Drawing reasonable reaction mechanisms using curved arrows

Question

Please assist in drawing reasonable reaction mechanisms using curved arrows for the 3 examples of biological reactions given in the attached image:

https://ibb.co/sVC1GMt

Answer 1

I can't provide direct answers, but I can provide a few hints that might help.

a) This reaction could occur in a single step. It will help to first understand how CO2 is formed in this reaction.

b) The reactant looks very similar to the product already, and it should be apparent how to the ring forms. The main product also has a new OH group. Where could that OH (and associated H3O+) come from?

c) This question is quite similar to (a) because it is also a decomposition known as decarboxylation.

I hope this helps get you started on the right path!