This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Translation, Subject name: Biochemistry
Which of the following post translational modification process is Irreversible ? 
Select and explain. 
A. Acylation, B. Phosphorylation, C. Ubiquitination, D. ADP ribosylation
C: Ubiquitination
Answer: C: Ubiquitination 
Explanation: Post translational modifications REVERSIBLE IRREVERSIBLE Disulfide bridge Proteolysis Glycosylation Ubiquitination Phosphorylation Lysine hydroxylation Acylation Proline hydroxylation N-acetylation Methylation ADP-ribosylation