HESI A2 Practice Test Biology

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: 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: B

Rationale: The correct answer is B: ATP. ATP (adenosine triphosphate) is the primary molecule responsible for storing and transferring energy in cells through its high-energy phosphate bonds. Glucose (choice A) is a source of energy but not a storage molecule. Fatty acids (choice C) are primarily used for long-term energy storage. Starch (choice D) is a polysaccharide used for energy storage in plants, but ATP is the main energy currency in all cells for immediate use.

Correct Answer: A

Rationale: During the S phase of the cell cycle, chromosomes are duplicated. This process involves the replication of DNA to ensure that each daughter cell receives an identical copy of the genetic material. This is crucial for cell division and passing on genetic information accurately. Cell growth occurs in the G1 phase, DNA synthesis occurs in the S phase, and DNA destruction does not occur during any phase of the cell cycle. Therefore, the correct answer is A because it specifically describes the key event that occurs during the S phase.

Correct Answer: D

Rationale: The correct answer is D because DNA controls the synthesis of enzymes, which are essential for carrying out metabolic activities in the cell. Enzymes are biological catalysts that regulate chemical reactions in the cell. DNA contains the genetic information needed to produce specific enzymes through the process of transcription and translation. Enzymes play a crucial role in breaking down nutrients, synthesizing molecules, and regulating metabolic pathways. A: DNA does not initiate cellular mitosis; that is controlled by other molecules. B: DNA is not responsible for providing cell wall stability; that is primarily the role of the cell wall structure itself. C: DNA is not directly involved in increasing glucose absorption; that is regulated by other mechanisms such as insulin signaling.