HESI A2 Biology 2024

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.

Correct Answer: C

Rationale: The correct answer is C: Budding. Yeast reproduces asexually through budding, where a small "bud" grows on the parent cell and eventually detaches to become a new individual. This process allows for rapid reproduction and genetic variation. Binary fission (A) is a process of cell division commonly seen in bacteria, not yeast. Spore formation (B) involves the production of specialized reproductive cells called spores, which is not how yeast typically reproduces. Cloning (D) refers to the creation of genetically identical organisms, which is not the typical method of reproduction for yeast.

Correct Answer: B

Rationale: The correct answer is B: Vacuole. Vacuoles are organelles that provide storage space for the cell, storing water, nutrients, and waste products. They help maintain the cell's internal pressure and shape. Mitochondria (A) are responsible for energy production, not storage. The cell membrane (C) is a protective barrier, and ribosomes (D) are involved in protein synthesis, not storage. Therefore, only the vacuole fits the role of providing storage space for the cell.

Correct Answer: C

Rationale: Rationale: 1. The Krebs cycle produces ATP (A), CO2 (B), and NADH (D) as products. 2. Glucose (C) is not directly produced by the Krebs cycle; glucose is the starting molecule that enters glycolysis before the Krebs cycle. Summary: A, B, and D are products of the Krebs cycle, while glucose (C) is not directly produced by the Krebs cycle but is a substrate for glycolysis.

Correct Answer: D

Rationale: The correct answer is D: Decomposer. Decomposers have the greatest energy efficiency among the given choices because they obtain energy by breaking down organic matter into simpler substances. This process requires less energy compared to the consumption and digestion processes in herbivores, carnivores, and omnivores. Decomposers play a vital role in recycling nutrients in ecosystems. Herbivores, carnivores, and omnivores have lower energy efficiency as they need to expend energy in hunting, digesting, and metabolizing food sources.