Proteins Flashcards
What are the five roles PROTEIN play?
Structural support (Keratin and collagen)
Immune protection (antibodies)
Catalyst (enzymes)
Chemical communication (hormones)
Transport (haemoglobin and membrane carrier proteins)
What is the structure of a protein?
A central carbon with an amino group (NH2) on one side, and a carboxylic acid on the other (COOH). The composition of a side chain (R) determines the name and properties of each amino acid.
How do aminos bind?
Peptide bonds form as the result of condensation reactions. An -OH from the carboxylic group and a -H from the amino group are removed as H20. A peptide bond is formed between the Carbon and Nitrogen. First a dipeptide and eventually a polypeptide.
What are the four structures of proteins?
Primary, Secondary, Tertiary and Quarternary.
Describe PRIMARY structure
The PRECISE sequence of amino acids in a polypeptide chain. Only TWENTY amino acids, their TYPE and ORDER which they bond together determines their primary structure, and the SHAPE and PROPERTIES of a protein.
Describe SECONDARY structure
Hydrogen bonds form between amino acids and they COIL into ALPHA HELIX or FOLD into BETA PLEATED SHEETS, where a hydrogen bond forms between oxygen and hydrogen to create support.
Polypeptide bonds can turn sharply in any direction.
Describe TERTIARY structure
FINAL 3D structure of a SINGLE polypeptide chain. Coil and fold further. NO symmetry.
- DISULPHIDE COVALENT BONDS: Two CYSTEINE amino acids from a strong double bond (S=S) between the two SULPHUR atoms within the cysteine monomers.
- IONIC BONDS: Oppositely charged R-Groups nearby form an ionic bond.
- Hydrogen bonds: Typical.
- Hydrophobic and hydrophilic interactions: a GLOBULAR protein will orientate itself as such so that the hydrophobic part is towards the CENTRE and the hydrophilic towards its EDGES.
ENZYMES is a good example of a FUNCTIONAL protein in the TERTIARY conformation.
Describe QUARTENARY structure
Made of more than one polypeptide chain. Haemoglobin is made of an alpha and beta chain, thus is a dimmer. Final 3D structure for proteins with more than one chain.
What is denaturing?
When the structure and shape of a protein is changed (could be by chemical, temperature etc) it is no longer able to carry out its function, underlying that shape and structure is instrumental to the protein carrying out its biological function. eg. Active site of enzyme.
Function of protein as biochemical reaction
Enzymes speed up reactions by lowering the activation energy. They are biological catalysts. They can speed up the uptake of oxygen and the digestion of food. Reactions may still take place without them, but very slowly, and may not support human life.
Function of protein as physical structure
Major factor in the production of hair, fingernails and collagen. Also support structure for tissue type such as muscle.
Function of protein as immunology
Immune system produces antibodies to match pathogens. When antibodies attached to pathogens, it signals to the immune system knows to set about the destruction of them.
Function of protein as receptor proteins
Found within membrane of cells or nuclear envelope, these proteins receive chemical messages to signal changes within the cell or nucleus.
Function of protein as membrane transport
Located in the membrane:
Channels diffuse ions down their gradient, in and out of cells
Carrier Proteins form conveyors to move ions against their concentration gradient.
Function of protein as MOVEMENT
Proteins such as ACTIN and MYOSIN can form fibers that shorten or lengthen based on stimulation. The fibers are the foundation of muscles. Without these protein structures, movement of organisms larger than a few cells would be impossible.
