Michaelmas week 8

Question 1

What is a katal?

Answer 1

The SI unit of catalytic activity, defined as activity of a catalyst in moles per second (amount of enzyme needed to catalyse rate of 1 mol substrate per second)

Question 2

What is an enzyme unit, u?

Answer 2

Amount of enzyme that catalyses 1 micromol substrate per minute

Question 3

What is a dalton?

Answer 3

Unit to express protein molecular weight, equivalent to 1 atomic mass unit

Question 4

%(v/v) =?

Answer 4

Vol solute/ total vol solution x 100 where solute is a liquid

Question 5

%(w/v) =?

Answer 5

Weight solute/total vol solution x100 where solute is solid

Question 6

What wavelengths light does NADH absorb and why?

What is the implication of this?

Answer 6

Aromatic, delocalised electron system
UV range around 340 nm
There is a change in absorbance when NAD+ –> NADH allowing direct product measurement

Question 7

delta A=?

Answer 7

E delta c L

Question 8

How can you convert from katal to units?

Katal activity normally around how much smaller

Answer 8

Activity in katals= activity in units / ( 10^6 x 60)

Katal activity around 10^7 times smaller

Question 9

What is a background activity assay?

Answer 9

Contains all components of assay with the exception of the enzyme
Measures amount of spontaneous reaction present

Question 10

Where are hexokinase and glucokinase found?

Answer 10

Hexokinase–> in muscle, low Km of ~ 0.1 mM, functions at full capacity for fight or flight
Glucokinase –> in liver, Km ~ 7.64 mM, enzyme function at 50% Vmax in normal blood glucose conc (5-7 mmol) and very slow at low conc (3mmol) to prioritise muscle glycolysis