ENZYME ACTION!!!

What are Enzymes?

• An enzyme is a biological catalyst. It speeds up a chemical reaction without being used up in the reaction or becoming part of the products.

• All enzymes are proteins with a very specific 3-D shape.

• A substrate is the molecule that the enzyme acts upon. The 3-D shape of the enzyme fits a substrate molecule like a lock and key – a perfect fit.

Induced-Fit Hypothesis

• Enzymes are flexible molecules and research shows that enzymes will often change the shape of the active site very slightly so that it is an even more precise fit for the substrate.

• This phenomenon is known as the induced-fit model of enzyme activity.

Enzyme Action

ENZYMES IN ACTIONhttp://www.youtube.com/watch?v=E-_r3omrnxw

Enzyme Action

Points to Remember…• Active Site & Substrate• Induced-fit Model• Activation Energy• Enzyme-Substrate Complex• Enzymes are Like Batman!!!

(Git R Done and Git Out!)

Is That You Robin?!?!• Enzymes may be

assisted by cofactors and coenzymes.

• Cofactors are non-protein groups.

• Coenzymes are organic cofactors.

• These entities may bind to the active site or the substrate to assist in enzyme activity.

ENZYME INHIBITION

Why End a Good Thing?

• Inhibit means stop! If enzyme action is critical to normal health, then why would we want to stop it?– Energy Efficiency – It requires energy to

build molecules or break them down.– Build up of Toxins – Some products are

great until their concentration gets too high – then they become toxic to the cell. (Too much of a good thing!)

Enzyme Inhibition

• There are two main categories of enzyme inhibition – competitive and noncompetitive.

• Competitive inhibition means the active site is being competed for by another molecule that is not the substrate.

• The enzyme can’t grab onto the substrate because it is occupied with a noncompetitive inhibitor that has a similar shape as the substrate – but not the perfect shape – no work is done.

Competitive Inhibition

Noncompetitive Inhibition

• Noncompetitive inhibition occurs when an inhibitor molecule binds to the enzyme at a site other than the active site.

• This binding of the inhibitor changes the

3-D shape of the active site and renders it useless.

Allosteric Regulation

• Allosteric regulation is a form of noncompetitive inhibition.

• Allosteric sites on the enzyme are used by regulatory molecules to binds to in order to control enzyme action.

• Inhibition – Inhibitor binds to allosteric site to stabilize inactive form of enzyme – active site not right!

• Activation – Activator binds to allosteric site and stabilizes the working form of the enzyme – active site is just right!

Allosteric Regulation

ALLOSTERIC REGULATIONhttp://www.youtube.com/watch?v=d5fDEUhjo-M

FEEDBACK INHIBITION• Feedback inhibition occurs when there is a chain

of reactions that must occur in order to achieve a final product.

• When enough product has been made, some of the surplus product goes back to an enzyme earlier in the chain and inhibits it.

• When the surplus product is used up by the cell – the product acting as an inhibitor will be consumed and open the pathway again.

FEEDBACK INHIBITION

FEEDBACK INHIBITIONhttp://www.youtube.com/watch?v=DHZtOKyMPRY

FIN