HESI A2 Practice Test Biology

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.

Correct Answer: C

Rationale: The correct answer is C: covalent. In DNA, the bond connecting sugar and phosphate is a covalent bond. This is because covalent bonds involve the sharing of electrons between atoms, which is essential for forming the strong backbone structure of the DNA molecule. Hydrogen bonds (choice A) are important for holding the nitrogenous bases together in the DNA double helix, but they do not connect sugar and phosphate. Ionic bonds (choice B) involve the transfer of electrons between atoms, not sharing, and are not typically found in the structure of DNA. "Overt" (choice D) is not a type of chemical bond and is an incorrect term in this context. Thus, the correct choice is covalent based on the nature of the bond required to connect sugar and phosphate in DNA.

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.

Correct Answer: A

Rationale: The second part of an organism's scientific name is the species. In binomial nomenclature, developed by Carl Linnaeus, the scientific name consists of two parts: the genus and the species. The genus is the broader category that encompasses multiple species, while the species is the specific name unique to that particular organism within the genus. Therefore, the correct answer is A: species. Option B: phylum is incorrect as it is a higher taxonomic rank above the genus and species. Option C: population is incorrect as it refers to a group of organisms of the same species in a particular area. Option D: kingdom is incorrect as it is the highest taxonomic rank, encompassing all living organisms categorized into five kingdoms.

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.