Protein Structure Flashcards
What is the primary structure of a protein?
The primary structure is the order in whicht the amino acids have been synthesised together into the polypeptide. It determines all the higher levels of the proteins structure.
What is the secondary structure of a protein and what are the three main types?
This is stabalised by hydrogen bonding along the backbone of the polypeptide strand and the three main types are:
1) a-helix: A spiral shape with the R groups sticking outwards.
2) B-sheet: Parts of the chain run alongside eachother forming a crinkly sheet with the R groups sticking above and below. They are usually anti-parallel but can sometimes be parallel depending on the N and C termini.
3) Turns: This is where the chain folds back on itself.
Describe tertiary structure.
This is the final folded shape of the polypeptide and is produced by interactions of the R groups. They can be hydrophobic interactions (hydrophobic R groups are repelled by water and pushed to the inside of the protein), ionic bonds (between COO- and NH3+), van der waals interactions (LDF, permanent dipole to dipole, hydrogen bonding), or disulphide bridges (covalent bonds between sulfur containing R groups in the amino acid cysteine).
What are prosthetic groups?
Prosthetic groups are non-protein groups which are strongly bound to some proteins to give them added functions (e.g. haem groups in haemoglobin).
What is quaternary structure?
Most proteins which have several connected polypeptide subunits have quaternary structure. Proteins with a quaternary structure can show cooperativity between their polypeptides because changes to the shape of one subunit can affect the properties of the other subunits.
