Correct Answer: A

Rationale: The correct answer is A: carbohydrates. Photosynthesis is the process by which plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy stored in glucose (a type of carbohydrate). This glucose is used by the organisms for energy production and as a building block for other organic compounds. Choice B, proteins, is incorrect because proteins are synthesized through a different process involving amino acids. Choice C, fats, are not directly synthesized through photosynthesis; they are typically formed from excess carbohydrates. Choice D, vitamins, are organic compounds that are required in small amounts for various physiological functions but are not directly synthesized through photosynthesis.

Correct Answer: A

Rationale: The most likely nutrition-related side effect after head and neck surgery for cancer treatment is aspiration. This is due to changes in swallowing mechanics, which can cause food or liquids to be inhaled into the lungs. While acid reflux, dumping syndrome, and diarrhea are potential side effects related to nutrition, they are not as directly connected to head and neck surgery. Acid reflux is more often related to issues with the lower esophageal sphincter, dumping syndrome is typically a complication of gastric surgery, and diarrhea can have various causes, including certain medications or gastrointestinal illnesses.

Correct Answer: A

Rationale: The correct answer is A: vitamin B12. Intrinsic factor is a glycoprotein produced by the stomach that is necessary for the absorption of vitamin B12 in the small intestine. Vitamin B12 binds to intrinsic factor in the stomach, forming a complex that is then absorbed in the ileum. This absorption process is crucial for preventing vitamin B12 deficiency. Choices B, C, and D are incorrect because they do not require intrinsic factor for absorption. Folate is absorbed in the small intestine through a different mechanism, niacin can be absorbed in the small intestine without the need for intrinsic factor, and vitamin B6 does not rely on intrinsic factor for absorption.

Correct Answer: B

Rationale: The correct answer is B. The classification of the 20 common amino acids is not based on the properties of their side chains, but rather on the structure of their amino and carboxyl groups. These groups are consistent among all amino acids, while the side chains, also known as R groups, are what vary and give each amino acid its unique properties. Choice A is correct because proteins are indeed composed of amino acids. Choice C is incorrect because while the side chains of amino acids can vary, the general structure of an amino acid - a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a side chain - is consistent. Choice D is correct because amino acids do polymerize to form long chains called polypeptides, which can then fold into complex shapes to form proteins.

Correct Answer: D

Rationale: Trypsin and chymotrypsin are enzymes involved in protein digestion. These enzymes are secreted by the pancreas, not the small intestine, liver, or stomach. The pancreas plays a crucial role in producing digestive enzymes that aid in breaking down proteins in the small intestine. The small intestine is the site where these enzymes act, not where they are secreted. The liver is responsible for producing bile, not digestive enzymes. The stomach secretes gastric juices but not trypsin and chymotrypsin. Therefore, the correct answer is the pancreas.