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. What happens to messenger RNA when it reaches the cytoplasm?

A. It attaches to a ribosome.
B. It unzips, exposing nitrogen bases.
C. It pairs with the DNA bases.
D. It pulls free of the DNA strand.

Correct answer: A

Rationale: Messenger RNA (mRNA) carries genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm. When mRNA reaches the cytoplasm, it attaches to a ribosome. The ribosome functions as the site for protein synthesis through translation, where the genetic code carried by mRNA is read and translated into a specific sequence of amino acids. Choices B, C, and D are incorrect because mRNA does not unzip, expose nitrogen bases, pair with DNA bases, or pull free of the DNA strand in the cytoplasm. The primary function of mRNA in the cytoplasm is to serve as a template for protein synthesis by binding to ribosomes.

3. The scientific name for a house cat is Felis catus. This indicates the house cat’s _ and _.

A. kingdom; family
B. order; subspecies
C. phylum; class
D. genus; species

Correct answer: D

Rationale: The scientific name for an organism consists of its genus and species. In this case, 'Felis' refers to the genus, while 'catus' refers to the species, thus indicating the house cat's genus and species as Felis catus. Therefore, the correct answer is 'D.' Choices A, B, and C are incorrect because a scientific name does not include information about the kingdom, family, order, subspecies, phylum, or class of an organism.

4. What is the primary function of the endoplasmic reticulum in a cell?

A. Energy production
B. Protein synthesis
C. Waste removal
D. Transport of materials

Correct answer: D

Rationale: The endoplasmic reticulum's primary function is the transport of materials within the cell. It acts as a network of membranes to assist in the transportation of proteins and other substances throughout the cell. Choice A, 'Energy production,' is incorrect because the endoplasmic reticulum is not directly involved in energy production. Choice B, 'Protein synthesis,' is incorrect as protein synthesis mainly occurs in ribosomes, although the endoplasmic reticulum is involved in modifying and transporting proteins. Choice C, 'Waste removal,' is also incorrect as waste removal is primarily handled by other organelles like lysosomes and peroxisomes.

5. What is the magnification of an ocular lens on a microscope?

A. 4x
B. 10x
C. 40x
D. 100x

Correct answer: B

Rationale: The magnification of an ocular lens on a microscope is typically 10x, which is considered standard for most microscopes. Ocular lenses are designed to magnify the image produced by the objective lens further. Choices A, C, and D are incorrect because they do not represent the standard magnification of an ocular lens. A magnification of 4x, 40x, or 100x would not be typical for an ocular lens in a microscope.