Cells use a large amount of energy replicating DNA. Even more energy is used to check that each new DNA strand is an exact copy before it replicates again. Why is the exact replication of DNA important to cells?

DNA replication plays an important role in the growth and renewal of cells. Growing organisms are constantly creating new cells as they develop into a larger body. And over time, some cells can become damaged, grow old, or die.

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.

a symbiotic relationship with the mitochondria