Amino acids

Question 1

define: a-amino acid

Answer 1

NH2 on the same carbon as COOH

Question 2

how many aa’s havve atleast one stereocentre (ie are chiral)

Answer 2

all but one (glycine - H R group)

Question 3

how many aa’s have d confi?

Answer 3

all but 2 - cysteine has L, glycine doesnt have any.

Question 4

describe aa structure

Answer 4

R group - polar (also acidic and basic), non polar
H
COOH
NH2

Question 5

aa’s are most accurately represented as

Answer 5

zwitterions

Question 6

define: isoelectric point

Answer 6

pH at which most aa’s are in zwitterion form

Question 7

describe how electrophoresis of aa’s relates to pH

Answer 7

paper and +/- electrodes
dried and ninhydrin dye is aded to make aa's appear purple
-higher charge density = moves quicker
-goes to opposite pole
-zwitterions dont move

Question 8

pI (isoelectric point) calculation?

Answer 8

1/2(pKa1 + pKa2)

Question 9

define: peptide

Answer 9

short polymer of aa’s joined by peptide bond

Question 10

whats peptide bond

Answer 10

C-N in the condensation polymerised aa

Question 11

define: polypeptide

Answer 11

multiple aa’s joined by peptide bonds

Question 12

define: protein

Answer 12

biomacromolecule weighing atleast 5000gmol-1 and consists of atleast 1 pp chain

Question 13

ways we determine sequence of aas

Answer 13

cyanogen bromide
enzyme catalysis
edman degradation

Question 14

escribe cyanongen bromide

Answer 14

cleaves peptide bond formed by COOH of methionine

Question 15

describe enzyme catalysis

Answer 15

hydrolyse specific bonds at cOOH

• trypsin: COOHs of arginine and lysine
• chymotrypsin: cleaves phenylalanine, tyrosine, tryptophan

Question 16

describe edman degradation

Answer 16

identifies N terminal by attaching to N terminal of aa, cleaves itself and aa and aa’s identified. process repeats

Question 17

priamry structure

Answer 17

sequence of aa’s contains peptide bonds

Question 18

describe tertiary structure

Answer 18

overall folding pattern and arrangement of all atoms in a single pp chain

• by R groups
• cysteine reaction is reversible

Question 19

define: quaternary structure

Answer 19

arrangement of pp chains into a non covalently bonded aggregration: can include additional units (eg. haem)

Question 20

describe secondary structure

Answer 20

localised folding and coiling of pp chains

Question 21

more on secondary strucutre?

Answer 21

yes