A patient who recently immigrated from a rural area presents with anemia and abdominal discomfort. Stool examination reveals large, multicellular parasitic organisms. Which statement best describes helminths?

A. Glycocalyx: The glycocalyx is a sticky, gelatinous layer found external to the cell wall in some bacteria and eukaryotic cells. It is primarily composed of polysaccharides and sometimes proteins. This structure functions in adherence to surfaces, protection against desiccation, and evasion of host immune responses, making it essential for colonization and virulence in pathogenic microbes.

B. Capsule: A capsule is a well-organized, dense form of glycocalyx that surrounds certain bacterial cells. While all capsules are glycocalyx, not all glycocalyx is a capsule; the term “capsule” specifically refers to a structured, tightly bound layer that provides enhanced protection and virulence.

C. Membrane: The membrane, including the plasma or cytoplasmic membrane, is a lipid bilayer that controls selective permeability and transport. It is not the sticky, gelatinous external layer.

D. Viroid: A viroid is an infectious, small circular RNA molecule that infects plants. It is unrelated to cellular coatings or structural layers and does not consist of polysaccharides or proteins.

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.