Proteins serve a variety of purposes, and give living cells their diverse forms and functions. Some proteins have a structural function; such proteins make up cartilage, hair and nails, for example. A special class of proteins, called enzymes catalyze important chemical reactions for the cell that could not normally occur in their absence. Some proteins serve as membrane channels which facilitate the passage of molecular particles into and out of the cell. Some hormones, like insulin, are proteins, and serve to regulate body functions (insulin controls blood-sugar levels). Proteins are also needed for muscle contraction and to aid in the defence of body cells against foreign invaders. The above are only a few of the many diverse functions of proteins.
In either case, the result of viral infection is that the virus' genetic material gets into the cell cytoplasm, which contains all the necessary enzymes and other materials that are needed for the replication of the virus' genetic material and the synthesis of its proteins.
Genetic Control of Protein Synthesis, Cell Function, ..
Living organisms synthesize almost all proteins using only twenty different amino acids. Polypeptides form a unique three-dimensional structure based on the type and position (sequence) of these amino acids. Within the sequence, amino acid R-groups form chemical interactions that create a specific three-dimensional structure. These R-groups are commonly called “side chains” because they are not involved in the peptide bonds. The R-groups stick out on the side of a polypeptide, freeing them to chemically interact with one another. Side chain interactions form each protein’s specific structure, a structure uniquely capable of performing that protein’s cellular function.