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
Salvage pathway of purine nucleotide synthesis are used by all except ? 
Select and explain. 
A. Brain, B. Liver, C. RBC, D. Leukocytes
B: Liver
Answer: B: Liver 
Explanation: Purine nucleotide synthesis occurs by two pathways :- 1.De novo synthesis 2.Salvage pathway Liver is the major site of purine nucleotide biosynthesis (de novo). Ceain tissues cannot synthesize purine nucleotides by de novo patyway, e g. brain, erythrocytes and polymorphonuclear leukocytes. These are dependent on salvage pathway for synthesis of purine nucleotides by using exogenous purines, which are formed by degradation of purine nucleotides synthesized in liver.