HESI A2 Biology Practice Test 2024

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: B

Rationale: The correct answer is B: Cell Membrane. The cell membrane serves as a selectively permeable barrier that controls the passage of substances into and out of the cell. It is composed of a phospholipid bilayer with embedded proteins that regulate the transport of molecules. The other choices are incorrect because: A: Vacuole - Vacuoles are membrane-bound organelles that mainly store water, ions, and nutrients. They do not control the passage of substances into and out of the cell. C: Nuclear Membrane - The nuclear membrane surrounds the nucleus and regulates the passage of molecules between the nucleus and the cytoplasm. It does not control the passage of substances into and out of the entire cell. D: Cytoplasm - Cytoplasm is the gel-like substance inside the cell that contains organelles. It does not directly control the passage of substances into and out of the cell; instead, it provides a medium for cellular activities to occur.

Correct Answer: B

Rationale: The correct answer is B: Cell. Cells are the fundamental unit of life because they are the basic building blocks of all living organisms. Cells carry out essential functions such as metabolism, growth, and reproduction. Tissues (C) are made up of cells, organs (D) are made up of tissues, and atoms (A) are the smallest unit of matter and are not considered the fundamental unit of life. Therefore, the correct choice is B as it represents the starting point of all living organisms.

Correct Answer: B

Rationale: The correct answer is B: Microtubules. Microtubules are cylindrical structures made up of tubulin proteins that provide structural support and serve as tracks for cellular movement. They are involved in various cellular processes, including cell motility and intracellular transport. Microfilaments (A) are involved in cell shape and movement but are not primarily responsible for cell propulsion. Flagella (C) and Cilia (D) are cellular appendages that aid in cell movement, but they are composed of microtubules and are not the primary structures responsible for providing the cell with the ability to move and propel.

Correct Answer: B

Rationale: The correct answer is B: Eukaryotic. Animal cells are eukaryotic cells because they have a defined nucleus that houses the genetic material. This nucleus is surrounded by a membrane, along with other membrane-bound organelles like mitochondria and endoplasmic reticulum. Prokaryotic cells (Option A) lack a true nucleus and membrane-bound organelles. Plant cells (Option C) have similar characteristics to animal cells but also have additional features like a cell wall and chloroplasts. Bacterial cells (Option D) are prokaryotic cells and differ significantly from animal cells in structure and function.