Cofactors and enzyme inhibition

What do inorganic cofactors do ?

Help the enzyme and substrate to bind together

What happens with inorganic cofactors in the reaction ?

They don’t directly participate in the reaction , and are not used up or changed in any way

What are inorganic cofactors ?

Inorganic molecules or ions

What is an example of an inorganic cofactor ?

Chloride ions are organic cofactors for the enzyme amylase

What do organic cofactors do ?

They act as carriers , moving chemical groups between different enzymes

What happens with organic cofactors in the reaction ?

They participate in the reaction and are changed by it

What are organic cofactors ?

Organic molecules (coenzymes )

What is an example of an organic cofactor ?

The coenzyme NAD is derived from the vitamin B3

What do coenzymes do ?

Bind tightly to and form a feature of a protein/ enzyme

They are vital to the function of the enzyme molecule

What are prosthetic groups ?

Organic groups the form a permanent attachment to the enzyme

What is an example of a prosthetic group ?

Zinc ions become part of the carbonic anhydrase. This is an enzyme required for the metabolism of Carbon Dioxide .

How are prosthetic groups similar to inorganic cofactors ?

Both bind to enzymes to activate them , cofactors bind loosely but prosthetic groups bind tightly .

What do competitive inhibitors do ? 

Compete with the substrate to bind with the active site . They therefore block the active site , and no reaction happens

What shape are competitive inhibitors ?

A similar shape to the substrate

What does the amount of inhabitation and the rate of reaction depend on ?

Concentration of substrate

Concentration of inhibitor

What happens if there is a high concentration of competitive inhibitor ?

The inhibitors will take the active sites , and the substrate will be unable to be catalysed 

What happens if there is a high concentration of substrate with competitive inhibitors ?

Increases the chance of the substrate getting to the active site before the inhibitor

Are reactions with competitive inhibitors reversible or not ?

They are reversible so the reaction will eventually be catalysed - but at a slower rate

What do non-competitive inhibitors do ?

Bind to the allosteric site which causes the active site to change shape , so the substrate can’t bind to it 

What happens when you increase substrate concentration with non-competitive inhibitors ?

No effect, enzyme activity will still be inhibited

Are reactions with non-competitive inhibitors reversible or not ?

Non-reversible , therefore enzyme activity will stop

What makes a reaction reversible or non-reversible ?

Depends on the strength of bonds between the enzyme and inhibitor

How is a reaction irreversible ?

String covalent bonds mean the inhibitor can’t be removed easily 

How is a reaction reversible ?

There are weaker hydrogen or ionic bonds , which means the inhibitor can be removed