HESI A2
HESI A2 Biology 2024
1. If bacteria are placed in a strong solution of salt water, they will shrink as water moves out of the bacteria. What is this process called?
- A. Dehydration synthesis
- B. Hydrolysis
- C. Osmosis
- D. Isotonic transport
Correct answer: C
Rationale: Osmosis is the process by which water molecules move across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. In this case, when bacteria are placed in a strong solution of salt water, the high concentration of solutes outside the bacteria causes water to move out of the bacteria, leading to shrinkage. This process is known as osmosis. Dehydration synthesis (Choice A) is a process where molecules combine by removing water. Hydrolysis (Choice B) is the breakdown of molecules by the addition of water. Isotonic transport (Choice D) does not accurately describe the specific movement of water in or out of bacterial cells in a hypertonic solution.
2. What helps the cell maintain its shape and allows it to adapt?
- A. Microfilaments
- B. Cytoplasm
- C. Cytoskeleton
- D. Centrioles
Correct answer: C
Rationale: The cytoskeleton is the correct answer. It provides structural support to the cell, helps maintain its shape, and enables it to adapt to different environments. Microfilaments are part of the cytoskeleton, but they alone do not encompass the entire cytoskeleton's functions. Cytoplasm is the fluid inside the cell where organelles are suspended and is not directly responsible for maintaining cell shape. Centrioles are involved in cell division and do not primarily contribute to maintaining the cell's shape and adaptation.
3. Where can epithelial tissue be found?
- A. Organ lining
- B. Heart muscle
- C. Tendons
- D. Spinal cord
Correct answer: A
Rationale: Epithelial tissue is primarily found lining the surfaces of organs, such as the skin and the linings of various internal organs like the digestive tract, respiratory tract, and blood vessels. It serves as a protective barrier and helps with absorption and secretion. Heart muscle is made up of cardiac muscle tissue, tendons are primarily composed of dense connective tissue, and the spinal cord is composed of nervous tissue, none of which are classified as epithelial tissue.
4. Which organelle is responsible for detoxifying harmful substances in the cell?
- A. Endoplasmic Reticulum
- B. Lysosomes
- C. Peroxisomes
- D. Golgi Apparatus
Correct answer: C
Rationale: The correct answer is C, Peroxisomes. Peroxisomes are responsible for detoxifying harmful substances in the cell by breaking down fatty acids and producing hydrogen peroxide. This process helps protect the cell from damage caused by toxic substances. Choice A, Endoplasmic Reticulum, is involved in protein and lipid synthesis, not detoxification. Choice B, Lysosomes, contain enzymes for digestion and waste removal, not primarily detoxification. Choice D, Golgi Apparatus, is responsible for modifying, sorting, and packaging proteins for secretion, not detoxification.
5. What happens to messenger RNA when it reaches the cytoplasm?
- A. It attaches to a ribosome.
- B. It unzips, exposing nitrogen bases.
- C. It pairs with the DNA bases.
- D. It pulls free of the DNA strand.
Correct answer: A
Rationale: Messenger RNA (mRNA) carries genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm. When mRNA reaches the cytoplasm, it attaches to a ribosome. The ribosome functions as the site for protein synthesis through translation, where the genetic code carried by mRNA is read and translated into a specific sequence of amino acids. Choices B, C, and D are incorrect because mRNA does not unzip, expose nitrogen bases, pair with DNA bases, or pull free of the DNA strand in the cytoplasm. The primary function of mRNA in the cytoplasm is to serve as a template for protein synthesis by binding to ribosomes.
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