1.4.4

Tertiary & Quaternary Protein Structure

Test yourself on Tertiary & Quaternary Protein Structure

Test your knowledge with free interactive questions on Seneca — used by over 10 million students.

Tertiary Structure of Proteins

The secondary polypeptide folds further to form a tertiary, three-dimensional polypeptide chain.

R groups

R groups

  • R groups are the side chains on amino acids.
  • Interactions between R groups creates the complex 3D tertiary structure of a protein.
  • The 3D structure is usually coiled or folded.
Holding the 3D structure

Holding the 3D structure

  • There are many weak and strong interactions that determine the final 3D shape of the protein (e.g. ionic bonds, hydrogen bonds and disulphide bridges).
  • When the protein loses its 3D shape, it may no longer be functional.
Ionic bonds

Ionic bonds

  • Charged amino acids have a positively or negatively charged ion in their side chain.
    • Charged amino acids can form relatively strong ionic bonds with other charged amino acids.
  • Ionic bonds between amino acids are quite rare.
Disulfide bridges

Disulfide bridges

  • Disulfide bridges are also known as S-S bonds or disulfide bonds.
    • These are covalent bonds set up within proteins containing cysteine (CYS) amino acids.
Hydrogen bonds

Hydrogen bonds

  • Hydrogen bonds also form between amino acids.
  • Hydrogen bonds are relatively weak but when there are many, the overall stability of the tertiary structure increases.

Quaternary Structure of Proteins

Multiple 3D polypeptides can come together to form a complex, quaternary structure. Examples of proteins with a quaternary structure are:

Insulin

Insulin

  • Weak interactions between the subunits in the insulin polypeptide help to stabilise the overall quaternary structure.
    • Insulin has a combination of hydrogen bonds and disulfide bridges that cause it to form a clumped, globular (ball) shape.
Haemoglobin

Haemoglobin

  • Haemoglobin contains four polypeptides (subunits) surrounding a central haem group.
Collagen

Collagen

  • Collagen is a fibrous protein found in skin.
Jump to other topics
1

Biological Molecules

2

Cells

3

Substance Exchange

4

Genetic Information & Variation

5

Energy Transfers (A2 only)

6

Responding to Change (A2 only)

7

Genetics & Ecosystems (A2 only)

8

The Control of Gene Expression (A2 only)

9

Mathematical Skills

Practice questions on Tertiary & Quaternary Protein Structure

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
  2. 2
  3. 3
Answer all questions on Tertiary & Quaternary Protein Structure

Unlock your full potential with Seneca Premium

  • Unlimited access to 10,000+ open-ended exam questions

  • Mini-mock exams based on your study history

  • Unlock 800+ premium courses & e-books

Get started with Seneca Premium