What are the white blood cells responsible for coordinating the immune response called?
- A. Red blood cells
- B. Platelets
- C. Lymphocytes
- D. Neutrophils
Correct Answer: C
Rationale: Lymphocytes, which include B cells, T cells, and natural killer cells, are responsible for coordinating the immune response. They play a crucial role in recognizing and fighting against pathogens and foreign substances in the body. Red blood cells are responsible for oxygen transport, platelets aid in blood clotting, and neutrophils are white blood cells primarily involved in combating infections. Therefore, the correct answer is C, lymphocytes, as they are specifically involved in coordinating immune responses.
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In a neutral atom, the number of electrons is:
- A. Must be equal to the number of protons.
- B. Must be less than the number of protons.
- C. Must be greater than the number of neutrons.
- D. Can vary depending on the atom's temperature.
Correct Answer: A
Rationale: In a neutral atom, the number of electrons must be equal to the number of protons to maintain electrical neutrality. Electrons carry a negative charge while protons carry a positive charge. By having an equal number of electrons and protons, the positive and negative charges balance each other out, resulting in an electrically neutral atom. Choice B is incorrect because in a neutral atom, the number of electrons and protons must be equal. Choice C is incorrect as it compares electrons to neutrons, which are not directly related in determining an atom's charge. Choice D is incorrect as the number of electrons in a neutral atom is not dependent on the atom's temperature but rather on the atom's balance of positive and negative charges.
In meiosis, how many divisions occur, and how many daughter cells are produced?
- A. One division, two daughter cells
- B. Two divisions, four daughter cells
- C. Four divisions, eight daughter cells
- D. Eight divisions, sixteen daughter cells
Correct Answer: B
Rationale: In meiosis, there are two divisions: meiosis I and meiosis II. During meiosis I, homologous chromosomes separate, resulting in two daughter cells with half the number of chromosomes as the parent cell. In meiosis II, sister chromatids separate, resulting in a total of four daughter cells, each with a haploid set of chromosomes. Therefore, meiosis involves two divisions and produces four daughter cells. Choice A is incorrect because meiosis involves two divisions, not one. Choice C and D are incorrect as meiosis does not go through four or eight divisions, resulting in eight or sixteen daughter cells.
What is the muscular sac in the female body that nourishes and protects a developing fetus during pregnancy?
- A. Ovary
- B. Fallopian tube
- C. Uterus
- D. Vagina
Correct Answer: C
Rationale: The correct answer is the uterus. The uterus is a muscular organ in the female body where a developing fetus is nourished and protected during pregnancy. It is the site where a fertilized egg implants and grows into a fetus. The ovaries produce eggs, the fallopian tubes transport the egg to the uterus for potential fertilization, and the vagina serves as the birth canal and the passage for menstrual blood to exit the body. Therefore, the uterus plays a crucial role in pregnancy by providing a nurturing environment for the developing fetus.
Osteoporosis is a condition that leads to weakened bones and an increased risk of fractures. Which hormone plays a key role in bone health and is often affected in osteoporosis?
- A. Estrogen
- B. Testosterone
- C. Thyroid hormone
- D. Insulin
Correct Answer: A
Rationale: Estrogen plays a crucial role in maintaining bone health by inhibiting bone resorption and promoting bone formation. In postmenopausal women, estrogen levels decrease, leading to an increased risk of osteoporosis due to accelerated bone loss. This hormonal imbalance contributes to weakened bones and an increased risk of fractures in individuals with osteoporosis. Testosterone and thyroid hormone do play roles in bone health, but estrogen has a more significant impact. Testosterone is more commonly associated with muscle mass and strength, while thyroid hormone regulates metabolism. Insulin is not directly involved in bone health and is not typically affected in osteoporosis.
Which of the following statements is true regarding a supersaturated solution?
- A. It is unstable and tends to crystallize
- B. It contains more solute than it could dissolve
- C. It has a higher concentration than a saturated solution
- D. It is rarely encountered in everyday solutions
Correct Answer: A
Rationale: A supersaturated solution is unstable and tends to crystallize because it contains more solute than it could dissolve at a given temperature. This excess solute is in a metastable state and can precipitate out if disturbed, leading to the formation of crystals. Option B is incorrect because a supersaturated solution does contain more solute than it could normally dissolve, but it becomes unstable due to this excess solute. Option C is incorrect because while a supersaturated solution does have a higher concentration than a saturated solution, the defining characteristic related to its instability is the excess solute. Option D is incorrect as supersaturated solutions can be encountered in various everyday scenarios, such as certain sugar solutions used in cooking or rock candy production.