Amino acids contain which of the following functional groups?

Assume that a particular amino acid has an isoelectric point of $6.0$. In a solution at $pH$ $1.0$,which of the following species will predominate?

The acid showing salt-like character in aqueous solution is

$1.$ Glycylglycine
$2.$ Alanylalanine
$3.$ Glycylalanine
$4.$ Alanylglycine
The dipeptides which may be obtained from the amino acids glycine and alanine are

Amino acids are

The number of possible tripeptides formed involving alanine $(ala)$,glycine $(gly)$,and valine $(val)$,where no amino acid has been used more than once is: