What do you notice about the ligands and their receptors in these images?

What can be noticed about the ligands and their receptor is that the configuration of both coincide, as a key would with its lock, which demonstrates the specificity of a receptor by its ligand.

Explanation:

A ligand corresponds to a molecule considered a signal or a messenger, while the receptor is a protein on the cell surface, with the capacity to accept a ligand.

Ligands and receptors constitute pairs that complement each other, so that each receptor can bind to a specific ligand, similar to what happens with a key and a lock.

Once the ligand-receptor complex is formed, changes occur inside the cell, which define a certain effect.

the answer would be b

explanation:

1 digestive system

2 stomach

3 bladder

4 carbon deoxide

5 tiger