Chemical Reactions and Enzymes

1. Chemical Reactions and Enzymes

2. Chemical Reactions Chemical Reaction – the process that changes one set of chemicals into another. • Chemical reactions involve the breaking of bonds in the reactants and the formation of new bonds in the products CO2 + H2O → H2CO3 Carbon dioxide and water form carbonic acid

3. Chemical Reactions • Reactants – elements or compounds that you start with, found on the left hand side of the reaction arrow. • Products – elements or compounds produced from the reactants, found on the right hand side of the reaction arrow. CO2 + H2O  H2CO3 Product Reactants

4. Energy in Chemical Reactions • Energy can be released or absorbed in chemical reactions. • Most chemical reactions require some initial input of energy in order to start the reaction; this is called the activation energy.

5. Catalysts A catalyst speeds up the rate of a reaction by lowering the amount of activation energy needed to start the reaction.

6. Enzymes • Enzymes are PROTEINS that act as biological catalysts. They speed up reactions in cells.

7. Enzyme-Substrate Complex • Enzymes provide a site for the reactants (substrates) to react. This site is called the activation site. • The activation site and the substrate have complementary shapes, similar to a lock & key.

8. Enzyme-Substrate Complex A lock will only accept one key just as an enzyme will only accept a specific substrate. After the substrates have bound to the activation site the substrates will react with one another. Once the reaction is complete then the products are released and the enzyme is free to bind additional reactants (substrates).

9. Enzyme-Substrate Complex If the substrates do not fit in the activation site then the reaction will not take place. Each enzyme is very specific. There are usually only 1 or two molecules that will the active sites exactly.

10. Rate of Enzyme Activity There are factors that can affect an enzyme: • Temperature • Each enzyme has an optimal temperature range. At low temperatures the enzyme works slowly At high temps they may denature (breakdown) and not work correctly.

11. Rate of Enzyme Activity 2. pH • There is an optimal pH for every enzyme to function at. (usually at 7, neutral pH) • Many enzymes become denatured at low pH levels (when acid is present). • However some enzymes, like those that work in the stomach, function very well in acidic environments

12. Rate of Enzyme Activity • Concentration of Substrate or Enzyme • The more substrate available, the faster the reaction tends to go • The more enzyme that is available, the faster the reaction tends to go

13. 4.Cofactors and Coenzymes • Help Enzymes work faster (like some minerals and vitamins) Example: Iron must be present in blood in order for it to pick up oxygen.

14. 5. Inhibitors Stop enzymes from doing their jobs Two types 1. Competitive inhibitors: look like the substrate and block the active site 2. Noncompetitive inhibitors: bind to the enzyme causing its shape to change, changing the active site. 14

15. Enzyme Competitive inhibitor Type 1: Competitive Inhibitors • Stop enzymes from doing their jobs. • Two types • Competitive inhibitors: look like the substrate and block the active site Substrate

16. Enzyme Noncompetitive Inhibitor Enzyme active site changed Type 2: Non Competitive Inhibitors 16 Substrate

17. Quiz!!! • There are 13 Questions! • It will count as a test grade • You can only use YOUR notes.

18. Name_______________________________________ pd.________ • 1.___ • 2.___ • 3.___ • 4.___ • 5.___ • 6.___ • 7.___ • 8.___ • 9. ___ • 10.___ • 11.___ 12. ________________________________________________ 13. ________________________________________________

19. 1.In 1953 Stanley Miller and Harold Urey designed and experiment to test the Primordial Soup Theory. What were Miller and Urey able to produce in their experiment. • Oxygen for heterotrophic organisms to survive • Single celled organisms • Photosynthetic bacteria • Organic molecules out of inorganic material

20. 2. What is a cell membrane mainly composed of? • Lipids • Nucleic acids • Carbohydrates • Proteins

21. 3. The graph above shows the reaction rates of two different reactions. Which of the following statements could explain the difference in the two reactions? • Reaction A is catalyzed by an enzyme • Reaction B is catalyzed by an enzyme • Reaction A occurs at a faster rate than Reaction B • Reaction A and reaction B have the same reaction rate

22. 4. Enzymes catalyze chemical reactions that keep cells alive. Imagine that a cell had no enzymes. How would having no enzymes affect the chemical reactions in the cell? They would happen too slowly to support cellular processes They would happen too rapidly to support cellular processes They would happen at the same rate as they do with enzymes They would happen normally, only they use different reactants

23. 5. Which statement best describes the specificity of the enzyme for the substrate in a chemical reaction? The suffix –ase is used to identify the specific enzyme- substrate pairing. The bonding sites of enzymes to substrates fit like pieces in a jigsaw puzzle. Cells use enzymes to manage cell metabolism. Enzymes created during protein synthesis.

24. 6. What are the monomers that make up complex carbohydrates? • Amino acids • Fatty acids • Monosaccharides • Nucleotides

25. 7. Diagram above shows how living organisms use enzymes in chemical reactions to release energy. How do enzymes affect the reactions in which they take part? • Most enzymes slow down chemical reactions • Enzymes are converted into products in the reaction • Enzymes increase the activation energy of reaction • Enzymes decrease the activation energy of the reaction

26. 8. The diagram above is a model of a cellular process called transcription. What class of biological molecules is represented in the diagram? • Carbohydrates • Nucleic acids • Lipids • Proteins

27. The diagram below represents a process that occurs In organisms. • 9. Which row in the chart indicates what 1 and 2 in the boxes could represent? A. A • B. B • C. C • D. D

28. 10. Many of the proteins in the human body are enzymes that catalyze chemical reactions. What is the relationship between enzymes and activation energy? • When an enzyme catalyzes a reaction, it increases the activation energy of the reaction. • When an enzyme catalyzes a reaction, it increases the activation energy of the product. • When an enzyme catalyzes a reaction, it decreases the activation energy of the reaction. • When an enzyme catalyzes a reaction, it does not affect the activation energy of the reaction

29. The sweet taste of freshly picked corn is due to the high sugar content in the kernels. Enzyme action converts about 50% of the sugar to starch within one day after picking. To preserve its sweetness, the freshly picked corn is immersed in boiling water for a few minutes, and then cooled. 11. Which statement most likely explains why the boiled corn kernels remain sweet? A. Boiling destroys sugar molecules so they cannot be converted to starch. B. Boiling kills a fungus on the corn that is needed to convert sugar to starch. C. Boiling activates the enzyme that converts amino acids to sugar. D. Boiling deactivates the enzyme responsible for converting sugar to starch.

30. 12. How does the presence of an enzyme affect the rate of a chemical reaction? 13. What 3 things can affect the rate at which an enzyme works?