Nokea
What is a light-year?
- A. the distance travelled by light in a vacuum in 1 year
- B. the distance travelled by light in a vacuum in 100 000 years
- C. the time taken for light to travel across the Milky Way
- D. the time taken for light to travel from the Sun to the Earth
Correct Answer: A
Rationale: The correct answer is A: the distance travelled by light in a vacuum in 1 year. Light-year is a unit of astronomical distance, not time. Light travels at a constant speed in a vacuum, approximately 299,792 kilometers per second. In one year, light can travel about 9.46 trillion kilometers, which is defined as one light-year. Choices B, C, and D are incorrect because they do not accurately define a light-year in terms of distance traveled by light in a vacuum over a specific time period.
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Somatostatin secreted by the pancreas is considered paracrine because it acts on __________.
- A. the cells that secrete it
- B. distant target organs
- C. cells other than those that secrete it
- D. the hypothalamus to inhibit or activate the secretion of other hormones
Correct Answer: C
Rationale: The correct answer is C because somatostatin acts on nearby cells other than those that secrete it, which is the definition of paracrine signaling. This type of signaling involves the release of signaling molecules that affect neighboring cells within the same tissue or organ. Choices A and B are incorrect because paracrine signaling does not target the cells that secrete the signaling molecule or distant target organs. Choice D is incorrect because the hypothalamus is not typically the target of somatostatin action in the pancreas.
How do protein kinases affect enzymes?
- A. They add a phosphate group (phosphorylation) to the enzyme.
- B. They increase the release of an enzyme.
- C. They break down the enzyme.
- D. They increase the secretion of an enzyme.
Correct Answer: A
Rationale: Correct Answer: A
Rationale:
1. Protein kinases add a phosphate group to enzymes through phosphorylation.
2. Phosphorylation alters enzyme activity and can activate or deactivate enzymes.
3. This process regulates enzyme function and signaling pathways.
Summary of other choices:
B. Incorrect - Protein kinases do not increase enzyme release; they modify enzyme activity.
C. Incorrect - Protein kinases do not break down enzymes; they regulate their activity.
D. Incorrect - Protein kinases do not increase enzyme secretion; they modify enzyme function through phosphorylation.
The following drugs can depress the sympathetic activity EXCEPT:
- A. Clonidine
- B. Reserpine
- C. Phenylephrine
- D. Labetalol
Correct Answer: C
Rationale: The correct answer is C: Phenylephrine. Phenylephrine is a sympathomimetic drug that stimulates the sympathetic nervous system, leading to vasoconstriction and increased heart rate. In contrast, choices A, B, and D all work to depress sympathetic activity by different mechanisms. Clonidine is an alpha-2 adrenergic agonist that decreases sympathetic outflow. Reserpine inhibits the storage of norepinephrine, leading to decreased sympathetic activity. Labetalol is a non-selective beta blocker that blocks beta-adrenergic receptors, reducing sympathetic effects. Therefore, Phenylephrine is the only drug among the options that does not depress sympathetic activity.
Glucocorticoids enable the body to deal appropriately with stress. They accomplish this by ________.
- A. increasing blood glucose, fatty acid, and amino acid levels and enhancing blood pressure
- B. decreasing the heart rate, thus decreasing blood pressure
- C. stimulating the pancreas to release insulin
- D. blocking the neurotransmitters that prepare the body for the stress response
Correct Answer: A
Rationale: The correct answer is A because glucocorticoids, like cortisol, increase blood glucose levels through gluconeogenesis, elevate fatty acid levels for energy production, and promote amino acid breakdown for energy. This helps the body respond to stress by providing necessary energy sources. Additionally, glucocorticoids can enhance blood pressure to ensure adequate blood flow during stress.
Option B is incorrect because glucocorticoids typically increase heart rate and blood pressure to support the stress response. Option C is incorrect as glucocorticoids do not stimulate the release of insulin; instead, they can have an anti-insulin effect. Option D is incorrect as glucocorticoids do not block neurotransmitters but rather modulate the stress response at various levels.
Which row describes aqueous sodium chloride in process 1 and the name of process 2?
- A. residue, evaporation
- B. residue, filtration
- C. filtrate, evaporation
- D. filtrate, filtration
Correct Answer: C
Rationale: The correct answer is C: filtrate, evaporation. In process 1, aqueous sodium chloride would form the filtrate after filtration, as the solid residue is left behind. In process 2, evaporation is used to separate the solvent (water) from the dissolved salt, leaving behind the pure salt. Choice A is incorrect because residue is the solid left behind, not the liquid portion (filtrate). Choice B is incorrect as filtration results in the filtrate, not the residue. Choice D is incorrect as the filtrate undergoes evaporation, not filtration.