Cofactors and Inhibitors Looking at enzymes more closely

Cofactors

•  Nonprotein helpers that help catalyze reactions

•  Can either bind loosely or permanently on the substrate

•  If the cofactor is organic, it is considered a coenzyme

Vitamins are coenzymes

Vitamins are coenzymes Vitamin C (Ascorbic Acid) - Assists in the development of Healthy immune system

Vitamin D- helps the absorption of calcium in blood, and production of phagocytes

Rickets disease

Scurvy

Folic Acid - assist in the development of spinal cord during embryonic stage

Spinal bifida

Enzyme Inhibitors

•  Selectively inhibits activity of certain enzymes

•  Can have a permanent effect on the enzyme, and can be irreversible.

•  There are two types: competitive and non-competitive

Competitive Inhibitors

•  Resembles much like the substrates •  Blocks substrates from binding to active

sites of enzymes •  How do you think you can reverse this?

Take an enzyme supplement

Noncompetitive Inhibitors

•  Impede enzymatic reactions by binding on a part of the enzyme

•  Causes enzyme to change shape. •  How does this affect catalytic reactions?

It can slow down, or won’t happen at all because the enzymes are denatured.

Example of noncompetitive inhibitor

•  Sarin, a nerve gas

Serine, found on the active site of acetylcholinesterase, an enzyme of the nervous system

Example 2 of noncompetitive inhibitor

DD-transpeptidase

Penicillin

Development of penicillinase

Homework Today: Let’s Review

Respond to the following question using the notes you took in class: Enzymes that work inside cells are sometimes affected by non-competitive inhibitors. Explain how a non-competitive inhibitor affects the activity of an enzyme.

If the inhibitor attaches to the enzyme the enzyme will change shape making it denatured and so the reaction will not occur. And example of a non competitive inhibitor is Sarin. Sarin is a nerve gas and if inhaled in large amounts, can be deadly. Sarin paralizes your muscles making it impossible for breathing, and you brain won’t be able to send messages to your heart to pump blood.

DDT as a noncompetitive inhibitor

Do Now (Not Later) •  Pick up today’s handout at the front of

the room •  Copy homework due Thursday: Study

for Exam on Thursday •  Note in Schedule: ALL IB Bio Classes

for NEXT Thursday (12/10) report to see Group 4 Presentations – you will be accountable for an assignment on it afterwards.

•  This is when a protein’s function at one site is affected by the binding of a regulatory molecule.

An enzyme prone to allosteric regulation has 2 or more protein subunits

Each subunit has an active site

If one unit changes, everything else does too

Active Form

This type of enzyme oscillates between 2 different shapes, depending on what types of ligand that binds to it

Non-Active form

This type of enzyme oscillates between 2 different shapes, depending on what types of ligand that binds to it

These ligands are usually ATP or ADP molecules

Substrate

Enzyme

The ligand can stimulate catalytic activity in the enzyme

by binding to the substrate, which forces the enzyme to activate

through induction.

Ligand Regulator

Hemoglobin functions through cooperativity

Oxygen binding on just one subunit can increase the infinity to oxygen for all other subunits.

This is why there are more hemoglobin in areas of the body where respiration is needed most

•  Allosteric regulation makes sure that our body does not produce too much of one thing.

•  How it works: the product itself attaches to the first enzyme in the chain and inhibits the chain of reactions until they need to produce more of that product.

•  Noncompetitive inhibition can be positive or negative depending on the type of ligands (ex: external ligands vs. internal ligands).

Homework Assignment •  Complete both worksheets. Use today’s and

yesterday’s notes to help you, as well as pages in the textbook.

•  Bring materials for your enzyme lab tomorrow.

•  If there is a snow day tomorrow, homework will be due on Thursday. Check your email for any class updates.

When you have finished copying down homework, put everything away. We need to talk about something serious.