copper. This stage can be specifically inhibited by cyanide or carbon monoxide. Cyanide combines with the copper and prevents oxygen from combining with it.

Glucose is converted into two molecules of pyruvic acid so, two cycles of Krebs’ cycle occur for one per glucose molecule. Each turn of Krebs’ cycle produces 3 NADH, 1 FADH$_2$ and 1 ATP molecule. On oxidation, NADH produces 3 ATP molecules and 1 FADH$_2$, which in turn produces 2 ATP molecules. Thus, in each turn of Krebs’ cycle 12 ATP molecules are produced. Two Krebs’ cycles occur per glucose molecule because glycolysis results in the formation of 2 pyruvic acid molecules by glucose breakdown.