It folds into a complex 3Dshape to be classified as a protein molecule
Name the 4 levels of protein structure
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
Describe the primary structure
The specificsequence of aminoacids in a polypeptidechain joined by peptidebonds
Describe the secondary structure
The oxygen atoms in the C--O groups have a small negative charge and the hydrogen atoms in the N-H groups have a small positive charge. The opposite charges attract and hydrogenbonds form. The hydrogen bonds cause the polypeptide chain to fold into alphahelixes or betapleatedsheets
Describe tertiary structure
The overall3Dshape of a polypeptide chain
Describe quaternary structure
Some proteins consist of multiple polypeptide chains working together as a large molecule (subunits). Quaternary structure shows how the individual subunits are arranged to form a 3D structure. Some proteins are also made up of non-protein molecules (prosthetic groups). Quaternary structure shows the position of prosthetic groups.
What are proteins with prosthetic groups called
Conjugated proteins
Name the 4 bonds that can form between the R groups
Hydrogen bonding
Ionic bonds
Disulfidebridges
Describe hydrogen bonding
A hydrogen bond forms when there are weak positive and negative bonds between the R groups. Hydrogen bonds are weak- they can be broken by high temperatures or changesinpH
Describe hydrophobic and hydrophilic interactions
Amino acids with hydrophobic R groups tend to clustertogether and are usually found in the centre of proteins to avoid water. Amino acids with hydrophilic R groups are usually found at the surface of proteins to interact with water molecules
Describe ionic bonds
Forms between aminoacids with charged R groups. The opposite charges attract to make an ionic bond. Ionic bonds are broken by changes in pH
Describe disulfide bonds
Happens when the Rgroup in the amino acids contain a sulfur atom. The two sulfur atoms form a covalent bond. Disulfide bonds are relativelystrong- they aren't broken by changes in pH or high temperature