the structure of proteins. functions of proteins fibrous proteins – structural, e.g. collagen....

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 ProteinsAmino Acids

C

Structure of ProteinsAmino Acids

C

Structure of ProteinsAmino Acids

CNH

H

AMINO GROUP

C

Structure of ProteinsAmino Acids

CNH

H

AMINO GROUP

C

Structure of ProteinsAmino Acids

CNH

H

AMINO GROUP

O

OC

H

CARBOXYL GROUP

H

Structure of ProteinsAmino Acids

CNH

H

AMINO GROUP

O

OC

H

CARBOXYL GROUP

H

Structure of ProteinsAmino Acids

CNH

H

AMINO GROUP

O

OC

H

CARBOXYL GROUP

H

R-GROUP (Variant)

Structure of ProteinsAmino Acids

CNH

H

AMINO GROUP

O

OC

H

CARBOXYL GROUP

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 ProteinsExample – haemoglobin:

Test for proteins