1/2) Protein supplies between 0 and 10% of your energy demands. At rest it is close to 0%, during times of extreme stress and starvation close to 10%.
Your body will deaminate certain amino acids to produce glutamine with the remaining carbon skeleton being metabolized as fat (acetyl coA). The glutamine / glutamic acid can enter krebs like a carb.
3) Amino acids are used to form all sorts of products and some of these are lost at greater rates following exercise. However, your kidneys are always working at retaining as much as possible.
4)Yes damage does occur and proteins are always being created and destroyed. Your body will not work at retaining a protein it doesn't need. However, exercise does not effect muscle protein turnover as much as many would imagine.
Protein and amino acid metabolism in human muscle.
http://www.ncbi.nlm.nih.gov/pubmed/9...ubmed_RVDocSum
5)Your body has a large protein / amino acid pool that it is constantly being drawn from and fed at the same time.
