Life’s Little Regulators ENZYMES Life’s Little Regulators Ch. 2.4

Definition of Enzymes….. Most drugs inhibit enzymes in the body!!! Thought Questions Examples of Enzymes…. Definition of Enzymes….. Most drugs inhibit enzymes in the body!!!

ENZYME Molecule, usually protein, that acts as a biological catalyst. The name of an enzyme usually ends in –ase. CATALYST Substance that speeds up a reaction but is not changed or used up by that reaction. Can be used over and over again.

“Finished” protein is an enzyme! Enzyme Manufacture Enzymes are made by protein synthesis DNA in the nucleus is transcribed into RNA Ribosomes are assembled in the cytoplasm Protein is made at the ribosome & enters the ER Protein is “finished” in the Golgi “Finished” protein is an enzyme! (but remember, not all proteins are enzymes!)

Where are enzymes? Enzymes are usually in cells. They can be: proteins in the cytoplasm proteins in an organelle proteins in the membranes of cells or organelles. Enzymes can also be secreted by cells into an organism’s body, such as those in your mouth, your stomach, and your intestines.

How an enzyme works: Vocabulary: Active site – place on an enzyme where another molecule bonds and is changed - what “disappears” when an enzyme is denatured (more to come…) Substrate – the molecule that bonds to the enzyme and is changed by the reaction there; the reactant

enzyme

How an enzyme works 1. The substrate and the enzyme bond together. 2. A reaction occurs that changes the substrate to something new (a product). 3. The enzyme is not changed and reacts again with a new substrate molecule.

Enzymes and substrates fit together more like a “handshake” Enzymes and substrates fit together more like a “handshake”. Each slightly changing to make the fit better once they contact each other.

http://www.hillstrath.on.ca/moffatt/bio3a/digestive/enzanim.htm

“Real” Example *Pepsin is an enzyme in the stomach. Protein is the substrate. Amino acids are the products.

Enzymes are sensitive to their environment. *denatured enzymes – when enzymes lose their structure so they don’t work; called denatured

Notice the process is often reversible when favorable conditions are re-established.

*Enzymes will not work right if: *pH too low or too high (lysosomes, your stomach, your small intestine) *temperature too high (or sometimes too low); (fever) *there are other causes, too.

Reaction Rate How fast the reaction occurs. In “real life” enzymatic reactions happen at the rate of thousands of times per second, per enzyme molecule! There are thousands of enzyme molecules per cell and trillions of cells!!!!!!

Reaction rate can be affected by many things. Increasing temperature increases reaction rate. Increasing concentration increases reaction rate. (Increasing concentration means adding more substrate or more enzyme.) Reaction rate can be measured by measuring how fast a product is formed or a substrate (reactant) is used up.

How does an enzyme affect the reaction rate? Enzymes make reactions happen easier. For a living organism, this means the reaction takes less energy to get started. The energy needed to get a reaction started is called the activation energy. Enzymes lower the activation energy.

Some enzyme reactions are slowed down by molecules called inhibitors.

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/11enzymes/03enzymes_b/index.shtml

Summary: http://www.kscience.co.uk/animations/model.swf Enzymes are proteins that act as catalysts. Catalysts are molecules that speed up reactions without being changed or used up. Enzymes have an active site where the substrate binds to form the product. Enzymes can be denatured by changes in the environment. Enzymes work by lowering the activation energy of the reaction. http://www.kscience.co.uk/animations/model.swf