HESI A2
HESI A2 Biology Practice Test 2024
1. What molecule is primarily responsible for providing energy to the cell?
- A. ATP
- B. DNA
- C. ADP
- D. Glycogen
Correct answer: A
Rationale: Correct! ATP (Adenosine Triphosphate) is the main molecule that stores and provides energy for cellular activities. ATP is known as the energy currency of the cell, where energy released from the breakdown of nutrients is stored in the high-energy phosphate bonds of ATP. Choices B, C, and D are incorrect because DNA carries genetic information, ADP is the precursor of ATP, and glycogen is a polysaccharide used for energy storage, not direct energy provision.
2. Which, if any, of the following statements are true?
- A. Water boils at approximately 100°C (212°F) at standard atmospheric pressure
- B. The boiling point is the temperature at which the vapor pressure is higher than the atmospheric pressure around the water
- C. Water boils at a lower temperature in areas of lower pressure
- D. A and C are true
Correct answer: D
Rationale: Both statements A and C are true. Water indeed boils at approximately 100°C (212°F) at standard atmospheric pressure. However, water boils at a lower temperature in areas of lower pressure due to the decreased atmospheric pressure, which affects the vapor pressure and boiling point of water. Statement B is incorrect because the boiling point is the temperature at which the vapor pressure equals the external pressure (atmospheric pressure in this case), not when it is higher.
3. Which organism reproduces via binary fission?
- A. Mushroom
- B. Blue whale
- C. Rainbow trout
- D. Salmonella
Correct answer: D
Rationale: The correct answer is D, Salmonella. Salmonella bacterium reproduces via binary fission, a form of asexual reproduction where the cell divides into two daughter cells with identical genetic material. This process is common among bacteria and single-celled organisms. Mushrooms reproduce through spores, blue whales and rainbow trout reproduce sexually, involving the fusion of male and female gametes. Therefore, choices A, B, and C are incorrect as they do not reproduce through binary fission.
4. How many chromosomes do sperm and egg produce in meiosis?
- A. 46
- B. 23
- C. 45
- D. 24
Correct answer: B
Rationale: Sperm and egg cells undergo meiosis to form gametes with half the number of chromosomes found in somatic cells. Each sperm and egg cell produces 23 chromosomes through meiosis. Choice A is incorrect because 46 chromosomes represent the diploid number found in somatic cells. Choice C is incorrect as it is an uncommon number for chromosome production in human gametes. Choice D is incorrect as the total number of chromosomes in sperm or egg cells is 23, not 24.
5. As cattle graze, cattle egrets consume the insects they stir up. This is an example of ___________.
- A. Mutualism
- B. Parasitism
- C. Commensalism
- D. Competition
Correct answer: C
Rationale: Commensalism is a relationship between two species in which one benefits without affecting the other species. In this scenario, the cattle egrets benefit from the insects stirred up by cattle while the cattle are not significantly impacted by the presence of the egrets. The egrets obtain food easily, and the cattle are neither harmed nor helped by the egrets' presence, making it an example of commensalism. Mutualism involves both species benefiting, parasitism involves one species benefiting at the expense of the other, and competition involves both species being negatively affected by their interactions, none of which apply to the relationship between cattle and cattle egrets in this context.
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