Calcium is actively absorbed by the small intestine and this is accelerated by

Correct Answer: C

Rationale: The correct answer is C: Vitamin D. Vitamin D plays a crucial role in enhancing the absorption of calcium in the small intestine by promoting the synthesis of calcium-binding proteins. This process ensures adequate levels of calcium are absorbed efficiently. In contrast, choice A (sodium) does not directly impact calcium absorption, choice B (intrinsic factor) is involved in the absorption of vitamin B12, not calcium, and choice D (Vitamin K) is essential for blood clotting but not directly related to calcium absorption. Therefore, Vitamin D is the correct choice as it directly influences the active absorption of calcium in the small intestine.

Correct Answer: C

Rationale: The correct answer is C: H+. Peptide transporter 1 requires a proton gradient for the active transport of di- and tripeptides across the enterocytes. This proton gradient is maintained by the H+ ions. Na+ (Choice A), Ca++ (Choice B), and Cl- (Choice D) are not directly involved in the transport of di- and tripeptides by peptide transporter 1. Na+ is primarily involved in glucose and amino acid transport, Ca++ in bone formation and muscle contraction, and Cl- in maintaining osmotic balance. Therefore, the correct answer is H+ as it is crucial for the functioning of peptide transporter 1.

Correct Answer: B

Rationale: The correct answer is B: cancer. T suppressor cells play a crucial role in regulating the immune response to prevent excessive activation, which can lead to the development of cancer. In cancer, T suppressor cells may become dysfunctional, allowing cancer cells to evade immune surveillance and proliferate. Autoimmune diseases (choice A) are more associated with a breakdown in immune tolerance, leading to an overactive immune response against self-antigens. Allergies (choice C) involve an exaggerated immune response to harmless substances, primarily driven by IgE antibodies and other immune cells, rather than T suppressor cells. Graft rejection (choice D) is typically mediated by T helper cells and cytotoxic T cells targeting foreign antigens present in transplanted tissues, rather than T suppressor cells.

Correct Answer: C

Rationale: The correct answer is C because glucose, fructose, and galactose are all monosaccharides, which are the simplest form of carbohydrates and can be directly absorbed by the intestinal cells through specific transport proteins. This process occurs through facilitated diffusion or active transport mechanisms. In contrast, choices A and B consist of disaccharides or polysaccharides, which need to be broken down into monosaccharides before absorption can occur. Choice D includes enzymes and disaccharides, which are not directly absorbed but rather involved in the digestion process. Thus, only choice C aligns with the mechanism of carbohydrate absorption in the intestines.

Correct Answer: C

Rationale: Rationale: A complete block at the AV node would prevent the transmission of the pacemaker signal from the SA node to the ventricles. As a result, the ventricles would not receive the signal to contract at their normal rate. Instead, they would rely on their inherent ability to generate impulses, resulting in a slower, but still rhythmic contraction. This scenario is known as an escape rhythm, where a lower pacemaker takes over in the absence of the SA node signal. Summary: A: the ventricles would cease beating - Incorrect, as the ventricles have their own intrinsic pacemaker. B: the ventricles would beat very fast and uncontrollably - Incorrect, as a complete AV block would lead to a slower rhythm. D: the ventricles would contract at the same rate as the atria - Incorrect, as the ventricles and atria have different intrinsic rates.