Carbohydrate absorption:

Correct Answer: B

Rationale: Rationale: - GLUT2 transporter on basolateral membrane transports glucose, galactose, and fructose. - SGLT-2 transporter on apical membrane co-transports glucose and galactose with Na. - Fructose absorption is via facilitated diffusion, not secondary active transport. - Insulin increases, not decreases, carbohydrate absorption.

Correct Answer: D

Rationale: The correct answer is D: submandibular glands. These glands produce the majority of salivary volume due to their larger size and higher rate of saliva production compared to other salivary glands. Submandibular glands secrete a combination of serous and mucous saliva, contributing to overall saliva volume. The lingual glands (choice A) are smaller and contribute a smaller amount of saliva. The sublingual glands (choice B) are also smaller and produce less saliva compared to the submandibular glands. The parotid glands (choice C) are the largest salivary glands but contribute a smaller volume of saliva compared to the submandibular glands.

Correct Answer: B

Rationale: The correct answer is B because insulin deficiency leads to increased gluconeogenesis due to the lack of inhibition on glucose production. Choice A is incorrect as insulin binds to GLUT 4 receptors, not GLUT 1-5. Choice C is wrong because insulin's half-life is only a few minutes. Choice D is also inaccurate as insulin is secreted by pancreatic beta cells, not A cells.

Correct Answer: B

Rationale: Step-by-step rationale for the correct answer (B): 1. During starvation, the body shifts to using ketoacids derived from fats for fuel. 2. The brain and other tissues can utilize these ketoacids. 3. This process helps to spare protein and prevent muscle breakdown. 4. Therefore, choice B is correct as ketoacids play a crucial role in providing energy during starvation. Summary of why other choices are incorrect: A: Glycogen stores are depleted within 24 hours, not 48 hours. C: Hypoglycemia during starvation does not have a protein sparing effect. D: The average time until death from starvation is typically much shorter than 40 days.

Correct Answer: C

Rationale: The correct answer is C: negative feedback mechanism. This is because the majority of hormones in the endocrine system are regulated by a feedback loop that maintains homeostasis by inhibiting further hormone production when levels are too high and stimulating production when levels are too low. This negative feedback mechanism ensures that hormone levels remain within a narrow range. A: hormone-gene complex is incorrect as hormones are not primarily regulated by direct interactions with genes. B: hormone-receptor complex is incorrect as receptors are involved in hormone action, not regulation. D: positive feedback mechanism is incorrect as it would lead to an amplification of hormone production, which is not typically seen in the endocrine system to maintain stability.