ch3 - amino acids and proteins

what are amino acids and what are proteins

amino acids are monomers that join to form the polymer proteins

what is the general structure of amino acids on the sides and middle

amine group = NH2

carboxyl group = COOH

middle = variable R group, C and H

what dies it mean by a variable R group

there are 20 different possible R groups which means there are 20 different possible amino acids

what is another name for the R group

side chain

what is a peptide

when two or more amino acids are joined together by peptide bonds

how does a peptide form and what by-product is formed as a result

OH (on carboxyl group of one amino acid) reacts with the H (on amine group of another amino acid) forming a peptide bond which joins them together

> this process is a condensation reaction which forms H2O as a by-product

what is a polypeptide

when many amino acids are joined together by peptide bonds forming a chain

what is the primary structure and why is it so important for the final protein produced

the sequence of amino acids in the polypeptide chain

> the order in which amino acids are specifically in is determined by information in DNA

importance = the primary structure determines final 3D structure anf function of a protein

if a mutation occurs in DNA what impact can it have on the primary structure

> doesnt always have an impact because different codons (different combinations of triplet of bases) can code for the same amino acid

> if it does have impact it will change the order amino acids are organised in the polypeptide changing the final 3D structure and function

what is the secondary structure

when the polypeptide chain is folded into an alpha helix OR beta pleated sheet depending on the sequence and order of amino acids

what bonds form in the secondary structure

hydrogen bonds will form between the CO (on carboxyl group of one amino acid) and the H (on amine group of another amino acid)

why is it that these hydrogen bonds can form between the amino acids in the same polypeptide chain

because now that the polypeptide chain is folded into either alpha helix or beta pleated sheet the amino acids are close to each other

what is the tertiary structure and how many interactions can be involved to hold it together

when the alpha helix OR beta pleated sheet folds into 3D structure which are held by 4 possible interactions between the R groups of different amino acids

name the 4 possible interactions that can form between the R groups of different amino acids

-weak hydrogen bonds between polar (slightly charged) R groups

-strong ionic bonds between charged (+ve or -ve charged) R groups

-strong covalent disulphide bridges ONLY between R groups of an amino acid that contains sulphur, ONLY cysteine

-hydrophobic and hydrophilic interactions

» hydrophilic = turns out to interact with water

» hydrophobic = turns inside into the center, away from water

what is the quaternary protein

only formed by large proteins where multiple polypeptide chains are linked together by the 4 possible interactions in the TS

in the quaternary structure do the 4 possible interactions form between R groups in = same polypeptide chain OR

between R groups in = different polypeptide chains

between R groups of amino acids in different polypeptide chains

what is the difference in number of polypeptide chains in tertiary proteins and quaternary proteins

tertiary = ONLY 1 polypeptide chain

quaternary = MULTIPLE polypeptide chains