HESI A2 Practice Test Biology

Correct Answer: B

Rationale: The correct answer is B: hemoglobin. Hemoglobin is a protein because it is composed of amino acids linked together in a specific sequence to form a complex structure that carries oxygen in red blood cells. Cellulose (choice A) is a carbohydrate, estrogen (choice C) is a hormone, and ATP (choice D) is a nucleotide that serves as a source of energy in cells. Hemoglobin's role in oxygen transport and its structural composition as a sequence of amino acids classify it as a protein.

Correct Answer: C

Rationale: The correct answer is C, fermentation and cellular respiration, because both are catabolic pathways that lead to cellular energy production. Fermentation occurs in the absence of oxygen, producing a small amount of ATP. Cellular respiration, on the other hand, occurs in the presence of oxygen and is a more efficient process, producing a significantly higher amount of ATP. Choices A, B, and D are incorrect because internal respiration, external respiration, and anaerobic respiration do not directly lead to cellular energy production through catabolic pathways.

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: oxygen. Oxygen is not a product of the Krebs cycle; it is used as the final electron acceptor in the electron transport chain. Carbon dioxide (A) is a product of the Krebs cycle, produced during decarboxylation reactions. Adenosine triphosphate (ATP) (C) and energy carriers (D) such as NADH and FADH2 are also products of the Krebs cycle, as they are generated through the oxidation of substrates. Oxygen's role is crucial for the efficient functioning of aerobic respiration, but it is not a direct product of the Krebs cycle.

Correct Answer: C

Rationale: The correct answer is C: Selectively permeable. The phospholipid bilayer of the cell membrane allows the passage of certain molecules while restricting others based on their size, charge, and solubility. This selective permeability enables the cell to regulate the movement of substances in and out, maintaining homeostasis. Option A is incorrect because the cell membrane is not impermeable; it allows some substances to pass through. Option B is incorrect as it suggests all molecules can freely pass through, which is not the case. Option D is incorrect as it contradicts itself by combining selective and impermeable, which is not a characteristic of the cell membrane.