HESI A2 Biology 2024

Correct Answer: B

Rationale: The correct answer is B: Glycerol. Phospholipids are composed of a phosphate group, two fatty acids, and a glycerol molecule. Triglycerides, on the other hand, consist of three fatty acid chains attached to a glycerol molecule. Therefore, phospholipids lack the monosaccharide component, not glycerol. Monosaccharides are simple sugars and are not typically found in phospholipids. Phosphates are actually a key component of phospholipids, as indicated by their name. Fatty acids are present in both phospholipids and triglycerides, so they are not the component lacking in phospholipids.

Correct Answer: A

Rationale: During anaphase, the correct answer is A because it is the phase where chromosomes move to opposite ends of the spindle. This separation ensures that each new cell receives a complete set of chromosomes. Choice B is incorrect because nuclear membrane and nucleoli disintegrate during prophase, not anaphase. Choice C is incorrect as chromatids line up at the center of the spindle during metaphase. Choice D is incorrect as the nuclear membrane and nucleoli do not form during anaphase but rather re-form during telophase.

Correct Answer: D

Rationale: The correct answer is D (46). Humans have 23 pairs of homologous chromosomes, totaling 46 chromosomes. Each pair consists of one chromosome from each parent. Choices A (13), B (23), and C (26) are incorrect as they do not represent the total number of pairs of homologous chromosomes in humans. A and C do not reflect the correct total number of chromosomes, while B only specifies the number of individual chromosomes, not pairs. Therefore, option D is the correct choice because it accurately represents the total number of homologous chromosome pairs in humans.

Correct Answer: C

Rationale: The correct answer is C: Osmosis. Osmosis is the process of water moving across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. In this scenario, the strong salt solution outside the bacteria creates a hypertonic environment, causing water to move out of the bacteria, leading to its shrinkage. Dehydration synthesis (A) is a process where molecules combine to form a larger molecule with the loss of water. Hydrolysis (B) is the opposite process where a larger molecule is broken down into smaller molecules by the addition of water. Isotonic transport (D) refers to the movement of molecules across a membrane to maintain equilibrium, not the specific process described in the question.

Correct Answer: B

Rationale: The correct answer is B: Carbohydrates and lipids. Carbohydrates are composed of carbon, hydrogen, and oxygen in a ratio of 1:2:1. Lipids are also made of carbon, hydrogen, and oxygen, but in different ratios. Proteins (choice A and C) contain nitrogen in addition to carbon, hydrogen, and oxygen. Nucleic acids (choice D) contain nitrogen, phosphorus, carbon, hydrogen, and oxygen. Therefore, only carbohydrates and lipids consist of only carbon, hydrogen, and oxygen.