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: Physiology
True regarding Na+ – K+ pump 
Select and explain. 
A. Hetrodimer – homogenous, B. Hetrodimer – heterogenous, C. Homodimer – heterogenous, D. Homodimer – homogenous
B: Hetrodimer – heterogenous
Answer: B: Hetrodimer – heterogenous 
Explanation: Structure of Na+K+ pump
2 subunits- α subunit is larger and β subunit is smaller. 
Hence it is Heterodimer.
α subunits- α1, α2 & α3 isoforms.
β subunits- β1, β2 & β3 isoforms. Hence it is heterogeneous.