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: 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: ATP. ATP (adenosine triphosphate) is the primary molecule responsible for storing and transferring energy in cells through its high-energy phosphate bonds. Glucose (choice A) is a source of energy but not a storage molecule. Fatty acids (choice C) are primarily used for long-term energy storage. Starch (choice D) is a polysaccharide used for energy storage in plants, but ATP is the main energy currency in all cells for immediate use.

Correct Answer: C

Rationale: The correct answer is C: Supply electrons in the light reactions. In photosynthesis, water molecules are split during the light reactions of photosynthesis, releasing electrons that are used to drive the electron transport chain. This process generates ATP and NADPH, which are essential for the synthesis of glucose in the Calvin cycle. Water does not combine with carbon dioxide (A), absorb light energy (B), or transport hydrogen ions in the dark reactions (D) during photosynthesis.

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.