The Structure of Proteins

Functions of Proteins Fibrous proteins – structural, e.g. collagen. Globular proteins – metabolic functions, e.g. haemoglobin. It is their structure that allows them to carry out their functions.

Structure of Proteins Monomer units of proteins are called amino acids.

Structure of Proteins Amino Acids C

Structure of Proteins Amino Acids C N H H H H AMINO GROUP

Structure of Proteins Amino Acids C N H H H H AMINO GROUP O O O O C H H CARBOXYLGROUP

Structure of Proteins Amino Acids C N H H H H AMINO GROUP O O O O C H H CARBOXYL GROUP

Structure of Proteins Amino Acids C N H H H H AMINO GROUP O O O O C H H CARBOXYL GROUP H H

Structure of Proteins Amino Acids C N H H H H AMINO GROUP O O O O C H H CARBOXYL GROUP H H

Structure of Proteins Amino Acids C N H H H H AMINO GROUP O O O O C H H CARBOXYL GROUP H H R-GROUP (Variant)

Structure of Proteins Amino Acids C N H H H H AMINO GROUP O O O O C H H CARBOXYL GROUP H H R-GROUP (Variant)

Structure of Proteins PRIMARY STRCUTURE – Polypeptides Polypeptides are composed of amino acids bonded to each other, like beads on a string The bond that holds them together is called a peptide bond They are formed by loss of water so is called a condensation reaction.

Structure of Proteins PRIMARY STRCUTURE – Polypeptides

Structure of Proteins PRIMARY STRCUTURE – Polypeptides -OH from carboxyl group -H from amino group Forms peptide bond

Structure of Proteins Secondary Structure – α helix +ve -ve

Structure of Proteins Tertiary Structure – α helix 3D structure is formed by further bonds, depending on the function Disulphide bonds – strong and not easily broken down Ionic bonds – easily broken down by changes in pH (carobxy/amino groups) Hydrogen bonds – numerous be very easily broken down

Functions of Proteins Fibrous proteins – structural, e.g. collagen. Globular proteins – metabolic functions, e.g. haemoglobin. It is their structure that allows them to carry out their functions. i.e. the 3D structure is v.v.v important in carrying out it’s function Makes proteins distinctive – interacting with other molecules

Structure of Proteins Quaternary Structure Complex molecules containing many polypeptide chains

Structure of Proteins Example – haemoglobin:

Test for proteins