Amino Acids

H                       R                       O

         N              C           C

H                       H                      OH

H                         R1                         O      H                        R2                            O

           N              C             C                                N             C                C

H                         H                           OH   H                          H                              OH

                           Condensation                          -H2O

     H                       R1                 O                  H                     R2                       O

               N             C                   C                  N                     C             C     

    H                        H                                                              H                         OH

• Membrane carriers and pores e.g. active transport, facilitated diffusion
• Many hormones are proteins
• Provid building materials important for growth and repair
• Crucial to most metabolic activity
• Antibodies are proteins
• Enzymes are proteins
• Structural Components e.g. muscle and bone

• R-groups sometimes carry a charge, either +ve or -ve
• Where oppositely charged amino acids are found close together / to each other an ionic bond forms
• Ionic bond between ionised r-groups

              R    -------- R     

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• The amino acid cysteine contains sulfure
• Where two cysteines are found close to each other a covalent bond can form
• Disulphide bond between R-groups containing -SH groups

                   S              S

• As in secondary structure
• Wherever slightly positively charged groups are found close to slightly negatively charged groups hydrogen bonds form.
• Hydrogen bond

       N            H ---------O = C

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• In water based environment hydrophobic amino acids will be most stable if they are held together with water excluded
• Hydrophilic amino acids tend to be found on the outside in globular proteins, with hydrophobic amino acids in the centre