Nokea
Select the correct statement about the structure or function of chemical messengers.
- A. Prostaglandins are biologically active peptides.
- B. Modified cholesterol forms the main structural component of the peptone hormones.
- C. An amino acid derivative can be a hormone.
- D. An example of a paracrine is testosterone.
Correct Answer: C
Rationale: The correct answer is C: An amino acid derivative can be a hormone. This statement is correct because many hormones are derived from amino acids, such as thyroid hormones (derived from tyrosine) and epinephrine (derived from phenylalanine). Hormones can be derived from various sources, including amino acids, peptides, lipids, and even gases.
Explanation of other choices:
A: Prostaglandins are not biologically active peptides; they are lipid compounds derived from fatty acids.
B: Modified cholesterol does not form the main structural component of peptone hormones; peptides are the main structural components of peptide hormones.
D: Testosterone is a steroid hormone and not an example of a paracrine, which is a type of chemical messenger that acts on nearby cells.
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When blood glucose levels are low, the ______ will increase the secretion of ______.
- A. adrenal cortex: aldosterone
- B. pancreas; glucagon
- C. pancreas: insulin
- D. posterior pituitary: ADH
Correct Answer: B
Rationale: The correct answer is B: pancreas; glucagon. When blood glucose levels are low, the pancreas secretes glucagon. Glucagon acts to increase blood glucose levels by stimulating the liver to release stored glucose. The adrenal cortex does not directly regulate blood glucose levels through aldosterone secretion. Insulin is secreted by the pancreas in response to high blood glucose levels to lower them, not increase them. The posterior pituitary secretes ADH to regulate water balance, not blood glucose levels.
Steroid hormones _____________________.
- A. bind to a receptor inside the target cell
- B. are made from cholesterol
- C. cause the cell to make new proteins
- D. all of these
Correct Answer: D
Rationale: The correct answer is D because steroid hormones bind to a receptor inside the target cell, are made from cholesterol, and cause the cell to make new proteins. This is known as the mechanism of steroid hormone action. Choice A is correct as steroid hormones need to bind to intracellular receptors to exert their effects. Choice B is also correct as steroid hormones are derived from cholesterol. Choice C is correct as one of the main actions of steroid hormones is to regulate gene expression and induce the synthesis of new proteins within the cell. Therefore, all of these statements are true regarding steroid hormones, making choice D the correct answer.
Since Adonis was unable lift the dumbbell, he decided to use the exercise bike for a cardiovascular workout. During maximum exertion on the exercise bike, Adonis began to breathe heavily and felt 'the burn' in his legs. The skeletal muscles of his legs were using primarily which form of respiration at maximum exertion?
- A. Aerobic respiration
- B. Electron transport chain
- C. Oxidative phosphorylation
- D. Glycolysis
Correct Answer: d
Rationale: The correct answer is D: Glycolysis. During maximum exertion, skeletal muscles rely on glycolysis to quickly generate ATP without oxygen. This process breaks down glucose into pyruvate, producing a small amount of ATP. Since Adonis was feeling 'the burn' in his legs, it indicates the accumulation of lactic acid from glycolysis. Choice A (Aerobic respiration) requires oxygen and is not efficient during high-intensity exercise. Choices B (Electron transport chain) and C (Oxidative phosphorylation) are part of aerobic respiration and occur in mitochondria, which are less active during intense exercise compared to glycolysis.
Aldosterone:
- A. is a mineralocorticoid secreted by the adrenal cortex.
- B. functions in the regulation of blood glucose levels.
- C. stimulates the kidney to excrete sodium and reabsorb potassium.
- D. All is applicable.
Correct Answer: A
Rationale: Step-by-step rationale for why choice A is correct:
1. Aldosterone is a mineralocorticoid hormone secreted by the adrenal cortex.
2. It plays a key role in regulating electrolyte balance, specifically sodium and potassium levels.
3. Aldosterone acts on the kidneys to increase sodium reabsorption and potassium excretion.
4. This hormone helps to maintain blood pressure and fluid balance in the body.
Summary of why other choices are incorrect:
- Choice B (functions in the regulation of blood glucose levels): Aldosterone does not play a significant role in blood glucose regulation.
- Choice C (stimulates the kidney to excrete sodium and reabsorb potassium): This statement is partially true, but aldosterone actually stimulates sodium reabsorption and potassium excretion.
- Choice D (All is applicable): While aldosterone has various functions, not all statements apply to its actions.
Adrenaline combination with local anesthetics has the following effects EXCEPT:
- A. Reduces the absorption of local anesthetic
- B. Increases the duration of its local anesthetic activity
- C. Decreases the toxicity of the local anesthetic
- D. Increases blood flow to the injection area
Correct Answer: D
Rationale: Correct Answer: D. Increases blood flow to the injection area.
Rationale:
1. Adrenaline is a vasoconstrictor that reduces blood flow in the injection area.
2. By constricting blood vessels, adrenaline limits the absorption of the local anesthetic, leading to prolonged local action.
3. Adrenaline also helps in reducing the systemic toxicity of the local anesthetic by limiting its absorption.
4. Therefore, the correct answer is D as adrenaline does not increase blood flow to the injection area.