Biology HESI A2 2024

Correct Answer: A

Rationale: Beeswax is a lipid because it is a natural substance primarily composed of esters of fatty acids and long-chain alcohols. Lipids are hydrophobic molecules that include fats, oils, and waxes. Beeswax fits this description due to its insolubility in water and its role in providing a protective barrier for bees' hives. Carbohydrates are composed of sugars, proteins are made up of amino acids, and nucleic acids are the building blocks of DNA and RNA. Therefore, choices B, C, and D are incorrect as they do not align with the chemical composition and characteristics of beeswax.

Correct Answer: C

Rationale: The correct answer is C because yeast carries out fermentation, producing ethanol and carbon dioxide. During fermentation, yeast breaks down sugars in the dough into ethanol and carbon dioxide gas. The carbon dioxide gas gets trapped in the dough, causing it to rise. Choice A is incorrect because yeast does not engage in photosynthesis. Choice B is incorrect because yeast does not carry out photosynthesis at all. Choice D is incorrect because yeast primarily produces carbon dioxide through fermentation, not aerobic respiration.

Correct Answer: D

Rationale: The correct answer is D: Carbohydrates. Glucose is a type of simple sugar and a carbohydrate. Carbohydrates are composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio, which is the molecular formula of glucose (C6H12O6). Proteins (choice A) are composed of amino acids, lipids (choice B) are composed of fatty acids and glycerol, and nucleic acids (choice C) are composed of nucleotides. Therefore, only carbohydrates, specifically glucose, contain the specific molecular structure that characterizes glucose.

Correct Answer: C

Rationale: The purpose of phloem tissue in plant stems is to conduct food throughout the plant. Phloem is responsible for transporting sugars, amino acids, and other organic compounds produced through photosynthesis from the leaves to other parts of the plant for growth and energy. This process is known as translocation. Choice A is incorrect because water is transported by xylem tissue, not phloem. Choice B is incorrect as phloem does not conduct light energy. Choice D is incorrect as carbon dioxide is absorbed by the plant through stomata and transported through the plant via diffusion, not through phloem tissue.

Correct Answer: C

Rationale: The correct answer is C: Producers > secondary consumers. This is true because producers, like plants, have the highest energy content in an ecosystem as they convert sunlight into energy through photosynthesis. Secondary consumers, such as carnivores, obtain energy by consuming primary consumers or other secondary consumers, resulting in a lower energy content compared to producers. A: Decomposers < secondary consumers - Incorrect. Decomposers break down organic matter, releasing nutrients, and have a lower energy content compared to secondary consumers. B: Primary consumers < producers - Incorrect. Primary consumers, like herbivores, consume producers directly, so they have a lower energy content than producers. D: Secondary consumers < primary consumers - Incorrect. Secondary consumers typically have a lower energy content than primary consumers as they obtain energy by consuming them.