This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Structure & Function of Proteins), Subject name: Biochemistry
Role of Ubiquitin in cell - 
Select and explain. 
A. Energy dependent protein folding, B. Energy independent protein folding, C. Energy dependent protein degradation, D. Energy independent protein degradation
C: Energy dependent protein degradation
Answer: C: Energy dependent protein degradation 
Explanation: Ans. is 'c' i.e., Energy dependent protein degradation o There are two major enzyme systems responsible for degradation of damaged or unneeded proteins1) Ubiquitin-proteosome proteolytic pathway# Defective protein is first covalently attached to ubiquitin. Covalent bond is formed between glycine (a- carboxyl group) of ubiquitin and lysine (amino group) of target protein.# Ubiquitinated protein is then degraded in proteosomes by ATP dependent (energy dependent) mechanism.2) Lysomes# Proteins are degraded by proteolytic enzymes which is energy independent (non-energy dependent).