A patient with an acute viral infection undergoes electron microscopy of the pathogen, revealing genetic material enclosed within a protective protein structure, with some virions also displaying an outer lipid layer derived from the host cell membrane. Which statement best describes the basic structure of a virus?
A virus consists of a cell wall, ribosomes, and cytoplasm
A virus consists of a nucleic acid genome surrounded by a protein capsid and sometimes a lipid envelope
A virus contains a nucleus and membrane-bound organelles
A virus is composed entirely of lipopolysaccharide and protein
The Correct Answer is B
A. A virus consists of a cell wall, ribosomes, and cytoplasm: Viruses are acellular particles and do not possess cellular structures such as a cell wall, ribosomes, or cytoplasm. These components are characteristic of prokaryotic or eukaryotic cells. Viruses lack metabolic machinery and depend entirely on host cells for protein synthesis and energy production.
B. A virus consists of a nucleic acid genome surrounded by a protein capsid and sometimes a lipid envelope: The fundamental structure of a virus includes either DNA or RNA as its genetic material enclosed within a protein capsid. Some viruses also possess a lipid envelope derived from the host cell membrane during budding.
C. A virus contains a nucleus and membrane-bound organelles: A nucleus and organelles such as mitochondria or endoplasmic reticulum are defining features of eukaryotic cells. Viruses lack internal cellular organization and do not contain membrane-bound organelles.
D. A virus is composed entirely of lipopolysaccharide and protein: Lipopolysaccharide is a component of the outer membrane of Gram-negative bacteria, not viruses. Viral structure is defined by nucleic acid and a protein capsid, with some viruses also containing a lipid envelope derived from host membranes.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Spore-forming rods with a thick cell wall, such as Clostridioides difficile, are classified as gram-positive bacteria. Their thick peptidoglycan layer retains the crystal violet stain during the Gram-staining process, causing them to appear purple under a microscope. The spore-forming ability allows these bacteria to survive harsh conditions, including exposure to antibiotics, which can disrupt normal gut flora. The combination of thick peptidoglycan and spore formation is characteristic of gram-positive bacilli. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides. They do not retain the crystal violet stain and instead appear pink after counterstaining with safranin. Spore formation is not a typical feature of gram-negative organisms.
Correct Answer is A
Explanation
Pili, also called sex pili, are hair-like appendages on the surface of many bacteria that are longer than fimbriae and play a key role in bacterial conjugation. During conjugation, a donor bacterium uses a pilus to attach to a recipient cell and transfer genetic material, typically plasmids, which can carry genes for antibiotic resistance or other traits. Fimbriae, in contrast, are shorter and primarily function in adhesion to surfaces or host tissues, not in genetic exchange. The structural and functional distinction between pili and fimbriae allows bacteria to both attach to environments and share genetic information for survival and adaptation.
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