HESI A2 Practice Test Biology

Correct Answer: A

Rationale: The correct answer is A: Mitochondrion and chloroplast. Mitochondria are known as the powerhouse of the cell, producing energy in the form of ATP through cellular respiration. Chloroplasts are responsible for photosynthesis in plant cells, converting sunlight into energy. Nucleus is not involved in energy production but contains genetic material. Lysosomes are involved in digestion and waste removal, not energy production. Therefore, A is correct as both mitochondria and chloroplasts play crucial roles in generating cell energy.

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: B

Rationale: The correct answer is B: red blood cell. Red blood cells do not have a nucleus because during their maturation process, they eject their nucleus to make more space for hemoglobin which carries oxygen. Without a nucleus, red blood cells have more space to efficiently transport oxygen throughout the body. Platelets (A), white blood cells (C), and phagocytes (D) all have nuclei as they are involved in various cellular functions that require genetic material and the ability to replicate.

Correct Answer: B

Rationale: The correct answer is B: oxygen. Oxygen is not a product of the Krebs cycle; it is used as the final electron acceptor in the electron transport chain. Carbon dioxide (A) is a product of the Krebs cycle, produced during decarboxylation reactions. Adenosine triphosphate (ATP) (C) and energy carriers (D) such as NADH and FADH2 are also products of the Krebs cycle, as they are generated through the oxidation of substrates. Oxygen's role is crucial for the efficient functioning of aerobic respiration, but it is not a direct product of the Krebs cycle.

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.