HESI A2 Practice Test Biology

Correct Answer: B

Rationale: The correct answer is B: Ribosome. Ribosomes are responsible for organizing protein synthesis by translating mRNA into protein. They are the cellular machinery where protein synthesis occurs. The nucleus (A) houses the genetic material but does not directly participate in protein synthesis. Lysosomes (C) are responsible for cellular waste digestion, not protein synthesis. Vacuoles (D) are primarily storage organelles and do not play a direct role in organizing protein synthesis. In summary, the ribosome is the correct answer as it is the key organelle directly involved in protein synthesis within the cell.

Correct Answer: B

Rationale: The correct answer is B: Sexual reproduction and asexual reproduction. Sexual reproduction involves the fusion of gametes from two parents to create offspring with genetic variation. Asexual reproduction involves a single parent producing genetically identical offspring. Option A is incorrect because binary fission is a form of asexual reproduction, not sexual reproduction. Option C is incorrect because binary fission is a specific type of asexual reproduction, not the only category. Option D is incorrect because mitosis is a cell division process within asexual reproduction, but it is not a category of cell reproduction on its own.

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: 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: 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.