Biology Practice Test

Correct Answer: B

Rationale: The correct answer is B - A codon. A codon is a sequence of three RNA nucleotides that specifies a particular amino acid or a stop signal during protein synthesis. Choice A, a stop codon, is a sequence of three nucleotides that signals the termination of protein synthesis. Choice C, an anticodon, is a group of three nucleotides found in tRNA that pairs with the complementary codon in mRNA. Choice D, tRNA, stands for transfer RNA, which is a type of RNA that carries amino acids to the ribosome during protein synthesis.

Correct Answer: D

Rationale: The rough endoplasmic reticulum is studded with ribosomes, not microvilli, mitochondria, or lysosomes. Ribosomes are responsible for protein synthesis, making them an essential component of the rough endoplasmic reticulum.

Correct Answer: B

Rationale: The correct answer is B: Smooth endoplasmic reticulum. The liver contains a high amount of smooth endoplasmic reticulum because it plays a significant role in detoxification processes, such as the synthesis of detoxifying enzymes and lipids. Choice A (Rough endoplasmic reticulum) is incorrect because the rough endoplasmic reticulum is more involved in protein synthesis and processing. Choice C (Mitochondria) is incorrect as mitochondria are primarily responsible for energy production. Choice D (Lysosomes) is incorrect because lysosomes are organelles involved in intracellular digestion and waste removal, not specifically related to detoxification.

Correct Answer: A

Rationale: The correct answer is A: Nucleic acids. DNA and RNA are both types of nucleic acids, which are fundamental biological molecules responsible for storing and transmitting genetic information. Choice B, Proteins, are not subunits of DNA and RNA but are composed of amino acids. Carbohydrates, choice C, are another type of biological molecule involved in energy storage and structural support, not subunits of DNA and RNA. Lipids, choice D, are a diverse group of molecules that include fats, oils, and steroids, but they are not subunits of DNA and RNA.

Correct Answer: A

Rationale: The cellular membrane is composed of a phospholipid bilayer with cholesterol, proteins, and glycoproteins distributed throughout. Nucleic acids are not found within the cellular membrane. Cholesterol helps maintain membrane fluidity, while proteins and glycoproteins play important roles in cell signaling, transport, and structural support.