Which food likely has the fewest calories per gram of serving and why? a) grape jelly because it's mostly simple sugars. b) peanut butter because it contains plant-based fats. c) whole milk because most of the animal fat remains. d) bread because it contains a combination of complex carbohydrates, simply sugars and plant-based fats.

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.

the denominator has a very specific role.