HESI A2 Biology Practice Test 2024

Correct Answer: B

Rationale: The correct answer is B: Ribosomes. Ribosomes are the organelles responsible for protein synthesis. They are either free-floating in the cytoplasm or attached to the endoplasmic reticulum. Ribosomes read the mRNA and assemble amino acids into proteins during the process of translation. The other choices (A: Endoplasmic Reticulum, C: Lysosomes, D: Vacuoles) are incorrect because the endoplasmic reticulum is involved in protein processing and transport, lysosomes are involved in digestion and waste removal, and vacuoles are involved in storage and maintaining cell structure, not protein synthesis.

Correct Answer: B

Rationale: The main function of ribosomes is protein synthesis. Ribosomes are responsible for translating the genetic information encoded in mRNA into proteins. This process involves decoding the mRNA sequence and linking amino acids together to form a protein. Ribosomes do not participate in DNA replication (Choice A), lipid breakdown (Choice C), or cell division (Choice D). DNA replication occurs in the nucleus, lipid breakdown is carried out by enzymes in the cytoplasm, and cell division involves processes such as mitosis and cytokinesis. Therefore, the correct answer is B because ribosomes are directly involved in protein synthesis.

Correct Answer: C

Rationale: The correct answer is C: Cytoskeleton. The cytoskeleton provides structural support to the cell, helps maintain its shape, and allows it to adapt to external stimuli. It is composed of microfilaments, intermediate filaments, and microtubules. Microfilaments (choice A) play a role in cell movement but are not primarily responsible for maintaining cell shape. Cytoplasm (choice B) is the gel-like substance within the cell where organelles are suspended, but it does not directly contribute to maintaining cell shape. Centrioles (choice D) are involved in cell division and organization of microtubules, but they do not primarily help the cell maintain its shape and adapt.

Correct Answer: C

Rationale: The correct answer is C: Peroxisomes. Peroxisomes are responsible for detoxifying harmful substances in the cell by using enzymes to break down toxic molecules like hydrogen peroxide. This organelle contains catalase, an enzyme that converts hydrogen peroxide into water and oxygen. Endoplasmic Reticulum (choice A) is involved in protein synthesis and lipid metabolism. Lysosomes (choice B) are responsible for breaking down cellular waste and recycling materials. Golgi Apparatus (choice D) is involved in processing and packaging proteins for secretion. Therefore, Peroxisomes specifically handle detoxification, making it the correct choice.

Correct Answer: B

Rationale: Passive transport is the term for the movement of ions and other molecular substances across cell membranes without the need for energy. This process relies on the concentration gradient to drive molecules from an area of high concentration to an area of low concentration. Unlike active transport (choice A), which requires energy, passive transport does not involve energy consumption. Diffusion (choice C) is a type of passive transport where molecules move freely across the membrane. Osmosis (choice D) is a specific type of passive transport involving the movement of water molecules across a selectively permeable membrane.