Identify the amino acids in the tripeptide

The tripeptide is: $\text{Asp–Glu–Lys}$

where:

• Asp = aspartic acid
• Glu = glutamic acid
• Lys = lysine

Write the ionizable/functional side-chain groups

Each amino acid contributes the following side-chain functional groups:

• Aspartic acid (Asp): one extra carboxyl group in side chain $-CH_2-COOH$
• Glutamic acid (Glu): one extra carboxyl group in side chain $-CH_2-CH_2-COOH$
• Lysine (Lys): one extra amino group in side chain $-(CH_2)_4-NH_2$

Count terminal groups in the tripeptide

In a tripeptide, after peptide bond formation:

• one N-terminal amino group remains free
• one C-terminal carboxyl group remains free

So terminal groups are:

• $1$ free amino group
• $1$ free carboxyl group

Count all relevant groups

Total groups present:

• N-terminal amino group: $1$
• C-terminal carboxyl group: $1$
• Asp side-chain carboxyl group: $1$
• Glu side-chain carboxyl group: $1$
• Lys side-chain amino group: $1$

Hence, $1+1+1+1+1=5$

Final answer

The number of such groups present in the tripeptide Asp–Glu–Lys is: $\boxed{5}$

Comparison with stored answer

Stored correct answer = $5$

Our derived answer also = $5$. So they agree.