Tutoring today at 3:15 Retakes starting tomorrow at 2:45 Do-Now

1. Tutoring today at 3:15 Retakes starting tomorrow at 2:45 Do-Now 1.) Name three chemical reactions taking place in your body right now.

2. Chapter 3: Enzymes INB Pg 28

3. Enzymes • Enzymes are protein molecules that act as biological catalysts • Catalyst: molecule that speeds up a chemical reaction and remains unchanged after rxn • Enzymes usually end in –ase • Virtually every metabolic rxn is catalyzed by an enzyme

4. Enzymes • Globular proteins • Precise 3D shape • Multiple chains • Hydrophilic R groups on outside = water soluble • Active site: region on an enzyme to which another molecule/molecules- called a substrate- can bind

5. Lock and Key Hypothesis • Idea that enzyme has a particular shape to which the substrate fits exactly • Substrate=key. Held in place by temporary bonds • Enzyme=lock

6. Lock and Key Hypothesis • Each type of enzyme will act on only one type of substrate molecule • Shape of active site will only allow one shape to fit • Enzyme is said to be specific for substrate

7. Induced Fit Hypothesis • Modified the lock and key hypothesis in 1959 • New evidence suggested that enzymes are more flexible than is suggested by a rigid lock and key • Basically same as lock and key, but adds the idea that the enzyme, and sometimes substrate, changes shape slightly as substrate enters enzyme

8. Induced Fit Hypothesis • Ensures a more perfect fit • Makes catalysis more efficient • http://www.youtube.com/watch?v=z8lG8X9ZvxQ

9. Catalysis • An enzyme may catalyze a reaction in which it joins together two peptides • An enzyme may catalyze a reaction in which the substrate molecule is split into two or more molecules

10. Catalysis • Enzyme-product complex is briefly formed before the release of products • Interaction between the R groups of the enzyme and the atoms of the substrate can break, or encourage formation of, bonds in the substrate molecule, forming products • When the rxn is complete, the products leave the active site • Enzyme is unchanged and ready to accept another substrate • Rate of rxn is extremely rapid

11. Lysozyme • Found in tears, saliva, and other secretions. Breaks the polysaccharide chains in the cell walls of bacteria http://www.youtube.com/watch?v=QXIe0jDTlT4

12. Enzymes • As catalysts, enzymes increase the rate at which chemical reactions occur • Most of the rxns in living things would be too slow w/o an enzyme to sustain life

13. Chemical Reactions • Energy needed to start reaction = activation energy • Enzymes work by lowering activation energy

14. Other ways to increase rxn rate • Increase concentration of substrate • Increase energy of reactants (heating) • Ex: Benedict’s test • Most rxns occur at temps higher than our body temp, which is why enzymes are necessary

15. Do Now 12/2 • WOD FORTHRIGHT(FORTH rite) adv./n. • directly forward; without hesitation; a straight path • Whenever I want a FORTHRIGHT opinion, I always ask my two-year-old son. • The boss asked everyone to be FORTHRIGHT at the company meeting. • When Kathy asked Mark if her dress made her look fat, she wasn’t expecting his answer to be so FORTHRIGHT. Compare and contrast the lock and key hypothesis with the induced fit hypothesis.

16. The course of a reaction • When enzyme and substrate are first mixed, there are a large number of substrate molecules • At any moment, virtually every enzyme molecule has a substrate in its active site

17. The course of a reaction • Initially, the rate at which a reaction occurs will depend only on how many enzyme molecules there are and the speed at which the enzyme can convert substrate into product • However, as more substrate is converted to product, there are fewer and fewer substrate molecules, which slows down the rate of reaction

18. The course of a reaction

19. The effect of enzyme concentration • Directly proportional to reaction rate • As we increase the concentration of an enzyme, we have more active sites available for the substrate. • As long as there is plenty of substrate available, the initial rate of reaction increases linearly with enzyme concentration

20. The effect of substrate concentration • As concentration of substrate increases, the initial rate also increases • If we continue increasing substrate concentration, it will eventually max out because there are no more available active sites • If more substrate is added, the enzyme simply cannot work faster. The enzyme is working at its maximum possible rate, known as Vmax(V=velocity)

21. Temperature and enzyme activity • Low temp=low particle movement. Substrate move very slowly and will not often collide with the active site • As temp increases, substrates move faster and collide with active site more. Reaction rate increases • At a certain temperature (specific for diff. enzymes), hydrogen bonds begin to break in the enzyme (remember, it is a protein) and the enzyme will denature (loose its structure and function)

22. Temperature and enzyme activity • Denaturing of an enzyme is often irreversible • Substrate cannot fit into denatured active sites, so no activity takes place • The temperature at which an enzyme catalyzes a reaction at the maximum rate is called the optimum temperature

23. Check your understanding • Proteases (enzymes that break down proteins) are used in biological washing powders. • How would a protease remove a blood stain on clothes? • Most biological washing powders are recommended for use at low washing temperature. Why is this?

24. Check your understanding • Hemoglobin is the colored pigment that causes blood stains. Protein-digesting enzymes hydrolyze hemoglobin to amino acids, which are colorless. They are also soluble, so will wash away in water. • Many protein-digesting enzymes have an optimum temperature of around 40 °C. If the temperature of a reaction is too high, the enzyme will denature.

25. pH and enzyme activity • pH is a measure of hydrogen ions in solution. The lower the pH, the higher the hydrogen ion solution. • Hydrogen can interact with R groups of amino acids which affects bonding in amino acids, which can change the structure (and function) of an enzyme • Enzymes work best under specific pH ranges.

26. homework • Page 64 #2, #6, #7, #9 • Quiz on enzymes (covered up to today) next class