Protein chemistry lecture 2

Question 1

Peptide bond

Answer 1

This is formed through a reaction with an amide group and carbonyl group resulting in a 50% double bond character bond. The molecule formed mainly exists in a planar cis conformation.

Question 2

Hydrolysis of peptide bonds

Answer 2

Can be hydrolyzed in a very slow manner unless in the presence of an enzyme. Amide bonds can spontaneously hydrolyze break off and disperse into ammonia in many situations (what are these situations?).

Question 3

Isopeptide bond formation

Answer 3

Glutamine/lysine and asparagine when in contact with one another form peptide bonds to one another creating an isopeptide bond and an ammonia side group.

Question 4

Reactions of sulfhydral groups

Answer 4

1. Acid base reaction: A cystiene group is deprotonated resulting in the production of thiolate anion a highly reactive nucelophile
2. Disulfide bond formation-sulfide molecules bond together when adjacent in space (even if far apart in seq.) and a disulfide bond is formed stabalizing the molecule.
3. Reacts with oxygen to produce a so2 group compound which dissociates and becomes a charged molecule

Question 5

Dehydroalanine reactions

Answer 5

OH group comes in and deprotonates an H group leading to the break of a sulfhydral group a formation of a double bond between two carbon atoms making it highly reactive. Lysine, cystiene and or amino groups can add across it and crosslink with it.

Question 6

Mailard browning reactions

Answer 6

carbonyl reacts with amino group to form a shiff base which undergoes multiple rearrangments producing various flavor compounds

Question 7

Protein polymers

Answer 7

long sequence of amino acids which are the same if encoded by the same gene

Question 8

Polypeptide chain and entropy

Answer 8

Protein chains are very flexible and can fold into a variety of conformations but in order to fold, the protein chain requires energy to overcome entropy which causes it to be in an unfolded state.

Question 9

Beta and alpha structure

Answer 9

Alpha-Right handed helical, side chains stick out and are bonded together by H bonds.

Beta sheets- two types, parallel and antiparralel stabalized by h bonds

Question 10

dihedral angles

Answer 10

3 bonds arranged in angles that provide for the specific orientation of amino acids in space