Proteins

1
Proteins

• The work-horse of the cell

2
Figure 6.14 The induced fit between an enzyme
and its substrate
3
Figure 6.15 The catalytic cycle of an enzyme
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Table 5.1 An Overview of Protein Functions
5
Protein Structure

• Hierarchical levels of organization
• Primary
• based upon amino acid sequence
• Secondary
• based upon formation of hydrogen bonds between
  the amin and carboxyl groups along the peptide
  backbone
• Tertiary
• based upon interactions of side chains
• Quaternary
• based upon interactions between multiple
  subunits.

6
Amino Acids

• What are examples of amino acids?
• What do these have in common?
• How do they differ?

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Figure 5.15 The 20 amino acids of proteins
nonpolar
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Figure 5.15 The 20 amino acids of proteins
polar and electrically charged
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Figure 5.16 Making a polypeptide chain
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Figure 5.19 A single amino acid substitution in
a protein causes sickle-cell disease
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Protein Structure

• Hierarchical levels of organization
• Primary
• based upon amino acid sequence
• Secondary
• based upon formation of hydrogen bonds between
  the amin and carboxyl groups along the peptide
  backbone
• Tertiary
• based upon interactions of side chains
• Quaternary
• based upon interactions between multiple
  subunits.

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Figure 5.20 The secondary structure of a protein
13
Protein Structure

• Hierarchical levels of organization
• Primary
• based upon amino acid sequence
• Secondary
• based upon formation of hydrogen bonds between
  the amin and carboxyl groups along the peptide
  backbone
• Tertiary
• based upon interactions of side chains
• Quaternary
• based upon interactions between multiple
  subunits.

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Figure 5.22 Examples of interactions
contributing to the tertiary structure of a
protein
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Figure 5.17 Conformation of a protein, the
enzyme lysozyme
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Protein Structure

• Hierarchical levels of organization
• Primary
• based upon amino acid sequence
• Secondary
• based upon formation of hydrogen bonds between
  the amin and carboxyl groups along the peptide
  backbone
• Tertiary
• based upon interactions of side chains
• Quaternary
• based upon interactions between multiple
  subunits.

17
Figure 5.23 The quaternary structure of proteins
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Figure 5.24 Review the four levels of protein
structure
19
Why would a change in pH have a deleterious
effect on the function of a protein?