Nokea
Which of the following organelles are responsible for producing cell energy?
- A. Mitochondrion and chloroplast
- B. Mitochondrion and nucleus
- C. Chloroplast and nucleus
- D. Chloroplast and lysosome
Correct Answer: A
Rationale: The correct answer is A: Mitochondrion and chloroplast. Mitochondria and chloroplasts are the organelles responsible for producing cell energy through cellular respiration and photosynthesis, respectively. Choice B is incorrect because the nucleus is not involved in energy production. Choice C is incorrect as the nucleus is not an organelle that produces energy. Choice D is incorrect as lysosomes function in digesting waste materials, not in energy production.
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What happens during the S phase of the cell cycle?
- A. Chromosomes are duplicated.
- B. Cell growth occurs.
- C. DNA is synthesized.
- D. DNA is destroyed.
Correct Answer: A
Rationale: During the S phase of the cell cycle, chromosomes are duplicated. This is a critical step in cell division as each chromosome is replicated to ensure that the resulting daughter cells receive an identical set of genetic information. Choices B, C, and D are incorrect because cell growth primarily occurs in the G1 phase, DNA synthesis happens during the S phase, and DNA destruction does not occur during any phase of the cell cycle.
What is the role of tRNA during protein synthesis?
- A. Carries amino acids to the ribosome
- B. Links nucleotides together
- C. Copies DNA sequences
- D. Replicates genetic material
Correct Answer: A
Rationale: During protein synthesis, tRNA plays the crucial role of carrying amino acids to the ribosome. This process ensures that the correct amino acids are brought to the ribosome according to the mRNA sequence. Choice B, linking nucleotides together, refers to the role of RNA polymerase in transcription, not tRNA. Choice C, copying DNA sequences, is the function of DNA polymerase during DNA replication, while choice D, replicating genetic material, is an overarching function of DNA replication, not specific to tRNA's role in protein synthesis.
How many different types of nucleotides are there in DNA?
- A. one
- B. two
- C. four
- D. eight
Correct Answer: C
Rationale: The correct answer is 'C: four.' DNA is composed of four different types of nucleotides: adenine, thymine, guanine, and cytosine. These nucleotides pair up in specific combinations to form the genetic code. Choices 'A: one,' 'B: two,' and 'D: eight' are incorrect because DNA consists of a set of four distinct nucleotides, not one, two, or eight.
Which of the following is not found within a bacterial cell?
- A. mitochondria
- B. DNA
- C. vesicles
- D. ribosome
Correct Answer: A
Rationale: The correct answer is A: mitochondria. Mitochondria are not found in bacterial cells. Bacterial cells lack membrane-bound organelles like mitochondria, which are commonly found in eukaryotic cells. Choices B, C, and D are all components that can be found within a bacterial cell. Bacterial cells contain DNA as their genetic material, vesicles for various cellular functions, and ribosomes for protein synthesis. Therefore, the presence of mitochondria is the distinguishing factor that is not found in bacterial cells, making option A the correct answer.
During which phase is the chromosome number reduced from diploid to haploid?
- A. S phase
- B. interphase
- C. mitosis
- D. meiosis I
Correct Answer: D
Rationale: The correct answer is 'meiosis I.' During meiosis I, the chromosome number is reduced from diploid to haploid through two rounds of division. Choice A ('S phase') is incorrect as the S phase is part of the cell cycle where DNA is replicated. Choice B ('interphase') is also incorrect as interphase is the phase where the cell prepares for division. Choice C ('mitosis') is incorrect as mitosis is a process where a diploid cell divides to produce two identical diploid daughter cells, maintaining the chromosome number.