Biology HESI A2 Practice Test

Correct Answer: D

Rationale: Step-by-step rationale: 1. The head of a phospholipid molecule contains a phosphate group, making it hydrophilic. 2. This hydrophilic head faces outward towards the water in the extracellular or intracellular environment. 3. The hydrophobic tail of the phospholipid faces inward, away from the water. 4. As a result, the head is on the outer side of the phospholipid bilayer, while the tail is on the inner side. 5. Therefore, the correct answer is D (Both A and C) as the head is hydrophilic and on the outer side of the layer. Summary: - Choice A is incorrect as the head of a phospholipid is hydrophilic, not hydrophobic. - Choice B is incorrect as the head is hydrophilic, not hydrophobic. - Choice C is incorrect as the head is on the outer side, not the inner side, of the phospholip

Correct Answer: A

Rationale: Enzymes can catalyze reactions by lowering the activation energy required for the reaction to occur, thus increasing the reaction rate. This is achieved through the formation of enzyme-substrate complexes. Inhibition refers to the process of preventing enzyme activity, which is contrary to the function of enzymes. Stopping reactions is not the role of enzymes. Therefore, the correct answer is A: Catalyze.

Correct Answer: B

Rationale: The correct answer is B because the Krebs cycle involves the oxidation of acetyl CoA, a product of glycolysis, leading to the production of NADH and FADH2. Choice A is incorrect because the proteins are not directly involved in the Krebs cycle. Choice C is incorrect because protons are not passed along a gradient in the Krebs cycle; they are used in the electron transport chain to produce ATP. Choice D is incorrect because the Krebs cycle is not known as the glycolic acid cycle; glycolysis is the pathway that produces glycolic acid.

Correct Answer: C

Rationale: The correct answer is C: Producing blood. The skeletal system does not produce blood; that is the function of the bone marrow within the bones. The other choices are functions of the skeletal system: A) Providing shape and form by supporting soft tissues, B) Supporting and protecting the body by providing structure and protecting internal organs, D) Storing vitamins like calcium and phosphorus for bone health. Thus, option C is the correct answer as it does not directly relate to the functions of the skeletal system.

Correct Answer: C

Rationale: The correct answer is C because molecules move from areas of high concentration to low concentration through a process called passive diffusion, which does not require energy. This movement occurs to reach equilibrium. Choice A is incorrect as some molecules can pass through cell membranes using channels or transporters. Choice B is incorrect because molecules move from high to low concentration in passive transport. Choice D is incorrect because molecules are constantly moving due to various forces.