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 responsible for the synthesis of carbohydrates, lipids, and steroid hormones?

A. Smooth endoplasmic reticulum (ER)
B. Rough endoplasmic reticulum (ER)
C. Golgi apparatus
D. Ribosomes

Correct answer: A

Rationale: The smooth endoplasmic reticulum (ER) is the correct answer. It is responsible for the synthesis of lipids, including steroids, and also plays a role in carbohydrate metabolism. The rough endoplasmic reticulum (ER) is involved in protein synthesis and processing, not lipid or carbohydrate synthesis. The Golgi apparatus is responsible for modifying, sorting, and packaging of proteins and lipids, but not for their synthesis. Ribosomes are the cellular organelles responsible for protein synthesis, not lipid or carbohydrate synthesis.

3. Protein synthesis begins with a process known as transcription. What is produced during this process?

A. A codon
B. A DNA helix
C. A DNA strand
D. An RNA strand

Correct answer: D

Rationale: The correct answer is D: An RNA strand. During transcription, the DNA template is used to produce an RNA strand, not a codon, DNA helix, or another DNA strand. A codon is a sequence of nucleotides that specifies a particular amino acid during translation, not produced during transcription. A DNA helix refers to the double-stranded structure of DNA, which is not produced during transcription. Another DNA strand is not produced during transcription since the process involves creating an RNA copy of a specific gene.

4. Which of the following is not one of the four nitrogenous bases that make up the DNA structure?

A. Adenine
B. Guanine
C. Uracil
D. Thymine

Correct answer: C

Rationale: The correct answer is C: Uracil. Uracil is found in RNA, not DNA. The four nitrogenous bases in DNA are adenine, thymine, cytosine, and guanine. Choice A, Adenine, is a nitrogenous base in DNA. Choice B, Guanine, is another nitrogenous base in DNA. Choice D, Thymine, is also one of the four nitrogenous bases in DNA. Therefore, the correct answer is Uracil (Choice C).

5. What is the most important function of carbohydrates?

A. Store and provide energy for the body
B. Create amino acids
C. Maintain body temperature
D. Insulate body organs against shock

Correct answer: A

Rationale: The most important function of carbohydrates is to store and provide energy for the body through metabolic processes. Carbohydrates are broken down into glucose, which is used as the primary source of energy for various cellular functions. Choice B is incorrect because amino acids are the building blocks of proteins, not directly created by carbohydrates. Choice C is incorrect as the regulation of body temperature is primarily controlled by mechanisms such as sweating and shivering, not carbohydrates. Choice D is incorrect as insulation of body organs against shock is mainly provided by adipose tissue, not carbohydrates.