This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Ubiquitin is called so as: 
Select and explain. 
A. Present in all eukaryotic cells, B. Takes pa in impoant reactions, C. Is highly conserved, D. None of the above
A: Present in all eukaryotic cells
Answer: A: Present in all eukaryotic cells 
Explanation: Ubiquitin, so named because it is present in all eukaryotic cells, is a small (8.5 kDa, 76 residues) polypeptide that targets many intracellular proteins for degradation. The primary structure of ubiquitin is highly conserved. Ref: Harper 28th edition, chapter 28.