fibrous and globular proteins

structure of fibrous protein

• little or no tertiary structure, made up of primary and secondary structures mainly

• made of long polypeptide chains with cross-linkages

• insoluble in water due to exposed hydrophobic groups

structure of globular proteins

• tertiary/3D (and quaternary) structure held by hydrogen/disulphide bonds

• folded into globular shape

• soluble in water because globular proteins folded in a way that hydrophillic groups are on the outside and hydrophobic groups are on the inside - exposed R groups are either polar or ionic which enables them to form hydrogen bonds with water which is a polar solvent

example of fibrous protein

collagen

example of globular protein

Haemoglobin

what is collagen made up of?

glycine and amino acids that have small R groups

why is the R groups in fibrous proteins small?

small R groups enables collagen fibres to be close together this allows formation of bonds that hold polypeptide chains together

why are fibrous proteins strong?

it’s made of three polypeptide chains held together by many hydrogen bonds

why are fibrous proteins flexible

Due to kinks in the protein chain

describe the structure of haemoglobin

For polypeptide chains (Two alpha and two beta) Each attached to iron heam prosthetic group