g3. Quaternary structure (proteins)

uh huh

What is a quaternary structure made up of?

two or more polypeptide chains

What will happen if two or more peptide chains associate with non-protein groups?

they will form large, complex molecules like haemoglobin

What can quaternary structures be classified as?

Globular or fibrous

What functions do fibrous proteins have?

Structural

What is the structure of a fibrous protein?

parallel chains or sheets with many cross-linkages to form long fibres

Features of a fibrous protein

insoluble in water, strong and tough

Examples of fibrous proteins

Keratin and collagen

Where is collagen, a fibrous protein, found and what is the structure of it?

• found in tendons as it provides strength and toughness

• 3 identical polypeptides are twisted together like a rope linked by hydrogen bonds, making it very stable

What functions do globular proteins have?

metabolic functions

What is the structure of a globular protein?

folded into 3D spherical molecules and are compact

Feature of a globular protein

soluble in water and compact

Examples of globular proteins

enzymes, hormones, antibodies, Haemoglobin

What is haemoglobin and what type of protein is it?

• It’s an oxygen-carrying pigment found in red blood cells.

• It’s a conjugated protein - it has a prosthetic (non-protein) part

What is haemoglobin made up of?

4 polypeptides (2 alpha chains and 2 beta chains), and 4 haem groups (non-protein)