b
nucleolus
a
protein capsid
b
nucleolus
c
ribosomes
d
cytosol
nucleolus
a) protein capsid
Protein capsid is found in viruses and not in cells. A protein capsid is the outer protein coat that encloses the genetic material of a virus.
a) Protein Capsid: This is a protective outer covering made up of proteins that encloses the genetic material of a virus. It plays a crucial role in protecting the genetic material from degradation and facilitating its entry into host cells. Protein capsids are unique to viruses and are not found in cells.
b) Nucleolus: The nucleolus is a structure found within the nucleus of eukaryotic cells. It is responsible for the production and assembly of ribosomal subunits. As such, it is a component of cells and is not exclusive to viruses.
c) Ribosomes: Ribosomes are cellular structures responsible for protein synthesis. They are found in all types of cells, both prokaryotic and eukaryotic. While viruses do not possess their own ribosomes, they rely on the host cell's ribosomes to replicate and produce viral proteins.
d) Cytosol: The cytosol refers to the liquid portion of the cytoplasm that surrounds the organelles within a cell. It contains various molecules, such as ions, sugars, and amino acids, necessary for cellular processes. Cytosol is a vital component of cells, but it is not specific to viruses.
In conclusion, the protein capsid is the correct answer, as it is unique to viruses and not found in cells.