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What is the main component of sweat?
- A. Urea
- B. Glucose
- C. Water
- D. Electrolytes
Correct Answer: C
Rationale: - Sweat is primarily composed of water, making up the majority of its content. Water helps regulate body temperature by evaporating from the skin's surface, which cools the body down.
- While sweat does contain small amounts of other substances like urea, glucose, and electrolytes, water is the main component that is secreted by sweat glands to help regulate body temperature during physical activity or in response to heat.
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Which of the following glands is NOT directly controlled by the pituitary gland?
- A. Thyroid gland
- B. Adrenal glands
- C. Pancreas (Islets of Langerhans)
- D. Parathyroid glands
Correct Answer: C
Rationale: The pituitary gland, known as the master gland, regulates various endocrine glands by releasing specific hormones. The thyroid gland, adrenal glands, and parathyroid glands are directly controlled by the pituitary gland through hormones like thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), and parathyroid hormone (PTH) respectively. However, the pancreas, particularly the Islets of Langerhans, is not directly influenced by the pituitary gland. The pancreas is mainly governed by blood glucose levels and hormones such as insulin and glucagon, which play a crucial role in regulating blood sugar levels and metabolism. Therefore, the correct answer is C. Choice A, the thyroid gland, is controlled by the pituitary gland through TSH. Choice B, the adrenal glands, are regulated by the pituitary gland via ACTH. Choice D, the parathyroid glands, are under the direct control of the pituitary gland through PTH.
The pH scale is used to indicate the concentration of:
- A. Hydrogen ions
- B. Oxygen
- C. Salts
- D. Sugar molecules
Correct Answer: A
Rationale: The pH scale is a measure of the concentration of hydrogen ions in a solution, representing its acidity or basicity. A lower pH value indicates higher hydrogen ion concentration and acidity, while a higher pH value indicates lower hydrogen ion concentration and basicity. Choice A, 'Hydrogen ions,' is the correct answer because the pH scale specifically measures the concentration of hydrogen ions in a solution. Choices B, C, and D are incorrect as the pH scale is not used to indicate the concentration of oxygen, salts, or sugar molecules.
Antigenic variation, a common strategy used by some viruses, allows them to:
- A. Produce toxins
- B. Evade the immune system
- C. Survive outside a host
- D. Replicate rapidly
Correct Answer: B
Rationale: Antigenic variation is a strategy used by some viruses to evade the host's immune response. By constantly changing their surface antigens, viruses can avoid recognition and destruction by the immune system. This allows the virus to persist in the host and continue replicating, leading to prolonged infection and potential transmission to other hosts. Antigenic variation does not directly involve the production of toxins, survival outside a host, or rapid replication, making options A, C, and D incorrect in this context.
What type of nuclear force is responsible for holding protons and neutrons together in the nucleus of an atom?
- A. Electromagnetism
- B. Gravity
- C. Strong nuclear force
- D. Weak nuclear force
Correct Answer: C
Rationale: The correct answer is the strong nuclear force. It is an incredibly powerful force that overcomes the repulsive electrostatic force between protons, binding them together and stabilizing the nucleus. The strong nuclear force is essential for maintaining the integrity and stability of an atom's nucleus. Electromagnetism (Choice A) is responsible for interactions between charged particles but is not the primary force holding the nucleus together. Gravity (Choice B) is a very weak force at the nuclear level and is not responsible for binding protons and neutrons in the nucleus. The weak nuclear force (Choice D) is involved in certain types of radioactive decay processes, but it is not the force responsible for holding the nucleus together.
How does kinetic energy change when the velocity of an object is doubled?
- A. Kinetic energy is halved
- B. Kinetic energy quadruples
- C. Kinetic energy doubles
- D. Kinetic energy remains the same
Correct Answer: B
Rationale: Kinetic energy is directly proportional to the square of the velocity of an object according to the kinetic energy formula (KE = 0.5 * m * v^2). When the velocity is doubled, the kinetic energy increases by a factor of 2^2 = 4. Therefore, the kinetic energy quadruples when the velocity of an object is doubled. Choice A is incorrect because halving the kinetic energy would be the result if the velocity was halved, not doubled. Choice C is incorrect because doubling the velocity would result in a fourfold increase in kinetic energy, not just a double. Choice D is incorrect because kinetic energy is directly related to the velocity of an object, so if the velocity changes, the kinetic energy changes accordingly.