Proteins

1. Proteins

2. Are the enzymes that catalyse all biochemical reactions in the body. • Are the structure of the body • Carry oxygen • Fight disease • Make up cell membranes • Are chemical messengers

3. Structure of proteins • Are polymers • (note: often confusion over peptides, proteins and polypeptides = all are amino acid chains, difference is length.) • Units are amino acids (made up from 64 nucleotide combinations)

4. 20 different amino acids therefore some amino acids are specified by more than one codon. This is called degeneracy. This buffers against mutations as a single base change may not result in an affect • Are joined together by condensation • Some hydrophilic and some hydrophobic allowing proteins fold into specific shapes.

5. Fibrous proteins and globular proteins (long and stringy or round and ball like). • AUG is always the start signal • Stop signals always come at the end –UAA,UGA,UAG • Read amino acid tables for mRNA code: read left hand side, top and then right side.

6. So remember: • DNA: ATG CTG AGG GGT TAT TAA • TAC GAC TCC CCA ATA ATT • mRNA: AUG CUG AGG GGU UAU UAA • Don’t forget – U not T in RNA, read amino acid code from mRNA.

7. Protein structure and Function • There are four levels of protein structure. • The final shape of the protein determines its function. • For enzymes, the shape is crucial for correct function.

8. Primary structure = order of amino acids • Secondary structure = how tight the coil or chain is • Tertiary structure = how the chains loop back on themselves again and again. • Quaternary structure = how separate protein molecules join to each other.