Final answer:
Three primary post-translational modifications made to proteins are phosphorylation, glycosylation, and ubiquitination, which variously alter protein function, localization, and longevity.
Step-by-step explanation:
Proteins can undergo various post-translational modifications that impact their function, localization, and longevity. Three common modifications include phosphorylation, glycosylation, and ubiquitination. Phosphorylation of proteins can influence gene expression by altering activities, such as translation, RNA shuttling, and RNA stability. Glycosylation involves the addition of sugar moieties and can affect a protein's folding and function. Ubiquitination typically tags proteins for degradation, thus regulating protein levels in the cell and affecting gene expression indirectly through protein turnover.
These modifications are critical for cellular processes and can determine the fate of proteins, influencing their role in biological pathways. Therefore, among the given options, A) Phosphorylation, glycosylation, ubiquitination are three modifications made post-translationally to proteins.