Proteins

Question 0

What is the Henderson-Hasselbach equation?

Answer 0

pH=pKa+log(A/HA)

Question 1

What is pKa?

Answer 1

The pH at which an acid is 50% ionised/dissociated

Question 2

If the pH is two units less than the pKa how much of the acid will be ionised?

Answer 2

<1% will be ionised

Question 3

If the pH is one unit more than the pKa to what extent is the acid ionised

Answer 3

About 99% ionised

Question 4

If the pH is two units less than the pKa what is the extent of ionisation if the base?

Answer 4

About 99% ionised

Question 5

If the pH is one unit more than the pKa what is the extent of ionisation of the base?

Answer 5

About 10% ionised

Question 6

What is the main buffer system in the body and how does it work?

Answer 6

Carbonic anhydride buffers the pH of the blood
It catalyses the reaction between carbon dioxide and water in parietal cells in the gastric glands of the stomach
CO2 is reacted with water to form carbonic acid which dissociates to form H ions (transported to the stomach) and HCO3- (exported back into blood plasma)
Cl ions are transported out if the blood to balance charge (H + Cl to the stomach)

Question 7

How is pH important in drug uptake?

Answer 7

Weak acid/base drugs will dissociate in water to some extent the prevailing pH determines the extent of the dissociation
Charged species cannot spontaneously cross membranes

Question 8

What fractures effect the possible binding of protein partners ?

Answer 8

Availability
Co localisation
Complementary interactions
Competition from other partners

Question 9

Name some post translational modification of proteins

Answer 9

Methylation
Hydroxylation
Phosphorylation
Acetylation

Question 10

What is the Beer-Lambert equation?

Answer 10

A=Ecl

Question 11

What GFP?

Answer 11

Green fluorescent protein

Used as a biosensor for gene expression

Question 12

What is the Michaelis-Menten equation?

Answer 12

V0=Vmax[S]/Km+[S]
Or
V0=(kcat[E]t)[S]/Km+[S]

Question 13

What is the Lineweaver-Burke equation?

Answer 13

1/V0=Km/Vmax[S]+1/Vmax

Question 14

How will a competitive inhibitor affect the Lineweaver-Burke plot?

Answer 14

The x axis interception will become closer to zero

ie. -1/Km will be closer to zero

Question 15

How will a non competitive inhibitor effect the Lineweaver-Burke plot?

Answer 15

The y intercept increases

ie. The 1/Vmax increases

Question 16

What is ELISA?

Answer 16

Enzyme linked immune sorbant assay
Bond specific primary antibody to the protein target
Bind generic enzyme-labelled secondary antibody
Detect via enzyme activity

Question 17

What is the difference between a Native and SDS PAGE?

Answer 17

SDS denatures the protein and separates the proteins when the radius and chain length is proportional
Native does not denature

Question 18

How would you use electrophoresis to deprecate on charge?

Answer 18

Isoelectric focusing
A pH gradient is set up after the electric field is applied (an ampholyte solution is incorporated in the gel)
Proteins are distributed along the pH gradient according to their pI values

Question 19

What is an isoenzyme? Give an example.

Answer 19

Different tissues have different forms of the same enzyme
Eg. Lactate dehydrogenase
Tetramer with two possible sub units the combination varies in some tissues (muscle and heart/liver)
The presence of these isoforms in a patients sera shows where the damage has occurred

Question 20

What is immunoprecipitation?

Answer 20

Precipitation a protein antigen out of solution using a complementary specific antibody

Question 21

What is FRET?

Answer 21

Fluorescence resonance energy transfer
Tests which proteins are co localised and therefore associated with each other
Violet light is absorbed and retransmitted as blue light by a blue tagged protein, another green tagged protein absorbs and retransmits this light as green light which is detected