Insulin:

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: 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.

Correct Answer: C

Rationale: The correct term for the digestive tract that begins at the mouth and finishes at the anus is called the alimentary canal. This term specifically refers to the entire passage through which food passes and is digested. The term "alimentary" pertains to nourishment or nutrition, making it the most accurate description of the digestive tract. A: Digestive passage is too broad and vague, not specifying the entire route of digestion. B: Elementary canal is not a commonly used term in anatomy to describe the digestive tract. D: Intestinal tract specifically refers to the section of the digestive system that includes the small and large intestines, excluding the mouth, esophagus, and stomach.

Correct Answer: D

Rationale: The correct order is D: Duodenum, jejunum, ileum. The duodenum is the first part of the small intestine connected to the stomach for digestion. Next is the jejunum, where most of the nutrients are absorbed. Lastly, the ileum completes the absorption process before reaching the large intestine. Choice A is incorrect as it has the parts in the wrong order. Choice B also has the parts in the wrong order. Choice C has the duodenum and ileum in the correct position but switches the jejunum and ileum.

Correct Answer: A

Rationale: The correct answer is A because it states that none of the above choices are similarities between hormones and neurotransmitters. This is accurate as choices B, C, and D all highlight similarities between hormones and neurotransmitters. Choice B is correct as both are chemical messengers, choice C is correct because some hormones and neurotransmitters can be chemically identical, and choice D is correct because both produce molecules that act on receptors. Therefore, A is the correct choice as it states that there are no similarities between the two, which is not the case.