what function does cholesterol a phospholipid serve within the cell membrane

HESI RN

Biology Practice Test

1. What function does cholesterol, a phospholipid, serve within the cell membrane?

A. It builds up fats to make the structure more flexible
B. It allows protein channels to form
C. It makes the structure very rigid and impermeable
D. It stabilizes the membrane structure

Correct answer: D

Rationale: Cholesterol helps to maintain the fluidity and stability of the cell membrane by fitting between the phospholipid molecules. Choice A is incorrect because cholesterol does not build up fats in the cell membrane. Choice B is incorrect as protein channels are formed by proteins, not cholesterol. Choice C is incorrect as cholesterol actually helps regulate the fluidity of the membrane, making it less rigid and more permeable.

2. The cellular membrane contributes to all except which of the following?

A. Cell energy production
B. Cell permeability
C. Cell communication
D. Cell protection

Correct answer: A

Rationale: The cellular membrane is involved in regulating cell permeability, communication, and protection. However, it is not directly involved in energy production. Choice A is the correct answer because the cellular membrane does not produce energy; instead, it regulates the passage of molecules in and out of the cell. Choices B, C, and D are incorrect because the cell membrane plays key roles in controlling what enters and exits the cell, facilitating communication between cells, and providing structural support and protection to the cell.

3. In meiosis, the chromosome number is reduced from:

A. 46 to 23
B. 46 to 33
C. 28 to 14
D. 24 to 12

Correct answer: A

Rationale: The correct answer is A: "46 to 23." In meiosis, the chromosome number is reduced by half to form gametes for sexual reproduction. In humans, where the diploid chromosome number is 46, meiosis results in haploid cells with 23 chromosomes. Choices B, C, and D are incorrect because they do not represent the correct reduction in chromosome number during meiosis.

4. What is the primary method of asexual reproduction used by most bacteria?

A. Meiosis
B. Mitosis
C. Binary fission
D. Interphase

Correct answer: C

Rationale: The correct answer is C: Binary fission. This is the main process through which most bacteria reproduce asexually. During binary fission, a single cell divides into two identical cells, each containing a copy of the genetic material. Choices A and B, meiosis and mitosis, are processes involved in sexual reproduction and are not used by bacteria for asexual reproduction. Choice D, interphase, is a stage of the cell cycle where the cell prepares for division and is not a method of reproduction.

5. A water molecule contains two types of atoms that are covalently bonded. Which of the following makes up a water molecule?

A. One hydrogen atom and one oxygen atom
B. One hydrogen atom and two oxygen atoms
C. Two hydrogen atoms and two oxygen atoms
D. Two hydrogen atoms and one oxygen atom

Correct answer: D

Rationale: The correct answer is D: Two hydrogen atoms and one oxygen atom. A water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom. This forms a stable structure known as H2O. Choice A is incorrect as water molecule contains two hydrogen atoms. Choices B and C are incorrect as they do not reflect the correct composition of a water molecule.