BRANDI AND ZAK

Secondary Structure Can fold and align them selves and the repeating pattern is called a secondary structure. Common structures are the helix and pleated sheet

Alpha helix Single protein chain twisted Held together by intermolecular hydrogen bonds These bonds are located between the back bone –c=o and H-N- groups. All amino chains point out words from the helix.

Alpha Helix

Beta pleated sheet Held together by either intermolecular or intramolecular hydrogen bonds. Sheets occur between molecules when polypeptide chains run parallel or antiparallel. In Intramolecular the polypeptide chains a U-turn or hairpin structure is antiparallel.

Beta pleated sheet

Random coils They make up most proteins. These are when there is no repeating pattern Many globular proteins have all three kinds

Random Protein coils

keratin Fibrous protein in hair, finger nails, horns, and wool. Fibroin is the structure in silk. Silk worms and spiders have unmatched tensile strength because the pleated sheets are made up of alanine and glycine.

Keratin

Extended helix Collagens extended helix is the protein in connective tissues that provides strength and elasticity. Makes up to 30% of a humans weight.

14.10 tertiary structure Is a 3d arrangement in every atom molecule. Covalent bonds are most often involved in stabilization of tertiary structures in disulfide bonds. When cysteine residues on two different chains can form a covalent linkage.

tertiary structure

Hydrogen bonding Secondary structures stabilize –H bonding between backbone –C=O and –N-H groups. Tertiary structures are stabilized by –H bonding between polar groups on side chains and peptide backbone.

Salt bridges Is also known as electrostatic attractions This happen between 2 amino acids with ionized side chains This happen between an acidic amino and a basic amino acids Acidic is –coo Basic is –NH 3 or =NH 2

Salt bridges

Hydrophobic Interactions When in aqueous solutions, golbular proteins usually turn outward, to the aqueous solvent, with the nonpolar group inward to avoid the water. Nonpolar groups prefer interaction with each other, with no water in these areas. Not as strong of a bond as a salt bridge or hydrogen bonding These interactions take place over large surface areas making it’s a collectively strong enough to stabilize a loop or tertiary structure.

Metal ion coordination Two side chains with the same charge usually repel each other, but can be linked by metal ions. This is why certain trace metals are needed in the body.

chaperones Some chains can only fold in one way, but polypeptides can fold in many ways. Chaperones are found in living cells, these proteins help newly synthesized polypeptides chains to become secondary or tertiary structures.

Quaternary structure is the highest level of protein organization. This applies to proteins with one or more polypeptide chain. Quaternary structure determinds how the different subunits of proteins fit into an organized unit. Subunits are held together by hydrogen bonds, salt bridges and hydrophobic interactions.

Hemoglobin Made of four chains called globins Each chain is surrounded by iron-containing heme unit. Conjugated proteins contain the non-amino acid portions. Prosthetic groups are the non amino acids.

collagen A high organizations of subunits is see in collagen. This contains a triple helix called tropocollagen. This is only found in fetal or young connective tissues. As it ages it forms insoluble cross-linking, which contain ionic bonds.

Integral Membrane Proteins Its estimated the 1/3of all proteins are Integral membrane. To be stable in the non-polar environment of the lipid bilayer, it forms quaternary structures so the outer surface of the nonpolar and interacts with the bilayer. This causes most proteins to be turned in ward.

14.12 Denaturation is when any physical or chemical agent destroys stabilizing structures. An example is if you boil collagen the triple helix will disappear. The breaking of bonds can cause the globular bonds to un fold. Deagents cause proteins to change by opening up hydrophobic regions

2-mercaptoethanol Reducing agents like this can break –S-S disulfide bonds, making –SH groups. This process can permanently straighten or curl hair. When the agent is applied it causes to the molecules to become flexible so the hair can be set to the desired shape. When the oxidizing is applied and hardens them again by creating new disulfide bonds.

Heavy metals Heavy metals also denature proteins by attracting -SH groups. The antidotes takes advantage of this, milk and eggs are denatured the same way causing insoluble precipitates in the stomach. The precipitates must be removed or else the poisonous metals will be digested and sent in to the blood stream. b

alcohol Alcohol is also used to denature proteins, this is how you sterilize the skin. 70% ethanol penetrates bacteria and kills them by coagulating their proteins 95% only denatures surface proteins.