IAS05

Question 1

protein functions

Answer 1

catalyse reactions, involved in nucleic acid interactions, act as receptors, provide structure, in immune system

Question 2

insulin receptor structure

Answer 2

2 comp. subunits alpha & beta (21 & 30 AA), both alpha helix
3 disulfide bonds

Question 3

insulin receptor function (OPTIONAL)

Answer 3

binds insulin -> extracellular then intercellular domain changes conformation -> cause glucose carriers to move to cell membrane after long signal cascade -> more glucose shuttles into muscle / liver cell

Question 4

alpha amino acid definition

Answer 4

molecule containing amine & carboxyl group
alpha: amine attached to alpha carbon
21 proteinogenic, many others

Question 5

amino acid chirality

Answer 5

4 groups attached to carbon -> chiral -> AA enantiomeric, mirror image different from e.o.
body uses L-alpha AA
L determined by CORN (H pointing towards you) clockwise

Question 6

ionizations of AA

Answer 6

normal body aq conditions: both amino & carboxyl groups ionise (amino protonate, carboxyl deprotonate) to form zwitterion

Question 7

AA mnemonics

Answer 7

(Nonpolar) Grandma Always Visits London In May For Winston’s Party: Glycine Alanine Valine Leucine Isoleucine (Ile) Methionine Phenylalanine Tryptophan (Trp) Proline
(Polar) Santa Team Crafts Yearly New Quilts: Serine Threonine Cysteine Tyrosine Asparagine (Asn) Glutamine (Gln)
(+ve Charge) Knights Ride Horses: Lysine Arginine Histidine
(-ve Charge) DE: Aspartate Glutamate
Selenocysteine

Question 8

Aromatic AA, polar AA

Answer 8

Aromatic: HTTP
280nm absorption peak allows direct protein conc. measurement
Polar: STCYNQ
hydrophilic & usually on protein surface

Question 9

Cysteine

Answer 9

forms disulfide bonds w/ e.o. -> oxidized to cystine in extracellular env.
selenocysteine cannot

Question 10

peptide bond

Answer 10

condensation, forms peptide & lose water
peptide backbone in PP (<100AA), protein (>100)

Question 11

protein struc orders

Answer 11

primary: AA sequence (N->C) incl. posttranslational modification e.g. phosphorylation, glycosylation, hydroxylation
secondary: alpha helix, beta sheet
tertiary: folded chain, protein struc e.g. myoglobin
quaternary: 2+ PP / subunits join together e.g. haemoglobin

Question 12

secondary structure

Answer 12

alpha helix beta sheet, both H bond stabilized
alpha: RH helix, side chains protrude out of spiral
beta: 2+ strands, pleated structure, can be parallel or antipa., protrude out of sheets

Question 13

secondary vs tertiary

Answer 13

secondary: due to backbone atom interactions, local conf
tertiary: due to side chain interactions, global conf, interactions may be H bond, VDW, electrostatic attraction