why is dna important for the metabolic activities of the cell

HESI A2

HESI A2 Practice Test Biology

1. Why is DNA important for the metabolic activities of the cell?

A. It initiates cellular mitosis.
B. It provides cell wall stability.
C. It increases glucose absorption.
D. It controls the synthesis of enzymes.

Correct answer: D

Rationale: DNA is important for the metabolic activities of the cell because it controls the synthesis of enzymes. Enzymes are essential for catalyzing metabolic reactions in the cell. Choices A, B, and C are incorrect because DNA is not directly involved in cellular mitosis, cell wall stability, or glucose absorption.

2. What type of transport moves substances across the cell membrane using energy?

A. Passive Transport
B. Active Transport
C. Facilitated Diffusion
D. Osmosis

Correct answer: B

Rationale: The correct answer is B: Active Transport. Active transport moves substances across the cell membrane by utilizing energy from the cell, typically in the form of ATP. This process allows the cell to move molecules against their concentration gradient, requiring energy expenditure. Choices A, C, and D are incorrect because passive transport does not require energy input, facilitated diffusion involves the assistance of proteins but does not directly use energy, and osmosis is the diffusion of water molecules specifically, not substances, across a selectively permeable membrane.

3. Why is homeostasis necessary?

A. It maintains temperature
B. It maintains pH
C. It maintains glucose levels
D. All of the above

Correct answer: D

Rationale: Homeostasis is necessary because it ensures the maintenance of a stable, relatively constant internal environment. This includes regulating various factors such as temperature, pH levels, and glucose levels to support optimal bodily functions and overall health. Choices A, B, and C are all correct as they represent key aspects of homeostasis that contribute to maintaining the body's internal balance.

4. Which of the following is necessary for cell diffusion?

A. water
B. membrane
C. ATP
D. gradient

Correct answer: D

Rationale: The correct answer is 'gradient.' In cell diffusion, substances move from an area of high concentration to an area of low concentration, driven by the concentration gradient. This process does not require water, membrane, or ATP specifically. Water can aid in the movement of substances, but it is not necessary for diffusion itself. The membrane is involved in regulating diffusion but is not a requirement for the process. ATP is not directly involved in simple diffusion processes; instead, it is more related to active transport mechanisms. Therefore, the concentration gradient is essential for cell diffusion to occur.

5. How is the plasma membrane arranged?

A. In a single layer made of proteins
B. In a double layer made of proteins
C. In a single layer of phospholipids
D. In a double layer of phospholipids

Correct answer: D

Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a phospholipid bilayer. This structure consists of two layers of phospholipid molecules with hydrophilic heads facing the exterior and hydrophobic tails facing the interior, providing a semipermeable barrier for the cell. Choice A is incorrect because the plasma membrane is not made of a single layer of proteins. Choice B is incorrect as the double layer is composed of phospholipids, not proteins. Choice C is incorrect as the plasma membrane is not made of a single layer of phospholipids but rather a double layer.