Nokea
What is the primary function of hair on the human body?
- A. Insulation
- B. Sensory perception
- C. Protection
- D. Vitamin D synthesis
Correct Answer: C
Rationale: The primary function of hair on the human body is protection. Hair acts as a barrier to protect the skin from external factors such as sunlight, dust, and other environmental elements. While hair can also provide some insulation by trapping heat near the body and contribute to sensory perception by detecting touch or movements, its main role is to safeguard the skin from potential harm, making protection the most essential function. Vitamin D synthesis is primarily related to the skin's exposure to sunlight and is not a direct function of hair.
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Which of the following best describes a chemical change?
- A. Melting ice to form water
- B. Dissolving sugar in water
- C. Burning wood to produce ash
- D. Crushing a can to reduce its size
Correct Answer: C
Rationale: A chemical change involves a chemical reaction where new substances are formed. Burning wood to produce ash is an example of a chemical change because the wood undergoes a chemical reaction to form a new substance (ash). In this process, the chemical composition of wood changes to produce ash, which is a new substance. On the other hand, melting ice to form water, dissolving sugar in water, and crushing a can to reduce its size are examples of physical changes. In these instances, the substances may change their physical state or appearance but do not undergo a chemical reaction to form new substances. Therefore, choice C is the correct answer as it represents a chemical change, while choices A, B, and D represent physical changes.
Ectopic pregnancy is a serious condition that occurs when a fertilized egg implants outside the uterus. What is the most common location for an ectopic pregnancy?
- A. Ovary
- B. Fallopian tube
- C. Cervix
- D. Vagina
Correct Answer: B
Rationale: The most common location for an ectopic pregnancy is the fallopian tube. This occurs when the fertilized egg implants and grows outside the uterus, typically in the fallopian tube. Ectopic pregnancies in other locations such as the ovary, cervix, or vagina are much rarer. The fallopian tube is the correct answer because it is the site where the fertilized egg may get stuck during its journey to the uterus, leading to implantation and growth outside the uterus. The ovary is not a common site for ectopic pregnancy, and implantation there can be life-threatening due to the risk of severe bleeding. The cervix and vagina are not typical sites for implantation of a fertilized egg, making them less likely locations for an ectopic pregnancy.
What is the significance of the nuclear envelope breaking down during mitosis?
- A. It allows the chromosomes to condense and become visible.
- B. It allows the spindle apparatus to form and attach to the chromosomes.
- C. It allows the sister chromatids to separate.
- D. It allows the nuclear material to be evenly distributed to the daughter cells.
Correct Answer: B
Rationale: A) The breakdown of the nuclear envelope does not directly cause the chromosomes to condense and become visible. Chromosome condensation is a separate process that occurs before mitosis begins.
B) The breakdown of the nuclear envelope is crucial for the formation of the spindle apparatus, a structure made of microtubules that helps separate the chromosomes during cell division. The spindle apparatus attaches to the chromosomes and helps move them to opposite poles of the cell.
C) The separation of sister chromatids occurs during anaphase, which is facilitated by the spindle apparatus. The breakdown of the nuclear envelope is not directly involved in this process.
D) The even distribution of nuclear material to daughter cells is achieved through the movement of chromosomes by the spindle apparatus, which is made possible by the breakdown of the nuclear envelope.
Which of the following units is used to express concentration as a mass of solute per unit volume of solution?
- A. Molality (m)
- B. Molarity (M)
- C. Weight percent (%)
- D. Parts per million (ppm)
Correct Answer: A
Rationale: Molality (m) is the unit used to express concentration as a mass of solute per unit volume of solution. It is calculated by dividing the mass of solute in grams by the mass of the solvent in kilograms. Molality is preferred over molarity when there are large temperature variations as it is temperature-independent, making it a more accurate measure of concentration. Molarity (B) is the unit used to express concentration as moles of solute per liter of solution, weight percent (C) is the mass of solute per 100 parts of the total mass of the solution, and parts per million (D) is used to express very small concentrations where 1 ppm is equivalent to 1 mg of solute per liter of solution.
Positron emission tomography (PET) scans utilize a key property of positrons for medical imaging. What is this property?
- A. High mass
- B. Positive charge
- C. Extreme stability
- D. Identical behavior to electrons
Correct Answer: B
Rationale: Positron emission tomography (PET) scans utilize the property of positrons having a positive charge. Positrons are the antimatter counterpart of electrons, having the same mass but opposite charge. When a positron collides with an electron, they annihilate each other, producing gamma rays that can be detected by the PET scanner to create images of the body's internal structures and functions. Choice A is incorrect because positrons have the same mass as electrons. Choice C is incorrect as positrons are not extremely stable due to their tendency to annihilate when they encounter electrons. Choice D is incorrect as positrons exhibit different behavior than electrons due to their opposite charges.