What is the difference between type a and type b blood?

It is very easy and simple difference that is antigens and antibodies .
it can be different due to donor and recipient also .
A type blood having antigens
whereas B type blood having nil.

B type blood having antibodies
whereas A type blood having nil.

If you want the answer you need to post the figure above that it's talking about and you

Six amino acids have side chains that are polar but not charged. these are serine (ser), threonine (thr), cysteine (cys), asparagine (asn), glutamine (gln), and tyrosine (tyr). these amino acids are usually found at the surface of proteins, as discussed in the proteins 2 module.