ch4 - inhibitors and cofactors

What is an inhibitor

A molecule that binds to an enzyme and reduces its activity

What 2 terms are used if an enzyme inhibitor is permanent or not 

Reversible 

Non reversible 

What is the effect of a reversible enzyme inhibitor 

Forms weak bonds with enzymes - binds temporary and can detach 

What is the effect of a non reversible enzyme inhibitor 

Forms strong bonds with enzymes - binds permanently and inactivates enzyme 

Name the 2 types/categories of enzyme inhibitors 

Competitive 

Noncompetitive

What is a competitive inhibitor 

a molecule with a similar shape to the substrate which binds to the active site of an enzyme 

How does a competitive inhibitor act 

CI competes with substrate for the same active site > less active sites available > less ES complex form > decreased rate of reaction 

Is a competitive inhibitor permanent or not 

Its reversible so only binds temporarily 

What happens when you increase substrate concentration 

increasing substrate conc > substrates will outcompete the CI > more substrates will bind to the active sites forming more ES complex > decreases effect of CI because

What is a non competitive inhibitor 

a molecule which binds to the allosteric site (different to the active site) of an enzyme 

How does a non competitive inhibitor act 

nonCI binds to allosteric site > tertiary structure of enzyme changes which causes shape of active site to change > active site is no longer complementary so substrate cannot bind > less ES complex form > decreased rate of reaction 

Is a non competitive inhibitor permanent or not 

Can be both reversible and non reversible - temporary or permanent 

What happens when you increase substrate concentration 

increasing substrate conc has NO effect since nonCI is not competing with substrates for the same active site 

What is end product inhibition 

When the final product created from a series of enzyme controlled reactions inhibits the first enzyme in the reaction 

How does end product inhibition work 

Final product binds to an allosteric site on the first enzyme changing the shape of the active site substrate can no longer bind 

> preventing more product forming

Why is end product inhibition known as negative feedback 

high concentrations of the final product would lead to a decrease in its own product formation 

What is a cofactor

A non protein substance which binds to an enzyme, helping the enzyme carry out its function 

Why are cofactors so useful for enzymes 

increase the rate of reaction of an enzyme

Name an example of a cofactor and state what enzyme this is for 

Cl- is a cofactor for amylase enzyme

Name the two types of cofactors 

Coenzymes 
Prosthetic groups 

What is a coenzyme and what is its function 

A type of cofactor that binds temporarily to an enzyme - it is organic and usually derived from vitamins 

Function - to transfer chemical groups e.g. H+ atoms and/or electrons from one molecule to another 

Name 3 examples of a coenzymes and their role 

NAD/ FAD - transfer H+ atoms and electrons to electron transport chain 

Coenzyme A - transfers acetyl group

What is a prosthetic group 

A type of cofactors permanently bound to an enzyme

Name an example of a prosthetic group

Haem group in haemoglobin which contains Fe²⁺ (Iron II) which binds reversibly to O2 to transport it around the body