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. 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 Families 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 an amino group, a carboxyl group, and a hydroxymethyl side chain. The amino group is protonated, giving it a positive charge, while the carboxyl group is deprotonated, maintaining a neutral charge. The complete structure is:

       H
       |
   H2N-C-COOH
       |  
       CH2
       |  
       OH

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 possible dipeptide formed from phenylalanine and serine is phenylalanine-serine. The structure would look like:

   H   O   H
   |   ||  |
H2N-C--C-N-C-COOH
   |     |  |
   CH2  CH  OH

Step 5

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

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Answer

In the dipeptide structure drawn, the peptide bond (amide functional group) is between the carbon of the carboxyl group of serine and the nitrogen of the amino group of phenylalanine. It can be highlighted as:

   H   O   H
   |  ( ) |
H2N-C--C-N-C-COOH
   |     |  |
   CH2  CH  OH

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 bond between the side chains of two cysteine residues forms a disulfide bond (–S–S–) when the sulfhydryl groups (-SH) of each cysteine oxidize. The structure of this bond can be represented simplistically as:

    R1-SH
       | 
       S-S
       | 
    R2-SH

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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