Proteins are absorbed primarily in the form of:

Correct Answer: C

Rationale: The correct answer is C: amino acids. Proteins are broken down by digestive enzymes into amino acids before being absorbed in the small intestine. Amino acids are the building blocks of proteins and are the form in which they are primarily absorbed. Choice A (fatty acids) is incorrect as fatty acids are the end products of fat digestion, not protein digestion. Choice B (disaccharides) is incorrect because disaccharides are sugars that are broken down into monosaccharides, not proteins. Choice D (polypeptides) is incorrect as proteins are broken down into amino acids and not absorbed as polypeptides.

Correct Answer: D

Rationale: The correct answer is D, rennin. Rennin is the enzyme in infants responsible for coagulating milk, which aids in the digestion process. Choice A, casein, is a milk protein and not an enzyme. Choices B and C, pepsinogen and trypsin, are digestive enzymes but are not specifically involved in coagulating milk in infants.

Correct Answer: D

Rationale: The correct answer is D: By enterokinase. Trypsin is activated by enterokinase, an enzyme secreted by the small intestine. Enterokinase plays a crucial role in converting trypsinogen into its active form, trypsin. Choices A, B, and C are incorrect because trypsin is specifically activated by enterokinase, not by zymogen, bile, or gastrin.

Correct Answer: C

Rationale: Chymotrypsin is an enzyme found in pancreatic secretions that plays a role in protein digestion. Rennin is primarily found in the stomach and is involved in milk digestion. Pepsin is also a stomach enzyme that aids in protein breakdown. Casein is a protein found in milk, not an enzyme involved in pancreatic secretions. Therefore, the correct answer is Chymotrypsin.

Correct Answer: A

Rationale: Albumin is the correct answer. It is a plasma protein that helps maintain osmotic pressure, thereby playing a vital role in regulating fluid balance in the body. Fibrinogen is involved in blood clotting, not fluid balance. Hemoglobin is responsible for oxygen transport in red blood cells, not fluid balance. Collagen is a structural protein found in connective tissues, not directly involved in fluid balance.