HESI A2 Biology Practice Test 2024

Correct Answer: B

Rationale: Osmosis is the correct answer as it specifically refers to the movement of water molecules through a selectively permeable membrane. During osmosis, water moves from an area of higher concentration to an area of lower concentration to equalize the concentration on both sides of the membrane. This process does not require energy input and is crucial for maintaining the balance of water in cells. Diffusion (A) involves the movement of molecules from an area of high concentration to low concentration, but it is not specific to water molecules through a membrane. Active Transport (C) requires energy to move molecules against their concentration gradient, which is not the case in osmosis. Facilitated Diffusion (D) also involves the movement of molecules across a membrane, but it requires the assistance of specific carrier proteins, unlike the passive movement of water in osmosis.

Correct Answer: B

Rationale: The magnification of an ocular lens on a microscope is typically 10x. This is because the ocular lens standard magnification is 10x, which, when combined with the objective lens magnification (e.g., 4x, 40x, 100x), gives the total magnification. Therefore, the correct answer is B (10x). Choice A (4x) is incorrect as it is typically the magnification of a lower-powered objective lens, not the ocular lens. Choice C (40x) and Choice D (100x) are incorrect as they are higher magnifications typically associated with objective lenses, not the ocular lens.

Correct Answer: B

Rationale: The correct answer is B: Vacuoles (contractile). Contractile vacuoles are responsible for pushing excess water out of the cell through a process called osmoregulation. They maintain the cell's internal water balance by collecting and expelling water to prevent the cell from bursting due to osmotic pressure. Lysosomes (A) are involved in cellular waste disposal, mitochondria (C) are the powerhouse of the cell, and the nucleus (D) contains genetic material but does not play a role in expelling water from the cell.

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: The main component of blood plasma is water. Plasma is the liquid component of blood, making up about 55% of total blood volume. It serves as a carrier for various substances such as nutrients, waste products, hormones, and electrolytes. Water helps maintain blood volume, regulates body temperature, and facilitates the transport of essential components throughout the body. Proteins, red blood cells, and platelets are also present in blood plasma but are not the main component. Proteins play a role in clotting and immune function, red blood cells carry oxygen, and platelets aid in blood clotting. Water is the correct answer as it is the primary constituent of blood plasma.