Chemical Reactions & Enzymes

1. Chemical Reactions & Enzymes

2. Chemical Reactions • A change of one set of chemicals into another • Can be slow or fast • Require collisions between molecules • Involves changes in chemical bonds

3. Chemical Reactions • Reactants: elements or compounds that enter into a chemical reaction • Bonds of reactants are broken in a chemical reaction! • Products: elements or compounds that are produced in a chemical reaction • Bonds of products are formed in a chemical reaction! What are the reactants in this reaction? The products?

4. Chemical reactions involve changes in chemical bonds! Whenever a reaction occurs that rearranges the atoms of molecules, bonds in the reactants must be broken & new bonds in the products must be formed.

5. Cells in your body produce CO2, then blood carries the CO2 from the cells to your lungs (you exhale it out!). Problem! • CO2 is not soluble (dissolvable) in water, so it cannot be carried through your blood! A chemical reaction in your body converts CO2 into a soluble compound!

6. In blood, CO2 is converted to a soluble compound: CO2 + H2O  H2CO3 In the lungs, the reaction is reversed to exhale the CO2: H2CO3  CO2 + H2O

7. Chemical reactions involve energy! • Breaking & forming chemical bonds requires energy release or absorption. • Reactions that release energy can occur spontaneously (but not all do)! • Energy is released as heat. • Reactions that absorb energy will not occur without an energy source!

8. Energy-Releasing Reaction Energy-Absorbing Reaction Activation energy Products Activation energy Reactants Reactants Products Activation Energy • The energy needed to get a reaction started • Some chemical reactions are very slow or require lots of energy, so they cannot occur on their own!

9. Energy-Releasing Reaction Energy-Absorbing Reaction Activation energy Products Activation energy Reactants Reactants Products Activation Energy Video Endergonic/Endothermic Exergonic/Exothermic

10. Energy-Releasing Reaction Energy-Absorbing Reaction Activation energy Products Activation energy Reactants Reactants Products Reactions • Endergonic: absorb free energy from the surroundings • Exergonic: have a net release of free energy • Can occur spontaneously!

11. Enzymes are catalysts! • Catalyst: substance that speeds up the rate of a chemical reaction by lowering the activation energy • Enzyme: protein that acts as a biological catalyst • Enzymes speed up reactions that take place in your cells!

12. Enzymes • Provide a site (the active site) where reactants can be brought together to react • This decreases the activation energy & creates the “enzyme-substrate” complex!

13. Enzymes • Substrate: the reactants in a reaction involving an enzyme • The substrate must fit completely into the active site in order for the reaction to take place! • Enzymes can be reused, but can only have 1 type of substrate!

14. Enzymes If enough substrate is present, a single enzyme can act on 1,000 molecules per second!

18. The enzyme-substrate relationship is like a lock & key! Only the correctly shaped key will open the lock…

19. Inhibitor Animation Enzymes can have an inhibitor in which another molecule can turn the enzyme on/off!

20. Inhibitors • Competitive Inhibitors: block the active site • Non-competitive Inhibitors: bind to another part of the enzyme, causing the shape of the active site to change making it useless

21. Inhibitors • Allosteric Inhibitors: enzymes naturally go from active to inactive • An activator will bind causing the active form of the protein to remain stable. • An inhibitor will stabilize the inactive form of the enzyme. An allosteric activator keeps the enzyme on. An allosteric inhibitor keeps the enzyme off.

22. Denaturing • When proteins lose their shape & functionality Every enzyme has an optimal condition at which it works best! If these conditions aren’t met, the enzyme will denature!

23. What causes enzymes to denature? • pH • Temperature • Other proteins • Chemicals

24. The sugar found in milk is called LACTOSE. • Lactose is a DISACCHARIDE! This means that lactose is made of 2 MONOSACCHARIDES – glucose & galactose! Remember! When you digest your food, your body breaks it up into its smallest subunits!

25. Do we need the enzyme lactase to digest milk (& the sugar in milk)? You are going to design an experiment to test this question!

26. When designing your experiment… • Remember to only change 1 variable at a time! • You will create a lab report (1 for the whole group), that needs to include: • Hypothesis • Materials used (be specific about quantities) • The procedure (I should be able to repeat your experiment) • Data & Results • Conclusion

27. Materials available to you: • Beakers, graduated cylinders, etc. • Whole milk • Lactase enzyme • In the form of a chewable tablet • Glucose test strips • They change colors if glucose is present. I WILL CHECK YOUR MATERIALS & PROCEDURE TODAY… YOU NEED MY APPROVAL!