Biology HESI A2 Practice Test

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: Proteins are the best choice to increase muscle mass and strength because they are essential for muscle repair and growth. Proteins are made up of amino acids, which are the building blocks of muscles. Consuming enough protein provides the body with the necessary nutrients to repair and build muscle tissue. Carbohydrates are primarily for energy, lipids are for long-term energy storage, and nucleic acids are not directly involved in muscle growth. Therefore, proteins are the most suitable option for athletes looking to increase muscle mass and strength.

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: D

Rationale: Homeostasis is necessary to maintain stable internal conditions in the body for optimal function. A: Temperature regulation ensures enzymes work efficiently. B: pH balance is crucial for enzyme activity and cell function. C: Glucose levels impact energy production. D: All choices are essential for overall health and function, making D the correct answer. Maintaining just one aspect wouldn't be enough to support the body's complex processes.

Correct Answer: A

Rationale: Adenine is a purine base because it has a double-ring structure, which is a characteristic of purines. It pairs with thymine in DNA and uracil in RNA. Cytosine, thymine, and guanine are pyrimidines, which have a single-ring structure. Therefore, the correct answer is A. Cytosine, thymine, and guanine are incorrect choices as they are pyrimidines.