HESI A2 Practice Test Biology

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: 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: 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: D

Rationale: The correct answer is D because DNA controls the synthesis of enzymes, which are essential for carrying out metabolic activities in the cell. Enzymes are biological catalysts that regulate chemical reactions in the cell. DNA contains the genetic information needed to produce specific enzymes through the process of transcription and translation. Enzymes play a crucial role in breaking down nutrients, synthesizing molecules, and regulating metabolic pathways. A: DNA does not initiate cellular mitosis; that is controlled by other molecules. B: DNA is not responsible for providing cell wall stability; that is primarily the role of the cell wall structure itself. C: DNA is not directly involved in increasing glucose absorption; that is regulated by other mechanisms such as insulin signaling.

Correct Answer: C

Rationale: The correct answer is C, fermentation and cellular respiration, because both are catabolic pathways that lead to cellular energy production. Fermentation occurs in the absence of oxygen, producing a small amount of ATP. Cellular respiration, on the other hand, occurs in the presence of oxygen and is a more efficient process, producing a significantly higher amount of ATP. Choices A, B, and D are incorrect because internal respiration, external respiration, and anaerobic respiration do not directly lead to cellular energy production through catabolic pathways.