how is the plasma membrane arranged

HESI A2

HESI A2 Biology Practice Test

1. 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.

2. Why do gardeners sometimes use salt to get rid of slugs?

A. The salt moves from the exterior into the slug’s body.
B. The salt causes water in the slug to move outward.
C. The salt and slug slime merge to form a new compound.
D. The salt’s corrosiveness breaks down the slug’s cell walls.

Correct answer: D

Rationale: Gardeners use salt to get rid of slugs because salt is corrosive and breaks down the slug's cell walls. When the slug comes into contact with salt, the salt draws moisture out of the slug's body, causing dehydration and ultimately leading to the slug's death. Choices A, B, and C are incorrect because the primary mechanism of salt in eliminating slugs is its corrosive action on the slug's body, not the movement of salt into the slug's body, outward movement of water in the slug, or merging with slug slime to form a new compound.

3. What is the function of decomposition in the carbon cycle?

A. To produce light energy
B. To convert carbon to fuel
C. To release carbon dioxide
D. To store food for consumers

Correct answer: C

Rationale: The correct answer is C: 'To release carbon dioxide.' Decomposition in the carbon cycle involves breaking down dead organic matter into simpler substances. During this process, carbon is released in the form of carbon dioxide back into the atmosphere. This release of carbon dioxide is essential for recycling carbon and making it available for use by living organisms. Choices A, B, and D are incorrect because decomposition does not produce light energy, convert carbon to fuel, or store food for consumers; its primary role is to recycle carbon through the release of carbon dioxide.

4. How do green plants use nitrates in the nitrogen cycle?

A. To synthesize proteins
B. To store food
C. To decompose ammonia
D. To break down nitrites

Correct answer: A

Rationale: Green plants use nitrates in the nitrogen cycle to synthesize proteins. Nitrogen is an essential component of amino acids, which are the building blocks of proteins. Plants take up nitrates from the soil through their roots and incorporate nitrogen into their proteins through the process of protein biosynthesis. This helps in their growth, development, and overall health. Choice B, 'To store food,' is incorrect because nitrates are primarily used for protein synthesis, not food storage. Choice C, 'To decompose ammonia,' is incorrect as plants do not decompose ammonia but rather utilize it through nitrification. Choice D, 'To break down nitrites,' is incorrect as plants typically convert nitrites into nitrates through a process called nitrate assimilation for protein synthesis.

5. What is the process of cell division that results in two daughter cells with identical genetic material?

A. Mitosis
B. Meiosis
C. Binary Fission
D. Budding

Correct answer: A

Rationale: The correct answer is A, Mitosis. Mitosis is the process of cell division in which a cell divides and produces two daughter cells that are genetically identical to the parent cell. Choice B, Meiosis, is a type of cell division that produces gametes with half the number of chromosomes. Choice C, Binary Fission, is a form of asexual reproduction in single-celled organisms. Choice D, Budding, is a form of asexual reproduction where a new organism develops from an outgrowth or bud on the parent.