5. Proteins - Protein Structure Flashcards
Name the 4 levels of protein structure.
Primary.
Secondary.
Tertiary.
Quaternary.
What is a primary structure?
The sequence of amino acids in the polypeptide chain.
What is a secondary structure?
Polypeptide chain doesn’t remain flat and straight.
Hydrogen bonds form between the amino acids in the chain.
Automatically coil into an alpha helix or beta pleated sheet.
What is a tertiary structure?
The coiled or folded chain of amino acids is often coiled.
More bonds form between different parts of the polypeptide chain including hydrogen bonds, ionic bonds and disulfide bridges.
In a tertiary structure when do disulfide bridges form?
Whenever 2 molecules of the amino acid cysteine come close together.
One sulfur atom in one cysteine to the sulfur atom in the other.
What is a Quaternary structure?
When proteins are made of several different polypeptide chains held together by bonds.
For proteins made from more than one polypeptide chain, the proteins final 3D structure.
Amino acid structure
R group - this varies
Carboxyl group - COOH
Amino group - H2N
And H
Why is primary structure important
It determines the second / tertiary / quaternary structure later on
What do major structures does the secondary structure form ?
Alpha helices
Beta pleats
Bond in secondary
Hydrogen bonds
These are weak
Tertiary bonds
Hydrogen
Ionic
Covalent - strong
Disulfide bridges with sulphur atoms
Prosthetic groups
Any non- polypeptide incorporated into structure
Like haemoglobin
