Rafferty 1

Question 1

define and give the equation for pI (where there are 2pK values)

Answer 1

pI is the zwitterionic form of an amino acid. (pK1+pK2)/2=pKI

Question 2

give the henderson-hasselbalch equation

Answer 2

pH=pKa+log([A-]/[HA])

Question 3

enzymes enhance the rate to go to the e_______ point

Answer 3

equivalence

Question 4

do enzymes increase or decrease the energy barrier for the forward and backward reactions?

Answer 4

decrease

Question 5

what is an apoenzyme and a holoenzyme? what is the equation that relate these two forms of enzyme?

Answer 5

apoenzyme = enzyme without cofactor
holoenzyme = enzyme with cofactor that is catalytically active
apoenzyme+cofactor=holoenzyme

Question 6

give the 2 types of cofactor

Answer 6

metals and coenzymes

Question 7

define a coenzyme

Answer 7

subdivision of a cofactor - small organic molecule

Question 8

give the 2 types of coenzyme and define them

Answer 8

cosubstrate - loosely bound coenzyme (binds and is released from enzyme like substrate/product)
prosthetic group - tightly bound coenzyme

Question 9

define a cofactor

Answer 9

additional molecule that increases the number of available functional groups to aid catalysis

Question 10

name and describe the 6 types of enzyme

Answer 10

1. oxidoreductases: redox reactions eg by nad+
2. transferases: functional group transfer (1 e-philic group from 1 nucleophile to another)
3. hydrolases: specific transfer reaction via H2O addition
4. lyases: addition/removal of groups to make double bonds
5. isomerases: conversion between isomeric forms
6. ligases: joining two molecules, requires chem energy source

Question 11

what type of bond stabilizes IgG?

Answer 11

disulphide bridge

Question 12

name the 6 domains in IgG

Answer 12

VL/VH/CL1/CH1/CH2/CH3

Question 13

where to ab’s bind on IgG?

Answer 13

hypervariable beta-sheet loops on the N-terminal variable region

Question 14

name and quantify the number of regions in IgG, how can these regions be separated?

Answer 14

2xFab 1xFc, split by papain

Question 15

what are the 3 main functions of a membrane?

Answer 15

1. separate cells from env
2. internal membranes for boundaries of organelles
3. env for critical biological processes

Question 16

name the types of molecule that are membrane (im)permeable

Answer 16

permeable: gases/small uncharged polar (can be semi-permeable)
impermeable: large uncharged polar molecules/ions/polar molecules

Question 17

name 3 main types of lipid

Answer 17

phospholipids, isoprenoids and glycolipids

Question 18

which molecule can form a micelle?

Answer 18

fatty acids

Question 19

what does increasing the alcohol content of a phospholipid membrane do?

Answer 19

increases its curvature

Question 20

what is the effect of increasing double bond content in a fatty acid?

Answer 20

increases membrane fluidity

Question 21

what is the effect of asymmetric lipid distribution in a membrane?

Answer 21

changes in membrane curvature

Question 22

what is the effect of cholesterol in a membrane?

Answer 22

decreases fluidity - cholesterol has planar steroid ring which gives it mechanical stability
increased order - this is due to its planar, inflexible tail, which makes the phospholipids elongate - therefore increased membrane thickness

Question 23

what is the effect of increasing order in a phospholipid membrane?

Answer 23

membrane increases in thickness - this is because the f/a chains straighten

Question 24

what is the effect of increasing temperature in membrane containing cholesterol?

Answer 24

gel consistency becomes more fluid which decreases phospholipid order and therefore decreases in thickness

Question 25

what is FRAP?

Answer 25

fluorescence recovery after photobleaching - experiment to quantify lateral protein and lipid movement within a plasma membrane

Question 26

name and describe the 3 main membrane proteins

Answer 26

1. integral: all/partly embedded in membrane, h.phobic exterior, need v specific detergent to remove from membrane (called solubilization)
2. peripheral: at membrane boundary, interact with both other membrane proteins
3. lipid anchored: f/a anchored in membrane via ester/amide link to protein OR isoprenoid group in membrane attached by cys residue to protein OR GPI linked to protein via c-terminus

Question 27

why are alpha helices used in transmembrane proteins?

Answer 27

contain h.phobic residues

Question 28

what is a hydropathy plot and why is it used?

Answer 28

the calculation of a/a seq of a protein to determine h.philic/phobic nature

Question 29

name and describe the 3 transport proteins

Answer 29

1. channels and pores- molecules diffuse through, channel mediated (which is unlike simple diffusion)
2. passive transporters - with conc grad, carrier mediated
3. active transporters - against conc grad uses chem energy

Question 30

describe the linkages in the three lipid anchored proteins

Answer 30

lipid anchored:

• f/a anchored in membrane via ester/amide link to protein
• isoprenoid group in membrane attached by cys residue to protein
• GPI linked to protein via c-terminus