Nokea
Which of the following molecules are found in substantial quantities in both the cell membrane and DNA?
- A. Nitrogenous bases
- B. Steroids
- C. Phosphate groups
- D. Lipids
Correct Answer: C
Rationale: Phosphate groups are crucial components of the DNA backbone, forming the phosphodiester bonds between nucleotides. In DNA, the phosphate group connects the 3' carbon of one nucleotide to the 5' carbon of the next nucleotide. In the cell membrane, phospholipids are the main components, with phosphate groups present in the hydrophilic head of the molecule. This key structural feature allows phospholipids to form the lipid bilayer that comprises the cell membrane. While nitrogenous bases are essential components of DNA, they are not found in substantial quantities in the cell membrane. Steroids are not typically abundant in either the cell membrane or DNA. Lipids, although present in the cell membrane, do not have the same substantial presence in DNA as phosphate groups do.
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Which of the following immune system molecules creates pores in the cell membrane of their target cells to destroy the cell?
- A. Lymphotoxins
- B. Perforins
- C. Interferons
- D. Cytokines
Correct Answer: B
Rationale: Perforins are immune system molecules that function by creating pores in the cell membrane of target cells. These pores compromise the cell's integrity, ultimately leading to cell destruction. Lymphotoxins induce cell death, but they do not create pores in the cell membrane like perforins. Interferons are signaling proteins that regulate the immune response, while cytokines are a diverse group of proteins involved in cell signaling during immune reactions. Perforins specifically target cell membranes, disrupting their integrity and leading to cell destruction, making them the correct answer in this context.
Which of the following cell types produce and release antibodies?
- A. Helper T cells
- B. Cytotoxic T cells
- C. Plasma B cells
- D. Natural Killer cells
Correct Answer: C
Rationale: Plasma B cells are specialized cells that are responsible for producing and releasing antibodies. These antibodies play a vital role in the immune response by recognizing and neutralizing harmful pathogens like bacteria and viruses. Helper T cells aid in activating B cells and other immune cells, cytotoxic T cells are involved in eliminating infected or abnormal cells, and natural killer cells are part of the innate immune system, targeting virus-infected and tumor cells.
Which of the following demonstrates a chemical reaction involving water?
- A. Water and oil separate when combined
- B. Water boils to produce steam at 100 degrees Celsius
- C. Water dissolves sugar
- D. Water produces gas when reacting with sodium metal
Correct Answer: D
Rationale: The correct answer is D because when water reacts with sodium metal, it produces hydrogen gas, indicating a chemical reaction. Options A, B, and C involve physical changes or processes like separation, phase change, and dissolution, respectively, which do not involve a chemical reaction. In option A, oil and water separating is a physical change due to differences in polarity. Option B describes a physical change where water undergoes a phase change from liquid to gas. Option C involves a physical change as sugar dissolves in water through a physical process without a chemical reaction occurring.
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.
In order to determine the effects of energy drinks on women's running speed, researchers gave 300 women an energy drink and then recorded the time it took each of them to run 2 miles. After collecting the results, researchers concluded that energy drinks increase the speed of running in women. Which of the following further tests would best help to support this conclusion? Repeat the same experiment, using 300 men.
- A. Repeat the experiment, giving half of the men water and the other half the energy drink.
- B. Repeat the experiment having half of the men run 2 miles and the other half run 5 miles.
- C. Repeat the experiment, giving the men two different energy drinks.
- D. Repeat the experiment, giving the men two different energy drinks.
Correct Answer: B
Rationale: To further support the conclusion that energy drinks increase running speed in women, the best approach would be to repeat the experiment with men. By having half of the men run 2 miles (similar to the original experiment with women) and the other half run a longer distance such as 5 miles, researchers can determine if the effects of energy drinks on running speed are consistent across different distances. This design allows for a comparative analysis between genders and varying running distances, providing a more comprehensive understanding of the impact of energy drinks on running performance.