a. i. Draw the structure, showing all bonds, of the amino acid serine as it would exist in solution at pH 2. ii. Name the functional group on the side chain of serine. b. Write the molecular formula of the amino acid phenylalanine. c. Two different dipeptides can form between phenylalanine and serine. i. Draw the structure of one of these dipeptides. ii. Circle the peptide (amide) functional group in the dipeptide you have drawn in part i. above. d. In the space below, sketch a covalent link that can form between the side chains of two cysteine residues. Only the relevant atoms that form the link need to be shown.

SSCE VCE Chemistry Structure, Nomenclature, and Properties of Organic Compounds: a. i. Draw the structure, showin

a. i - VCE - SSCE Chemistry - Question 5 - 2008 - Paper 1

Question 5

a. i. Draw the structure, showing all bonds, of the amino acid serine as it would exist in solution at pH 2. ii. Name the functional group on the side chain of seri... show full transcript

Worked Solution & Example Answer:a. i - VCE - SSCE Chemistry - Question 5 - 2008 - Paper 1

Step 1

Draw the structure, showing all bonds, of the amino acid serine as it would exist in solution at pH 2.

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Answer

The structure of serine at pH 2 includes a central carbon (C) atom bonded to an amino group (NH3 extsuperscript{+}), a carboxyl group (COOH), a hydrogen atom (H), and a hydroxymethyl side chain (CH2OH). The structure can be drawn as:

     H    
     |    
H2N - C - COOH  
     |    
   CH2OH

Step 2

Name the functional group on the side chain of serine.

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Answer

The functional group on the side chain of serine is a hydroxyl group (-OH).

Step 3

Write the molecular formula of the amino acid phenylalanine.

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Answer

The molecular formula of phenylalanine is C9H11NO2.

Step 4

Draw the structure of one of these dipeptides.

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Answer

One dipeptide formed from serine and phenylalanine can be represented as follows:

     H    
     |    
H2N - C - COOH 
     |   | 
   CH2OH  C - COOH
           | 
           H 
       Ph (phenyl group)

Step 5

Circle the peptide (amide) functional group in the dipeptide you have drawn in part i. above.

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Answer

The peptide (amide) functional group can be circled in the dipeptide structure:

     H    
     |    
H2N - C - COOH 
     |   | 
   CH2OH  C - COOH
           | 
           H 
       Ph (phenyl group)

Here, the bond between the carbon of the -COOH group and the nitrogen of the -NH2 group forms the peptide bond.

Step 6

In the space below, sketch a covalent link that can form between the side chains of two cysteine residues.

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Answer

The covalent link formed between the side chains of two cysteine residues is a disulfide bond (S-S). It can be represented as:

   HS-CH2-CH(NH2)-COOH  +  HS-CH2-CH(NH2)-COOH  
         |                          | 
          S - S

a. i - VCE - SSCE Chemistry - Question 5 - 2008 - Paper 1

Worked Solution & Example Answer:a. i - VCE - SSCE Chemistry - Question 5 - 2008 - Paper 1

Draw the structure, showing all bonds, of the amino acid serine as it would exist in solution at pH 2.

Name the functional group on the side chain of serine.

Write the molecular formula of the amino acid phenylalanine.

Draw the structure of one of these dipeptides.

Circle the peptide (amide) functional group in the dipeptide you have drawn in part i. above.

In the space below, sketch a covalent link that can form between the side chains of two cysteine residues.

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