Final answer:
Cells maintain high [NaD+]/[NADH] ratio for efficient cellular respiration, while a low [NADP+]/[NADPH] ratio supports biosynthesis and protection against oxidative stress.
Step-by-step explanation:
The question relates to why a cell maintains different ratios for Nicotinamide Adenine Dinucleotide (NAD) versus its phosphorylated form, Nicotinamide Adenine Dinucleotide Phosphate (NADP). The high [NaD+]/[NADH] ratio near 1000 is indicative of the oxidative state required for the electron transport chain in mitochondria to function properly. A high ratio ensures a ready supply of NAD+ to accept electrons, driving cellular respiration and ATP production.
Conversely, the [NADP+]/[NADPH] ratio of about 0.01 is maintained because NADPH acts as a reducing agent, important for biosynthetic reactions and in maintaining the cellular redox state, particularly in defending against oxidative stress.