HESI A2 Practice Test Biology

Correct Answer: A

Rationale: The correct answer is A: Phospholipids. Phospholipids are essential components of the plasma membrane due to their amphipathic nature, with hydrophilic heads and hydrophobic tails. This structure allows phospholipids to form a lipid bilayer, creating a barrier that separates the internal and external environments of the cell. Steroids (B) are not a major component of the plasma membrane. Sugars (C) are found in glycoproteins and glycolipids on the membrane surface, but they are not the main structural component. Amino acids (D) are the building blocks of proteins, which can be membrane proteins, but they are not the key structural component of the membrane itself.

Correct Answer: A

Rationale: Transcription is the correct answer because it is the process where RNA is synthesized from a DNA template. It involves RNA polymerase binding to the DNA template and creating a complementary RNA strand by matching RNA nucleotides to the DNA template. Translation is incorrect as it involves the synthesis of proteins from mRNA. Transformation is a process in genetics unrelated to protein synthesis. Replication is the process of copying DNA to create two identical DNA molecules, not RNA synthesis from DNA.

Correct Answer: B

Rationale: The correct answer is B: Water keeps temperature stable. Water has a high specific heat capacity, meaning it can absorb and release large amounts of heat without changing temperature significantly. This property helps living things regulate their body temperature by absorbing excess heat in warm environments and releasing stored heat in cold environments. Options A, C, and D are incorrect because water does not directly increase or decrease temperature, but rather helps maintain stability by absorbing or releasing heat as needed.

Correct Answer: A

Rationale: The correct answer is A because DNA contains the genetic information needed for the synthesis of enzymes, which are crucial for metabolic activities in the cell. Enzymes are proteins that catalyze chemical reactions within the cell, allowing essential metabolic processes to occur. DNA serves as a template for the production of specific enzymes through the process of transcription and translation. Choices B, C, and D are incorrect because DNA does not directly play a role in stabilizing the cell wall, initiating cell division, or preventing diffusion of nutrients. These processes are regulated by other cellular components and mechanisms.

Correct Answer: D

Rationale: The correct answer is D: Nucleus. The nucleus contains the genetic material of the cell, which is stored in the form of DNA. It controls the cell's activities and serves as the command center. The Golgi apparatus (A) is involved in processing and packaging proteins, the ribosome (B) is responsible for protein synthesis, and the endoplasmic reticulum (C) is involved in protein synthesis and lipid metabolism. The nucleus is unique in its role as the organelle that houses the cell's genetic information.