BI108 Proteins

Amino acids

building block molecules of proteins that are linked together with covalent bonds to form a chain

Electrically (fully) charged side chains (R-groups)

Hydrophilic

Form ionic bonds with atoms of opposite charge or attract ions of opposite charges

Look for electronegative elements/functional groups that ionize

Polar but uncharged (partially charged) side chains (R-groups)

Hydrophilic

Forms hydrogen bonds

Look for electronegative/functional groups

Non-polar side chains

Hydrophobic

Cluster together in an aqueous environment

Look for hydrocarbon chains

Cysteine

forms disulfide bridges (sulfhydryl group; terminal sulfur)

Glycine

Really small!!

Fourth bond off alpha carbon is a hydrogen

Can influence 3D shape

Proline

Really bulky!!

Side chain forms ring structure back to amino acid skeleton

Prevents tight folds and bends

Peptide bond

bonds between amino groups and carboxyl groups that join amino acids; covalent bonds

Primary structure

amino acid monomers are joined, forming polypeptide chains

Secondary structure

polypeptide chains may form ⍺ helices or β-pleated sheets

⍺ helices

R-groups in an stick out from the spiral → are free to interact with other parts of the same protein or with other molecules

Form barrel or tube-like structures

β-pleated sheets

Bended or pleated sheet-liked structure

N-H and C=O groups on either side stick out

Tertiary structure

polypeptides fold, forming specific shapes

Denaturation

protein unfolding

Quaternary structure

two or more polypeptides assemble to form larger protein molecules