Nokea
Protein synthesis begins with a process known as transcription. Where does this process occur?
- A. In the cytoplasm
- B. In the nuclear envelope
- C. In the ribosome unit
- D. In the nucleus
Correct Answer: D
Rationale: The correct answer is D: In the nucleus. Transcription, the initial step of protein synthesis, takes place in the nucleus where DNA is transcribed into mRNA. This mRNA then leaves the nucleus and enters the cytoplasm where translation occurs on the ribosomes. Choices A, B, and C are incorrect because transcription specifically occurs in the nucleus, not in the cytoplasm, nuclear envelope, or ribosome unit.
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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).
During which stage of mitosis do the chromosomes gather on either side of the separating cell?
- A. Metaphase
- B. Telophase
- C. Anaphase
- D. Prophase
Correct Answer: B
Rationale: The correct answer is B, Telophase. During telophase, the chromosomes gather at opposite poles of the cell as the nuclear envelopes start to form around them, indicating the end of cell division. Choices A, C, and D are incorrect because during metaphase, the chromosomes align in the middle of the cell; in anaphase, the chromosomes separate and move towards opposite poles; and in prophase, the chromosomes condense and the nuclear envelope breaks down, respectively.
What is the main objective of the translation stage of protein synthesis?
- A. To produce amino acids
- B. To produce nucleotides
- C. To produce fatty acids
- D. To produce proteins
Correct Answer: D
Rationale: The main objective of the translation stage of protein synthesis is to produce proteins. During translation, ribosomes decode mRNA sequences to synthesize proteins by linking amino acids together. Choice A, 'To produce amino acids,' is incorrect as amino acids are the building blocks of proteins and are not produced during translation. Choices B and C, 'To produce nucleotides' and 'To produce fatty acids,' are also incorrect as these molecules are not the direct products of the translation stage of protein synthesis.
What function does cholesterol, a phospholipid, serve within the cell membrane?
- A. It builds up fats to make the structure more flexible
- B. It allows protein channels to form
- C. It makes the structure very rigid and impermeable
- D. It stabilizes the membrane structure
Correct Answer: D
Rationale: Cholesterol helps to maintain the fluidity and stability of the cell membrane by fitting between the phospholipid molecules. Choice A is incorrect because cholesterol does not build up fats in the cell membrane. Choice B is incorrect as protein channels are formed by proteins, not cholesterol. Choice C is incorrect as cholesterol actually helps regulate the fluidity of the membrane, making it less rigid and more permeable.
Where can ribosomes be found inside a cell?
- A. Attached to the endoplasmic reticulum (ER) and in the cytoplasm
- B. Within the cellular membrane
- C. Attached to the Golgi apparatus and in the cytoplasm
- D. Within the nucleus
Correct Answer: A
Rationale: Ribosomes can be found attached to the endoplasmic reticulum (ER) or free-floating in the cytoplasm. The correct answer is A because ribosomes are responsible for synthesizing proteins and are commonly found on the ER or in the cytoplasm. Choice B is incorrect because ribosomes are not typically located within the cellular membrane. Choice C is incorrect as ribosomes are not attached to the Golgi apparatus; instead, they are involved in protein synthesis. Choice D is incorrect as ribosomes are not found within the nucleus but rather in the cytoplasm or attached to the ER.