The small intestine uses segmentation to mix chyme with digestive enzymes, increase its contact with the mucosa, and propel it forward through the digestive tract.

A. 32; 36. Aerobic respiration, including glycolysis, citric acid cycle, and oxidative phosphorylation, can produce up to 36 ATP per glucose. Anaerobic fermentation, however, only produces 2 ATP per glucose, not 36.

B. 32; 2. Aerobic respiration, including glycolysis, citric acid cycle, and oxidative phosphorylation, typically produces up to 36 ATP per glucose, though 32 is a commonly cited figure depending on the specifics of the process. Anaerobic fermentation produces 2 ATP per glucose. The discrepancy in ATP production is due to differences in efficiency and accounting for the energy yield in different conditions.

C. 2; about the same, varying from one tissue to another. Anaerobic fermentation produces 2 ATP per glucose, but aerobic respiration (including glycolysis and subsequent steps) produces up to 36 ATP. The "about the same" part is not accurate for aerobic versus anaerobic processes.

D. 32; none. Anaerobic fermentation does produce ATP, specifically 2 ATP per glucose. Aerobic respiration produces up to 36 ATP per glucose.

E. 36; about the same, varying from one tissue to another. Aerobic respiration can produce up to 36 ATP per glucose, and anaerobic fermentation produces only 2 ATP per glucose. The ATP production difference is significant and not “about the same.”

A. Azotemia is a condition characterized by elevated levels of nitrogenous waste products in the blood, not a direct by-product of protein catabolism.

B. Creatinine is a by-product of muscle metabolism, not directly from protein catabolism.

C. Uric acid is a by-product of nucleic acid metabolism, not protein catabolism.

D. Urea is a primary by-product of protein catabolism, formed in the liver and excreted by the kidneys. This is the correct answer.