Physiology: Biological Chemistry: Proteins, Enzymes and pH

Living things contain instructions for constructing and reproducing themselves, in the form of DNA, deoxyribonucleic acid.

DNA contains the instructions for making all the proteins that a living thing contains.

Only the instructions for one protein can be used at a time. So the section of DNA encoding the protein needed is transcribed into mRNA: this has complementary bases to the original DNA, and uses the base Uracil instead of Thymine.

Each mRNA base (codon) encodes an amino acid. tRNA molecules with anticodons complementary to the mRNA bring the correct amino acids to join into a polypeptide chain. This occurs in the ribosomes of the cell.

There are 20 amino acids, which have the same basic structure, but different side-chains with different properties. 

The primary structure of a protein refers to the sequence of amino acids in the protein chain.

The secondary structure refers to how it folds up into strutures called alpha helices and beta sheets. Beta sheets give strength to spiders webs. 

Tertiary structure refers to the 3D shape of the overall folded-up protein chain. Tertiary structure of GFP origianlly from a jelly fish, now commonly used in transgenic animals. 

Quaternary structure of a protein refers to proteins composed of different sub-units joined together. A good example is haemoglobin. It has 4 protein sub-units.

Types of protein: chitin- arthropod exoskeletons, cartilage- shark skeletons, keratin- hair and claws, collagen- skin and connecive tissue. 

Venom toxins: atracotoxins, latrotoxins, agatoxins, bungarotoxins.

Protein channels: allow things to…