which of the following molecules is an important component of the plasma membrane

HESI A2

HESI A2 Practice Test Biology

1. Which of the following molecules is an important component of the plasma membrane?

A. Phospholipids
B. Steroids
C. Sugars
D. Amino acids

Correct answer: A

Rationale: Phospholipids are indeed a crucial component of the plasma membrane. They have a unique structure with hydrophilic heads and hydrophobic tails, which allows them to form the lipid bilayer of the membrane. Steroids, sugars, and amino acids are not primary components of the plasma membrane. Steroids are a different type of lipid, sugars are often found in glycoproteins on the membrane surface, and amino acids are the building blocks of proteins, some of which are membrane proteins, but not the membrane itself.

2. Which organelle is responsible for organizing protein synthesis?

A. Nucleus
B. Ribosome
C. Lysosome
D. Vacuole

Correct answer: B

Rationale: The correct answer is B: Ribosome. Ribosomes are responsible for organizing protein synthesis by assembling amino acids. They are the cellular machinery where proteins are synthesized. The other choices, such as the nucleus, lysosome, and vacuole, do not directly participate in protein synthesis. The nucleus contains DNA and controls cell activities, the lysosome is involved in digestion and waste removal, and the vacuole is responsible for storage and maintaining cell turgor pressure.

3. Which two bases are purines?

A. Adenine (A)
B. Cytosine (C)
C. Thymine (T)
D. Guanine (G)

Correct answer: A

Rationale: Adenine (A) and guanine (G) are the two bases that are purines. Purines are characterized by a double-ring structure containing two carbon rings, distinguishing them from pyrimidines. Adenine and guanine are purines because they possess this unique double-ring structure. Therefore, choices A and D, adenine and guanine, respectively, are the correct answers. Choices B and C, cytosine and thymine, are pyrimidines and do not exhibit the double-ring structure characteristic of purines.

4. Which of the following is an example of human error in an experiment?

A. an imperfectly calibrated scale
B. contaminating a sterile sample by breathing on it
C. a draft in the laboratory slightly changing the temperature of a liquid
D. failure to account for wind speed when measuring distance traveled

Correct answer: B

Rationale: Contaminating a sterile sample by breathing on it is an example of human error in an experiment because it involves an action directly caused by the researcher that compromises the integrity of the sample. Breathing on a sterile sample introduces external contaminants that can affect the results. Choices A, C, and D involve factors not directly under the researcher's control or are technical errors that do not involve direct human actions.

5. What is the process by which cells divide to form two identical daughter cells?

A. Mitosis
B. Meiosis
C. Binary Fission
D. Cellular Division

Correct answer: A

Rationale: The correct answer is A, Mitosis. Mitosis is the process in which a cell divides to form two identical daughter cells. Choice B, Meiosis, is a type of cell division that results in four non-identical daughter cells with half the number of chromosomes. Choice C, Binary Fission, is a form of asexual reproduction used by prokaryotic organisms. Choice D, Cellular Division, is a general term that encompasses various processes of cell division, but specifically, mitosis refers to the division resulting in two identical daughter cells.