RNA molecules differ from DNA molecules because only RNA
does not have thymine.
has uracil.
All of the choices are correct.
is typically one strand of nucleotides (single stranded)
has ribose.
The Correct Answer is C
A. does not have thymine: DNA contains the nitrogenous base thymine, whereas RNA lacks thymine. Instead, RNA uses uracil in place of thymine during base pairing. Because thymine is absent from RNA molecules, this difference is one of the key biochemical distinctions between RNA and DNA structure.
B. has uracil: RNA contains the nitrogenous base uracil, which pairs with adenine during RNA synthesis and function. In DNA, thymine performs this role instead. The substitution of uracil for thymine is a defining molecular feature that distinguishes RNA nucleotides from DNA nucleotides.
C. All of the choices are correct: Each of the listed statements accurately describes a property unique to RNA compared with DNA. RNA lacks thymine, contains uracil, typically exists as a single-stranded molecule, and contains ribose sugar rather than deoxyribose. Because every option describes a valid structural difference, this is the most accurate answer.
D. is typically one strand of nucleotides (single stranded): RNA molecules are generally single-stranded, allowing them to fold into complex secondary and tertiary structures that support functions such as translation and gene regulation. DNA, in contrast, usually exists as a double-stranded helix with complementary base pairing between strands.
E. has ribose: RNA nucleotides contain ribose sugar, which includes a hydroxyl group on the 2′ carbon of the pentose ring. DNA contains deoxyribose, which lacks this oxygen atom. This chemical difference contributes to RNA being more reactive and less stable than DNA.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. lag phase: The lag phase is the initial period after bacteria are introduced into a new environment. During this phase, cells are metabolically active but not dividing at a significant rate as they adapt to the new conditions. There is little to no increase in cell number, so it does not represent the phase of maximum cell division.
B. exponential (or log) phase: The exponential or log phase is characterized by rapid, logarithmic cell division, where the population doubles at a constant and maximal rate. Nutrients are abundant, waste products are minimal, and environmental conditions are optimal, making this the period of maximum bacterial growth and replication.
C. prophase: Prophase is a stage of eukaryotic mitosis and is not applicable to bacterial growth. Bacteria reproduce through binary fission rather than mitosis, so prophase does not occur in their growth cycle.
D. stationary phase: The stationary phase occurs when the growth rate slows and stabilizes because nutrient depletion and accumulation of waste products limit further cell division. The number of new cells equals the number of dying cells, so this is not the phase of maximal cell division.
E. death phase: The death phase is marked by a decline in the bacterial population due to nutrient exhaustion, toxic accumulation, and unfavorable environmental conditions. Cell death exceeds new cell formation, representing the opposite of maximal growth.
Correct Answer is C
Explanation
A. endergonic: Endergonic reactions require an input of energy to proceed and result in products with higher free energy than the reactants. While some bond-breaking reactions may involve energy input, the hydrolysis of glycosidic bonds is generally exergonic, releasing energy rather than consuming it.
B. metabolic: The term metabolic is broad and refers to all chemical reactions occurring in an organism, including both catabolic and anabolic processes. While glycosidic bond breakage is part of metabolism, this term does not specifically describe the type of reaction.
C. catabolic: Catabolic reactions involve the breakdown of larger, complex molecules into smaller, simpler ones, typically releasing energy that can be used by the cell. Breaking glycosidic bonds in polysaccharides like starch or glycogen releases monosaccharides and energy, classifying this process as catabolic.
D. anabolic: Anabolic reactions are constructive processes in which small molecules are joined to form larger, complex molecules, usually requiring an input of energy. Forming glycosidic bonds to synthesize polysaccharides would be anabolic, but breaking them is the opposite process.
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