Proteins Flashcards
What are the various classes of natural occurring amino acids? (7)
Aliphatic Aromatic Sulfur containing Basic Acidic Uncharged polar Other: proline - neither cyclic or aromatic so sits on its own
Define Aliphatic.
relating to or denoting organic compounds in which carbon atoms form open chains (as in the alkanes), not aromatic rings.
Define Aromatic.
relating to or denoting organic compounds containing a planar unsaturated ring of atoms which is stabilized by an interaction of the bonds forming the ring, e.g. benzene and its derivatives.
What are the 9 functions of proteins?
- Proteins have a huge range of function in the body:
1) Movement
2) Protection
3) Transport
4) Enzymes
5) Receptors
6) Structural
7) Storage
8) Hormones
9) Control of gene expression
Define the term primary structure of a protein.
-Primary structure: The sequence of amino acids in a polypeptide chain (with peptide bonds). -> 20 possible occupants with enormous range of sequences theoretically possible, this is a source of versatility in protein structure and function.
Define the term secondary structure of a protein.
The spatial arrangement of amino acids residues that are near each other in the linear sequence. Either in the form of an alpha helix or Beta pleated sheet.
What is an alpha helix? (with example)
An alpha helix is in a telephone cord shape held in place by hydrogen bonds between every N-H group and the oxygen of the C=O group in the next turn of the helix. – troponin (measured in blood to check for MI)
What is a Beta pleated sheet?(with example)
Beta pleated sheet structure is helix together by hydrogen bonds between the amino groups of linear polypeptide chains – fatty acids and porin.
Define the tertiary structure of a protein.
The spatial arrangement of amino acid residues that are far apart in a linear sequence. They are held together by: Van der waals bonds, Ionic interactions, hyrdrogen bonds, disulphide bridges and hydrophobic interactions.
What is a Van der Waals bond?
Van der Waals – non-specific, weak attractions between atoms 0.3-0.4 nm apart – these are individually weak (but large number of them) but in a folded protein structure a large number exist – thereby stabilizing the structure.
What are ionic interactions?
-Ionic interactions – occur between 2 close, op charged R groups. – strong but few in most proteins
What are hydrogen bonds?
Hydrogen bonds – similar to van der waals but stronger and permanent (1/20 strength of a covalent bond though) occur when H is bonded to either O, N, or F and a lone pair of electrons are present.
What are Disulphide bridges?
Disulphide bridges – strong covalent bonds between two cysteine residues, occur between as well as within polypeptides.
What are hydrophobic interactions?
Hydrophobic interactions –these are intra-polypeptide interactions which occur in an environment within proteins from which water is excluded.
Define the Quaternary structure of a protein.
- Quaternary: Refers to the spatial arrangement of individual polypeptide chains in a multi-subunit protein – Haem and CRP (measured in blood to see if infections responding to course of antibiotics)
