Levels of protein structure as ocr

Primary structure:

• The sequence of amino acids in the polypeptide chain
• Held together by peptide bonds between the amino acids

Secondary structure: The folding of the polypeptide:

• Either alpha helix or Beta pleated sheets
• Theyre both stabilized by Hydrogen bonds.

Tertiary structure: 3D structure

• Different parts of the ribbon like structure has different bonds holding it in place.
• Hydrogen bonds anywhere that has polar groups
• Disulfide bridges between the sulfur containing R groups
• Ionic bonds between R groupds
• Hydrophobic and hydrophilic interactions between non polar R groups.

Some of these bonds break when the proteins are heated up or treated with acids and alkalis. This changes the tertiary structure and the proteins dont function anymore and become denatured

Quaternary: the final 3D structure of a protein

Haemoglobin; has quaternary structure

This is because its made up of more than 2 polypeptide bonds, it has 4 bonds in total. They are held together by ionic and hydrogen interactions between R groups on adjacent polypeptides.

Cartillage is a fibrous protein:

• three alpha helixes wound tightly together, held together by covalent bonds
• can be found in skin, hair, bones etc
• the sequence of the polypeptides is staggered so glycine can be found at every position along the triple helix
• This means that it can pack more closely together and from hydrogen bonds along the whole length of the chain