HESI A2 Biology Practice Test 2024

Correct Answer: B

Rationale: The correct answer is B: Nucleotides. DNA is made up of nucleotides, which are composed of a sugar molecule, a phosphate group, and a nitrogenous base. This structure forms the double helix shape of DNA. Proteins (option A) are not the building blocks of DNA, but they are involved in various cellular functions. Lipids (option C) and carbohydrates (option D) are not the primary components of DNA. Overall, nucleotides are the fundamental units of DNA, making option B the correct answer.

Correct Answer: D

Rationale: The primary function of the endoplasmic reticulum (ER) in a cell is the transport of materials. The ER consists of a network of membranes that help in the synthesis, folding, and transport of proteins and lipids. It plays a crucial role in the intracellular transport of materials between different cell compartments. This process ensures that newly synthesized proteins and lipids are properly transported to their respective destinations within the cell. The ER also serves as a site for the modification and packaging of proteins before they are transported to other organelles or secreted outside the cell. Therefore, the correct answer is D. Incorrect choices: A: Energy production - This is not the primary function of the ER. Energy production mainly occurs in mitochondria. B: Protein synthesis - While the ER is involved in protein synthesis, its primary function is the transport of materials. C: Waste removal - Waste removal is primarily carried out by lysosomes and peroxisomes in a cell, not the ER

Correct Answer: B

Rationale: The correct answer is B: Active Transport. Active transport moves substances across the cell membrane against the concentration gradient, requiring energy (usually in the form of ATP). This process is crucial for maintaining cellular homeostasis and allowing the cell to accumulate essential molecules. Passive transport (A) does not require energy and moves substances along the concentration gradient. Facilitated diffusion (C) is a type of passive transport that involves the use of transport proteins to move specific molecules across the membrane. Osmosis (D) is the movement of water across a selectively permeable membrane, also considered a type of passive transport.

Correct Answer: C

Rationale: The correct answer is C: Lipids. Plasma membranes are primarily composed of phospholipids, which form a lipid bilayer structure. This lipid bilayer provides a barrier that separates the internal and external environments of the cell. Proteins are also present in the plasma membrane, but they are not the main component. Carbohydrates are found on the surface of the membrane for cell recognition and signaling, but they do not make up the majority of the membrane. Nucleotides are building blocks of nucleic acids like DNA and RNA, not the main constituents of plasma membranes. In summary, lipids are the key component of plasma membranes, forming the structural basis for its function, making choice C the correct answer.

Correct Answer: B

Rationale: During metaphase of mitosis, chromosomes align at the cell's equator, forming the metaphase plate. This alignment ensures that during anaphase, sister chromatids separate and move towards opposite poles. Prophase is characterized by chromosome condensation, telophase marks the end of nuclear division. Anaphase involves the actual separation of chromatids. Metaphase is the correct answer as it is the phase where chromosomes are precisely aligned for accurate distribution to daughter cells.