This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Physiology
Tyrosine kinase receptors: 
Select and explain. 
A. Have constitutively active tyrosine kinase domains, B. Phosphorylate and activate ras directly, C. Mediate cellular processes involved in growth and differentiation, D. Are not phosphorylated upon activation
C: Mediate cellular processes involved in growth and differentiation
Answer: C: Mediate cellular processes involved in growth and differentiation 
Explanation: Ans. C. Mediate cellular processes involved in growth and differentiationa. The activation of tyrosine kinase receptors often results in a cellular response that is involved in growth or differentiation. Tyrosine kinase receptors do not have constitutively active receptors; if this were true, there could be no regulation of signaling.b. The activation of ras occurs indirectly by the activation of adapter molecules (Grb2 and SOS) that associate with phosphorylated tyrosine residues in the cytoplasmic tail of the receptor. The activation of tyrosine kinase receptors usually involves multimerization into dimers or trimers.