Amino acids Flashcards Preview

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Flashcards in Amino acids Deck (21):
1

define: a-amino acid

NH2 on the same carbon as COOH

2

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

all but one (glycine - H R group)

3

how many aa's have d confi?

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

4

describe aa structure

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

5

aa's are most accurately represented as

zwitterions

6

define: isoelectric point

pH at which most aa's are in zwitterion form

7

describe how electrophoresis of aa's relates to pH

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

8

pI (isoelectric point) calculation?

1/2(pKa1 + pKa2)

9

define: peptide

short polymer of aa's joined by peptide bond

10

whats peptide bond

C-N in the condensation polymerised aa

11

define: polypeptide

multiple aa's joined by peptide bonds

12

define: protein

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

13

ways we determine sequence of aas

cyanogen bromide
enzyme catalysis
edman degradation

14

escribe cyanongen bromide

cleaves peptide bond formed by COOH of methionine

15

describe enzyme catalysis

hydrolyse specific bonds at cOOH
-trypsin: COOHs of arginine and lysine
-chymotrypsin: cleaves phenylalanine, tyrosine, tryptophan

16

describe edman degradation

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

17

priamry structure

sequence of aa's contains peptide bonds

18

describe tertiary structure

overall folding pattern and arrangement of all atoms in a single pp chain
-by R groups
-cysteine reaction is reversible

19

define: quaternary structure

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

20

describe secondary structure

localised folding and coiling of pp chains

21

more on secondary strucutre?

yes