HESI RN
Biology Test
1. Which of the following molecules acts as the genetic code's messenger?
- A. RNA
- B. Proteins
- C. DNA
- D. Carbohydrates
Correct answer: A
Rationale: The correct answer is RNA. RNA, particularly mRNA, serves as the messenger that carries genetic information from DNA to the ribosome, where proteins are synthesized. Proteins (choice B) are not the genetic code's messenger; they are synthesized based on the information carried by RNA. DNA (choice C) stores the genetic information but does not directly act as the messenger. Carbohydrates (choice D) are not involved in transmitting genetic information.
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. What is the liquid found inside the cell?
- A. Plasma membrane
- B. Cilia
- C. Cytoplasm
- D. Cytosol
Correct answer: D
Rationale: The correct answer is D, Cytosol. Cytosol is the liquid component of the cytoplasm where various cellular processes occur. Choices A, B, and C are incorrect because the plasma membrane is the outer boundary of the cell, cilia are hair-like structures on the cell surface, and cytoplasm is the jelly-like substance that contains organelles within the cell, not the liquid inside the cell.
4. 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.
5. 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.
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