HESI A2 Biology 2024

Correct Answer: A

Rationale: The correct answer is A: Hydrogen atoms. Saturated fats have all of their carbon atoms bonded to hydrogen atoms, with no double bonds between carbon atoms. This results in a "saturated" molecule with as many hydrogen atoms as possible. Choices B, C, and D are incorrect because saturated fats are not saturated with carbon, oxygen, or nitrogen atoms. These choices do not accurately reflect the chemical structure of saturated fats, which are primarily composed of carbon and hydrogen atoms.

Correct Answer: A

Rationale: The correct answer is A because it involves testing the impact of radiation from a single cell phone on the temperature of water in a test tube in a controlled manner. By letting the phone ring for two minutes and recording the temperature before and after, the researcher can isolate the effects of radiation. Choice B introduces additional variables by varying the ringing time, making it difficult to determine the specific impact of radiation. Choice C introduces the factor of different cell phone brands, which may have varying radiation levels and could confound the results. Choice D also introduces multiple variables by using different ringing times and phone brands, making it challenging to attribute any temperature changes solely to radiation from the cell phones. Therefore, choice A is the most appropriate as it ensures a controlled experiment to directly test the hypothesis regarding the impact of cell phone radiation on water temperature.

Correct Answer: D

Rationale: The correct answer is D: Citric acid. Citric acid is not a component of DNA nucleotides. A DNA nucleotide consists of a simple sugar (deoxyribose), a nitrogen base (adenine, thymine, cytosine, or guanine), and a phosphate group. Citric acid is not part of the structure of DNA; it is a component of the citric acid cycle in cellular respiration. Therefore, it is not found in the nucleotide of DNA. The other choices (A, B, and C) are all components that make up a DNA nucleotide, making them incorrect options.

Correct Answer: B

Rationale: The correct answer is B: Green. Chlorophyll, the pigment responsible for photosynthesis, absorbs light most efficiently in the red and blue regions of the spectrum. Green light is reflected, making it least effective. Violet, orange, and red lights are more readily absorbed by chlorophyll, enhancing photosynthesis. This is due to the specific absorption spectrum of chlorophyll, where green light is least absorbed.

Correct Answer: A

Rationale: The correct answer is A: Golgi apparatus. Protists are eukaryotic organisms, so they have membrane-bound organelles like the Golgi apparatus. Monerans, which are prokaryotic organisms, lack membrane-bound organelles. The Golgi apparatus is essential for processing and packaging proteins for secretion or for use within the cell. Chromosomes (B) are found in both protists and monerans, as they contain genetic material. Cytoplasm (C) is a basic component of all cells, found in both protists and monerans. Cell membrane (D) is also present in both protists and monerans, as it is essential for maintaining cell structure and regulating the movement of substances in and out of the cell.