How does/would “altered protein structure” affect physiological/biological processes?

Answer 1

It really depends on the protein and how its structure is altered. For instance, in cystic fibrosis there is a single amino acid substitution that doesn't actually impact the final structure of the protein, but it makes it fold slower. Because it fold too slowly, the cell thinks it is defective and destroys it.

If a membrane transporter that allows ions like sodium to cross the cell membrane were mutated and a hydrophobic amino acid was placed in the channel itself instead of the transmembrane domains, then sodium would be less likely to enter and pass through the channel.

But like I said, it really depends on the protein and the structural change you are talking about.