9.1 Proteins

functions

enzymes: speed up chemical reaction

• pepsin, DNA polymerase

structure: keratin, collagen

carriers/transporters

• hemoglobin

cell communication

• signals (insulin, hormones)

• receptors

defense: antibodies

movement (actin, myosin)

protein structure

monomers: amino acids

                                        side chain (R)

                                                |

amine group (H-N-H) — central carbon — carboxyl group (O=C-OH)

                                                |

                                                H

amino acid table

• 64 possible combos, only 20 amino acids

• kinda redundant 

polymers: polypeptides

AA bonds through dehydration synthesis

• peptide bond: covalent bond found in proteins

side chains

• nonpolar, hydrophobic (lots of CH)

• polar, hydrophilic (OH & N; bond w/ e/o or water)

• charged, hydrophilic

  • acidic: negatively charged H+ donors

  • basic: positively charged H+ acceptors

protein structure 1⁰

primary: order of AA in chain

beads on a string

single change can have big effects

stabilizer: peptide bonds

protein structure 2⁰

secondary: local folding into alpha helices and beta pleated sheets

waves or coils

stabilzer: H bonds btw carboxyl and amine

protein structure 3⁰

Tertiary: interactions btw distant amino acids

3D shapes

nonpolar cluster inwards

stanilizer: h bonds, ionic bonds, disulphide bridges

protein structure 4⁰

quaternary: more than one polypeptide chain bonded together

denaturation

unfolding

disruptions in H and ionic bonds

• temp, pH, salinity

destroys functionality

some can refold