HESI A2 Practice Test Biology

Correct Answer: B

Rationale: The correct answer is B because lipids are nonpolar molecules, making them hydrophobic and insoluble in water. This is due to their long hydrocarbon chains that repel water molecules. Choice A is incorrect because lipids are composed of fatty acids and glycerol, which are separate components. Choice C is incorrect as lipids do not necessarily contain zinc; this is more common in proteins. Choice D is incorrect because lipids do not form long proteins; proteins are made up of amino acids.

Correct Answer: B

Rationale: The correct answer is B: Cell membrane. The cell membrane is a selectively permeable barrier that protects the cell, regulates communication with the external environment, and allows substances to enter and exit the cell. It is composed of a phospholipid bilayer with embedded proteins that facilitate transport and signaling. The other choices are incorrect because: A: Nucleus - The nucleus houses the cell's genetic material and is responsible for controlling cell activities, but it does not directly contribute to protection or substance passage. C: Endoplasmic reticulum - The ER is involved in protein synthesis and lipid metabolism, but it does not have a primary role in protection or communication. D: Cytoplasm - The cytoplasm is the fluid-filled region of the cell where organelles are suspended, but it does not play a direct role in protection or communication at the cell's boundary.

Correct Answer: C

Rationale: The correct answer is C: Hydrogen. Water molecules are bonded to each other through hydrogen bonds. In a water molecule, oxygen is more electronegative than hydrogen, creating a partial negative charge on oxygen and a partial positive charge on hydrogen. These opposite charges allow hydrogen bonding to occur between water molecules, where the partially positive hydrogen atom of one molecule is attracted to the partially negative oxygen atom of another molecule. This type of bond is weaker than covalent bonds but crucial for the unique properties of water, such as high surface tension and cohesion. Summary of other choices: A: Ionic - Water molecules do not form ionic bonds with each other. B: Covalent - While water molecules are held together by covalent bonds within the molecule itself, they are not bonded to each other through covalent bonds. D: Molecular - This choice is vague and does not accurately describe the specific type of bonding between water molecules.

Correct Answer: C

Rationale: The correct answer is C: Synthesize proteins. Ribosomes are responsible for protein synthesis in the cell by translating mRNA into specific amino acid sequences. They are composed of rRNA and protein subunits. Ribosomes do not break down cellular waste (A), organize cellular division (B), or provide cellular structure (D). Cellular waste breakdown is typically performed by lysosomes, cellular division is organized by the centrosome, and cellular structure is maintained by the cytoskeleton.

Correct Answer: A

Rationale: The correct answer is A: two diploid cells. During mitosis in humans, a single diploid cell divides into two identical diploid cells. This process ensures that each new cell receives a complete set of chromosomes, maintaining the same genetic information. This is essential for growth, repair, and maintenance of tissues in the body. Choices B, C, and D are incorrect because mitosis results in the production of genetically identical diploid cells, not haploid cells or additional copies of diploid cells. Haploid cells are produced through meiosis, not mitosis.