Proteins

Almost every structure in an organism and all enzymes are composed of protein. Although not a very good fuel (4 kcal/gram), proteins are crucial to life. You can find them in meat, poultry, nuts, fish, etc.

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Proteins are polymers of amino acids. Every amino acid has a amine group, a carboxyl group, and a R (variable) group. Amino acids are connected to form proteins by peptide bonds. These bonds are formed through dehydration synthesis.

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There are four types of protein structure:

• The primary structure of protein is a long polypeptide chain of amino acids.
  
  
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• The secondary structure of protein is an alpha helix or a beta sheet. The twisting of the polypeptide chain occurs because of hydrogen bonding between the amino groups and the acid groups.
  
  
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• The tertiary structure of protein is globular. Interactions with water and disulfide bridges alter the shape of the protein.
  
  
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• The quaternary structure of a protein involves more than one polypeptide chain. All the interactions in the primary, secondary, and tertiary structures are also occurring.
  
  
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