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A student makes a solution that simulates stomach acid. Which of the following would be true of this solution, compared to distilled water?
- A. It has a higher pH.
- B. It has more hydrogen ions.
- C. It contains more hydroxyl ions.
- D. It has more hydroxyl ions.
Correct Answer: B
Rationale: The correct answer is B. A solution that simulates stomach acid is acidic, which means it has a higher concentration of hydrogen ions compared to distilled water, which is neutral. Stomach acid is characterized by its high hydrogen ion concentration, which is responsible for its acidic nature. Hydroxyl ions are associated with bases, not acids, so options C and D are incorrect. Option A is incorrect as well because stomach acid would have a lower pH compared to distilled water due to its high acidity.
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Which term describes the relaxation of the chambers of the heart during the cardiac cycle?
- A. Tachycardia
- B. Diastole
- C. Systole
- D. Bradycardia
Correct Answer: B
Rationale: During the cardiac cycle, diastole represents the relaxation phase of the heart chambers. In diastole, the heart muscles relax, allowing the chambers to fill with blood. Tachycardia and bradycardia are terms used to describe heart rate abnormalities, while systole refers to the contraction phase of the heart when blood is pumped out of the chambers. Understanding the different phases of the cardiac cycle is crucial in comprehending how the heart functions to pump blood effectively. Diastole plays a vital role in ensuring that the heart chambers are adequately filled with blood before the next contraction phase, systole, propels the blood out to the rest of the body. This coordination between diastole and systole is essential for maintaining proper cardiac function and circulation.
Lithium has an atomic number of 3 and a mass number of 7. What is the number of protons in a lithium atom?
- A. 7
- B. 4
- C. 12
- D. 3
Correct Answer: D
Rationale: The number of protons in an atom is equal to its atomic number. In this case, lithium has an atomic number of 3, so it contains 3 protons. The mass number (7) includes both protons and neutrons, with the difference between the mass number and atomic number representing the number of neutrons. Therefore, the correct answer is 3 protons in a lithium atom.
What summarizes a change that occurs as solids transition into liquids?
- A. Particles become less ordered
- B. Particles increase in mobility
- C. Particles move further apart
- D. Intermolecular forces between particles weaken
Correct Answer: A
Rationale: The correct answer is A. When solids transition into liquids, particles become less ordered. In a solid state, particles are arranged in a fixed, orderly pattern due to strong intermolecular forces. As the solid transitions into a liquid, these forces weaken, allowing the particles more freedom of movement. Consequently, the particles become less ordered in a liquid compared to a solid, where they have more mobility and are not bound in a fixed structure.
Which of the following chemicals is released by one type of immune cell to directly activate another immune cell?
- A. lysozymes
- B. cytokines
- C. perforin
- D. granzymes
Correct Answer: B
Rationale: The correct answer is B: cytokines. Cytokines are signaling molecules released by immune cells to regulate the immune response. They play a crucial role in coordinating and communicating between different immune cells. By releasing cytokines, immune cells can directly activate other immune cells, enhancing the immune response. Lysozymes are enzymes that break down bacterial cell walls, perforin is a protein involved in cell-mediated immune responses, and granzymes are enzymes that induce apoptosis in target cells, mainly used by cytotoxic T cells and natural killer cells, not for directly activating other immune cells.
Which of the following allows the skull to rotate on the neck?
- A. Vertebral foramen
- B. Spinous process
- C. Atlas
- D. Sacrum
Correct Answer: C
Rationale: The atlas is the first cervical vertebra that supports the skull and allows it to rotate on the neck. The vertebral foramen is an opening in the vertebra for the spinal cord, and the spinous process is a bony projection, not involved in rotation.