Nokea
Which of the following cell types has no nucleus?
- A. platelet
- B. red blood cell
- C. white blood cell
- D. phagocyte
Correct Answer: B
Rationale: The correct answer is B, red blood cell. In humans, red blood cells do not have a nucleus. This unique feature allows them to have more space to carry oxygen efficiently. Platelets (choice A), white blood cells (choice C), and phagocytes (choice D) all have nuclei. Platelets are cell fragments, while white blood cells and phagocytes are types of immune cells that contain a nucleus for DNA and cellular functions.
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What is the typical result of mitosis in humans?
- A. two diploid cells
- B. two haploid cells
- C. four diploid cells
- D. four haploid cells
Correct Answer: A
Rationale: The correct answer is A: two diploid cells. Mitosis is a type of cell division that results in two daughter cells, each having the same number of chromosomes as the parent cell. In humans, the typical result of mitosis is the formation of two diploid cells, not haploid or four cells. Choice B, two haploid cells, is incorrect because mitosis produces genetically identical diploid cells. Choices C and D, four diploid cells and four haploid cells, respectively, are incorrect as mitosis results in two daughter cells, not four.
What kind of bond connects sugar and phosphate in DNA?
- A. hydrogen
- B. ionic
- C. covalent
- D. overt
Correct Answer: C
Rationale: Sugar and phosphate are indeed connected by covalent bonds in DNA. Covalent bonds involve the sharing of electrons between atoms, which is essential for forming the backbone of the DNA molecule. Hydrogen bonds (Choice A) are important in holding the nitrogenous bases together in the DNA double helix but do not connect sugar and phosphate. Ionic bonds (Choice B) involve the transfer of electrons between atoms and are not the primary bond connecting sugar and phosphate in DNA. 'Overt' (Choice D) is not a type of chemical bond and is an incorrect distractor.
During protein synthesis, what process creates a complementary strand of RNA from a DNA template?
- A. Transcription
- B. Translation
- C. Transformation
- D. Replication
Correct Answer: A
Rationale: The correct answer is 'Transcription.' During protein synthesis, transcription is the process that creates a complementary RNA strand from a DNA template. This process involves the synthesis of mRNA using DNA as a template. Choice B, 'Translation,' is incorrect as it is the process where the genetic code carried by mRNA is decoded to produce a specific polypeptide chain. Choice C, 'Transformation,' is not related to the synthesis of RNA from a DNA template. Choice D, 'Replication,' is the process of copying DNA to produce an identical DNA molecule, not RNA.
Which of the following structures is not directly involved in translation?
- A. tRNA
- B. mRNA
- C. ribosome
- D. DNA
Correct Answer: D
Rationale: The correct answer is 'D: DNA.' DNA is not directly involved in translation, which is the process of synthesizing proteins from mRNA. tRNA carries amino acids to the ribosome, mRNA provides the template for protein synthesis, and ribosomes are the cellular machinery where translation occurs. DNA's main role is in transcription, where it serves as the template for mRNA synthesis, not in translation.
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.