Each nucleotide is composed of
one phosphate, one nitrogenous base, one sugar.
one phosphate, one nitrogenous base, two sugars.
two phosphates, one nitrogenous base, two sugars.
one phosphate, two nitrogenous bases, one sugar.
The Correct Answer is A
A. one phosphate, one nitrogenous base, one sugar: A nucleotide, the basic building block of nucleic acids, consists of a phosphate group, a five-carbon sugar (deoxyribose in DNA or ribose in RNA), and a single nitrogenous base (adenine, thymine, cytosine, guanine, or uracil in RNA). The phosphate forms the backbone of the nucleic acid chain, the sugar provides structural support, and the base carries the genetic information.
B. one phosphate, one nitrogenous base, two sugars: Nucleotides contain only one sugar, not two. Including two sugars would create a structure inconsistent with the polymerization and base-pairing rules of nucleic acids.
C. two phosphates, one nitrogenous base, two sugars: This composition is incorrect because a nucleotide contains one phosphate and one sugar. Two phosphates are only present in nucleoside diphosphates (like ADP), which are energy carriers, not in standard nucleotides forming DNA or RNA strands.
D. one phosphate, two nitrogenous bases, one sugar: Each nucleotide contains only one nitrogenous base. Having two bases would disrupt proper base pairing and the linear structure required for DNA and RNA strands.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
If a bacterial molecule uses SO₄²⁻ (sulfate) as its final electron acceptor, the process is anaerobic, not aerobic. Aerobic respiration specifically requires oxygen (O₂) as the terminal electron acceptor in the electron transport chain. In contrast, certain bacteria can perform anaerobic respiration, using alternative electron acceptors such as sulfate, nitrate, or carbon dioxide. In sulfate-reducing bacteria, sulfate is reduced to hydrogen sulfide (H₂S) during energy production, allowing ATP synthesis in the absence of oxygen. Therefore, using sulfate as the terminal electron acceptor defines an anaerobic metabolic pathway.
Correct Answer is A
Explanation
A. mRNA: During transcription, a segment of DNA is used as a template to synthesize messenger RNA (mRNA). RNA polymerase binds to the DNA, unwinds the double helix, and assembles a complementary RNA strand. This mRNA carries the genetic code from the nucleus (or nucleoid in prokaryotes) to the ribosome for translation into protein.
B. Protein: Proteins are not produced during transcription. Protein synthesis occurs during translation, where ribosomes read the mRNA sequence and assemble amino acids into a polypeptide chain.
C. Polypeptide: Polypeptides are the direct product of translation, not transcription. Transcription only generates the RNA template needed to guide the sequential assembly of amino acids into a functional polypeptide.
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