Question

suggest how a protein might have been hydrolyzed to give the amino acids. keep in mind that this is made from human consumption.

Answer 1

Hydrolysing proteins using hydrochloric acid

The chemistry of the reaction

If you have already studied the hydrolysis of amides under acidic conditions, you will find that this is basically the same reaction. That's not surprising because what biologists and biochemists call a peptide link (in proteins, for example) is what chemists call an amide link.

With an amide like ethanamide, the carbon-nitrogen bond in the amide group is broken and you get a carboxylic acid formed:

Now imagine doing the same thing with a simple dipeptide made of any two amino acids.

Instead of ammonium ions, you get positive ions made from the -NH₂ groups reacting with hydrogen ions.

You need the extra hydrogen ion in the equation (compared with the amide equation) to react with the -NH₂ group on the left-hand end of the dipeptide - the one not involved in the peptide link.

If you scale this up to a polypeptide (a protein chain), each of the peptide links will be broken in exactly the same way. That means that you will end up with a mixture of the amino acids that made up the protein - although in the form of their positive ions because of the presence of the hydrogen ions from the hydrochloric acid.