HESI A2
HESI A2 Biology 2024
1. How many pairs of homologous chromosomes do humans have?
- A. 13
- B. 23
- C. 26
- D. 46
Correct answer: D
Rationale: The correct answer is D: 46. Humans have 23 pairs of chromosomes, which include 22 pairs of autosomes and 1 pair of sex chromosomes. Homologous chromosomes are pairs of chromosomes that contain the same genes, one from each parent. Therefore, humans have a total of 46 chromosomes, with 23 pairs of homologous chromosomes. Choices A, B, and C are incorrect as they do not represent the total number of chromosomes in humans or the number of pairs of homologous chromosomes.
2. Cells that line the inner or outer surfaces of organs or body cavities are often linked together by intimate physical connections. These connections are referred to as ______.
- A. Separate desmosomes
- B. Ronofilaments
- C. Tight junctions
- D. Fascia adherens
Correct answer: C
Rationale: The correct answer is C: Tight junctions. Tight junctions, also known as zonula occludens, are the intimate physical connections between cells that line the inner or outer surfaces of organs or body cavities. These junctions form a virtually impermeable barrier to fluid, creating a tight seal between the cells. This helps in maintaining the integrity and function of the tissue as well as regulating the movement of substances across the cell layer. Choice A, Separate desmosomes, are cell structures that provide strong adhesion between cells but do not create a barrier to fluid. Choice B, Ronofilaments, is not a term used to describe the connections between cells. Choice D, Fascia adherens, are another type of cell junction involved in cell adhesion, but they are different from tight junctions in terms of their structure and function.
3. Athletes are often concerned with the question of what they need in their diets to increase muscle mass and strength. What biologic molecule would you recommend that would accomplish this?
- A. carbohydrates
- B. proteins
- C. lipids
- D. nucleic acids
Correct answer: B
Rationale: Proteins are essential for building and repairing muscle tissue. They contain amino acids, which are the building blocks of muscles. Athletes looking to increase muscle mass and strength should focus on consuming adequate amounts of high-quality proteins in their diets. Carbohydrates provide energy for workouts, lipids are important for overall health but do not directly contribute to muscle building, and nucleic acids are involved in genetic activities rather than muscle growth.
4. Which organism reproduces via spore formation?
- A. Shelf fungus
- B. Lemon tree
- C. Smallmouth bass
- D. Staphylococcus
Correct answer: A
Rationale: The correct answer is A, Shelf fungus. Shelf fungus reproduces via spore formation. Spores are tiny, reproductive cells that are released into the environment to be carried by air or water, allowing the fungus to spread and reproduce. The other choices are incorrect because Lemon tree reproduces via seeds, Smallmouth bass reproduce sexually through the fertilization of eggs by sperm, and Staphylococcus bacteria reproduce by binary fission, dividing into two identical daughter cells.
5. How is the plasma membrane arranged?
- A. In a single layer made of proteins
- B. In a double layer made of proteins
- C. In a single layer of phospholipids
- D. In a double layer of phospholipids
Correct answer: D
Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a phospholipid bilayer. This structure consists of two layers of phospholipid molecules with hydrophilic heads facing the exterior and hydrophobic tails facing the interior, providing a semipermeable barrier for the cell. Choice A is incorrect because the plasma membrane is not made of a single layer of proteins. Choice B is incorrect as the double layer is composed of phospholipids, not proteins. Choice C is incorrect as the plasma membrane is not made of a single layer of phospholipids but rather a double layer.
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