Final answer:
Ion channel selectivity is largely determined by factors such as size exclusion and electrochemical exclusion, where size exclusion relates to the diameter of ions and electrochemical exclusion to the charge specificity of the ion channel.
Step-by-step explanation:
The selectivity of an ion channel in transport is determined by several factors, including the diameter of the pore, the charge of the amino acids within the channel, and the interaction between ions and water molecules. Ion channels can be specific for the diameter of the ion they transport, which is related to the distance between amino acids in the channel. This aspect is known as size exclusion. Moreover, the selectivity can also be influenced by electrochemical exclusion, where the channel pore is charge-specific, with channels for cations having negatively charged side chains and anions channels having positively charged side chains.