Cells that respond to peptide hormones usually do so through a sequence of biochemical reactions involving receptor and kinase activation. In order for cells to respond, it is necessary for first and second messengers to communicate. This is possible because ________.

Correct Answer: C

Rationale: The correct answer is C: G protein acts as the link between first and second messengers. Rationale: 1. Peptide hormones cannot enter the cell membrane due to their large size. 2. Hormones do not directly stimulate genes; they act through signaling pathways. 3. G proteins are key in transmitting signals from hormone receptors to second messengers, facilitating cellular responses. 4. The hormone receptor complex typically stays on the cell membrane to initiate signaling cascades.

Correct Answer: B

Rationale: The correct answer is B: Calcium. Calcium ions are commonly used as second messengers for amino acid-base hormones due to their ability to trigger various cellular responses. When the hormone binds to its receptor on the cell surface, it activates specific signaling pathways that lead to an increase in intracellular calcium levels. This rise in calcium ions then initiates downstream signaling cascades, ultimately regulating processes such as gene expression, cell growth, and metabolism. Choice A - Iron: Iron is not typically involved in signaling pathways for amino acid-base hormones. It is more commonly known for its role in oxygen transport and storage in hemoglobin. Choice C - Sodium: While sodium ions play essential roles in cellular functions, they are not typically utilized as second messengers for amino acid-base hormones. Sodium is more commonly associated with maintaining cell membrane potential and fluid balance. Choice D - Chlorine: Chlorine ions are not typically involved in signaling pathways for amino acid-base hormones. Chlorine is primarily known for its role in maintaining

Correct Answer: C

Rationale: The correct answer is C: Pancreas. The pancreas is an endocrine gland located in the abdominal cavity near the small intestine. It secretes hormones like insulin and glucagon that regulate blood sugar levels. The adrenal gland (A) is located on top of the kidneys, the hypothalamus (B) is in the brain, and the thyroid gland (D) is located in the neck. These glands are not near the small intestine, making them incorrect choices.

Correct Answer: C

Rationale: The correct answer is C: growth hormone does not promote glucose metabolism. Growth hormone primarily promotes protein synthesis in bones, cartilage, and muscles (B), stimulates the rate of amino acid entrance into the cell (A), and promotes fat metabolism (D). Glucose metabolism is mainly regulated by insulin, not growth hormone.

Correct Answer: A

Rationale: The correct answer is A: sympathetic. Epinephrine and norepinephrine are neurotransmitters released by the sympathetic nervous system. They activate the fight-or-flight response, increasing heart rate, dilating airways, and redirecting blood flow to muscles. The sympathetic nervous system prepares the body for action in response to stress or danger. Choices B, C, and D are incorrect because parasympathetic regulates rest and digest functions, somatic controls voluntary movements, and central refers to the brain and spinal cord, not a division of the autonomic nervous system like sympathetic.