Proteins: Amino Acids and Peptide Bonds

This lesson covers the structure of amino acids, the formation of peptide bonds, and the assembly of polypeptides as required by the Edexcel A-Level Biology B specification (9BI0), Topic 1: Biological Molecules. You need to understand the general structure of amino acids, how they join together, and the significance of the R-group in determining the properties of different amino acids.

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Introduction to Proteins

Proteins are the most structurally and functionally diverse group of biological molecules. They are involved in virtually every biological process:

• Enzymes — biological catalysts (e.g. amylase, DNA polymerase)
• Structural proteins — collagen (tendons, skin), keratin (hair, nails), actin and myosin (muscle)
• Transport proteins — haemoglobin (oxygen transport), channel proteins (ion transport across membranes)
• Hormones — insulin, glucagon (blood glucose regulation)
• Antibodies — immunoglobulins (immune defence)
• Receptors — membrane proteins that bind signalling molecules
• Motor proteins — myosin (muscle contraction), kinesin (intracellular transport)

All proteins are polymers of amino acids. The sequence of amino acids in a protein is determined by the sequence of nucleotides in DNA (the genetic code).

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Amino Acid Structure