Question

What is the net charge on the amino acid glycine at pH 7? at pH 12?

Answer 1

Step-by-step explanation:

The chemical formula for the amino acid glycine is;

`\bold{HOOC—CH_2—NH_2}`

• In solution, the acidic part of the molecule that is
  `\bold{COOH}` donates a proton
  `{H}^(+)` which is accepted by the basic side of the molecule which is
  `\bold{NH_2}`.
• The molecule in solution becomes:

`\bold{ ^ - OOC—CH_2—{NH_3}^(+)}`

• In this state both negative and positive charges cancel out and the net charge on the molecule becomes zero.

• At a pH of 7 ( neutral state), both negative and positive charges cancel out on each each and the net charge becomes zero

`\bold{ ^ - OOC—CH_2—{NH_3}^(+)}`

• At a pH of 12( basic state), there are more
  `\bold{{OH}^(-)}` ions present than
  `{H}^(+)` ions, the
  `\bold{{OH}^(-)}` ions draws a proton from
  `{NH_3}^(+)` making it neutral leaving the other part of the molecule negatively charged that's
  `\bold{{COO}^(-)}`. Thus the net charge on the molecule becomes negative ( -1).

`^-OOC—CH_2—{NH_3}^(+) + {OH}^(-) \: \rightarrow ^ - OOC—CH_2—{NH_2} \: + H_2O \\`