which of the following is a group of three rna nucleotides

HESI RN

Biology Practice Test

1. Which of the following is a group of three RNA nucleotides?

A. A stop codon
B. A codon
C. An anticodon
D. tRNA

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.

2. Which of the following is often referred to as the powerhouse of the cell?

A. Nucleus
B. Chromatin
C. Mitochondria
D. Ribosomes

Correct answer: C

Rationale: Mitochondria are known as the powerhouse of the cell because they generate most of the cell's supply of ATP, which is the energy currency used for various cellular processes. The nucleus (Choice A) is the control center of the cell, housing genetic material. Chromatin (Choice B) is a complex of DNA and proteins within the nucleus. Ribosomes (Choice D) are responsible for protein synthesis and not the primary energy production in the cell.

3. Which of the following serves as the information processing and administrative center of the cell?

A. Golgi apparatus
B. Cytoplasm
C. Nucleus
D. Lysosomes

Correct answer: C

Rationale: The correct answer is C, the nucleus. The nucleus is indeed the information processing and administrative center of the cell as it contains the genetic material (DNA) and is responsible for controlling cellular activities. The Golgi apparatus (Choice A) is involved in processing and packaging proteins, the cytoplasm (Choice B) is the fluid that fills the cell and provides a medium for organelles to be suspended, and lysosomes (Choice D) are responsible for digesting waste materials and foreign invaders. Therefore, the nucleus is the most appropriate choice for the given function.

4. What characteristic of water allows for hydrogen bonding between molecules?

A. Its covalent bonds
B. Its cohesive properties
C. Its high specific heat
D. Its polar nature

Correct answer: D

Rationale: The correct answer is D: Its polar nature. Water is a polar molecule with a partial positive charge on hydrogen atoms and a partial negative charge on oxygen atoms. This polarity allows water molecules to form hydrogen bonds with each other. Choice A, covalent bonds, is incorrect because while water indeed has covalent bonds, they do not directly enable hydrogen bonding. Choice B, cohesive properties, is incorrect as cohesion refers to water's ability to stick to other substances, not the specific characteristic that allows for hydrogen bonding. Choice C, high specific heat, is also incorrect as it refers to water's ability to resist changes in temperature, not its property that leads to hydrogen bonding.

5. What do prokaryotic cells lack in comparison to eukaryotic cells?

A. A defined nucleus and a series of membrane-bound organelles
B. A defined nucleus and no membrane-bound organelles
C. No defined nucleus and a series of membrane-bound organelles
D. No defined nucleus and no membrane-bound organelles

Correct answer: D

Rationale: Prokaryotic cells are characterized by the absence of a defined nucleus and membrane-bound organelles. Choice A is incorrect because prokaryotic cells lack membrane-bound organelles. Choice B is incorrect because prokaryotic cells lack both a defined nucleus and membrane-bound organelles. Choice C is incorrect as prokaryotic cells have no defined nucleus. Therefore, the correct answer is D.