HESI A2
HESI A2 Biology 2024
1. Ocean waves may tear sponges into pieces, each of which may grow into a new sponge. What is this form of reproduction called?
- A. Budding
- B. Vegetative propagation
- C. Binary fission
- D. Fragmentation
Correct answer: D
Rationale: Fragmentation is the form of asexual reproduction where an organism breaks into fragments, and each fragment can grow into a new individual. In the case of sponges being torn into pieces by ocean waves, each piece has the potential to develop into a new sponge, making fragmentation the correct answer in this scenario. Budding is a form of asexual reproduction where a new organism develops as an outgrowth from the parent organism. Vegetative propagation involves the growth of new individuals from plant parts like stems or roots. Binary fission is a method of reproduction seen in some single-celled organisms where one cell divides into two identical cells.
2. In a phospholipid molecule, the head:
- A. Is hydrophilic
- B. Is hydrophobic
- C. Is on the inner side of the layer
- D. Both A and C
Correct answer: D
Rationale: The head of a phospholipid is hydrophilic (water-loving) and is located on the outer side of the lipid bilayer, interacting with water molecules. This arrangement positions the hydrophobic tails inward, away from water. Therefore, the correct answer is D. Choice A is incorrect because the head is hydrophilic, not hydrophobic. Choice B is incorrect as the head is on the outer side, not the inner side of the layer.
3. Which of the following is true of optical microscopy?
- A. Utilizes scanning electrons
- B. Utilizes visible light
- C. Utilizes dye for samples
- D. More than one of the above is true
Correct answer: D
Rationale: The correct answer is D, 'More than one of the above is true.' Optical microscopy utilizes visible light (Choice B) and often involves the use of dyes for samples (Choice C). Using dyes helps enhance contrast, making it easier to visualize the structures being observed. Choice A is incorrect as optical microscopy does not utilize scanning electrons, but rather visible light.
4. 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.
5. The sum of all chemical reactions that occur in an organism is:
- A. product
- B. respiration
- C. metabolism
- D. synthesis
Correct answer: C
Rationale: Metabolism is the sum of all chemical reactions that occur within an organism to maintain life. It involves all the processes that break down molecules to release energy (catabolism) and build new molecules to support growth and maintenance (anabolism). Respiration refers specifically to the process of generating energy from the breakdown of glucose molecules. Synthesis is the creation of complex molecules from simpler ones. Therefore, metabolism is the most comprehensive term that encompasses all these processes within an organism.
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