IB Biology Quarter 1 Exam Review

1. IB Biology Quarter 1 Exam Review Topic 3.6 – Enzymes

2. Guidelines • Get into a group of 4 • Designate a recorder (you may rotate) • In order to get points, your answer must be written on the dry erase board • When time is called, each group will raise their answer/board up • If your answer is correct, award yourself a point (we’re on the honor policy ) • I will take away points for disruptive behavior • 1 minute per question

3. Topic 3.6 – Enzymes • Why are enzymes called biological catalysts? • Because they speed up the rate of a reaction. • Reactants in the presence of an enzyme will form products at a faster rate than without an enzyme

4. Topic 3.6 – Enzymes • Which macromolecule group do enzymes belong to? • Proteins • Made up of amino acids

5. Topic 3.6 – Enzymes • What do we call the reactant to which the enzyme binds? • Substrate

6. Topic 3.6 – Enzymes • True or false: The shape of an enzyme is very specific. • True

7. Topic 3.6 – Enzymes • Define: denaturation • When the specific shape the of the enzyme is changed, which alters the shape of the active site • The substrate and enzyme can no longer bond • Rate of reaction decreases

8. Topic 3.6 – Enzymes • Outline the lock and key hypothesis used for enzyme-substrate activity. • Lock = enzyme’s active site • Key = substrate • Because the shape of the enzyme is very specific, only one key (substrate will fit) • Enzymes and substrate are specific for each other

9. Topic 3.6 – Enzymes • Define: active site • The area on an enzyme that binds to the substrate • Specific area responsible for the activity of all enzymes/proteins

10. Topic 3.6 – Enzymes • Outline the induced fit model for enzyme-substrate activity. • The active site on the enzyme will slightly change its shape to form a tight bond with the substrate

11. Topic 3.6 – Enzymes • True or false: An enzyme can force a reaction to take place. • False • Enzymes cannot force reactions to occur that would not otherwise take place • Enzymes only speed up the rate of reaction.

12. Topic 3.6 – Enzymes • How do enzymes speed up the rate of reaction (think about activation energy) • The activation energy is the energy needed to start a reaction • Enzymes lower the activation energy • Reactants are broken down to products at a faster rate

13. Topic 3.6 – Enzymes • Why are small amounts of enzyme effective in catalyzing a reaction? • Enzymes are reusable • Once a substrate is converted to a product, the active site on the enzyme is available for another substrate to bind • An enzyme can function as a catalyst many, many times

14. Topic 3.6 – Enzymes • Identify the three factors that can effect enzyme activity. • Temperature • pH • Substrate concentration

15. Topic 3.6 – Enzymes • Identify the two factors that can cause an enzyme to denature. • pH • Temperature

16. Topic 3.6 – Enzymes • Draw a graph showing the effects of temperature on enzyme activity. Be sure to include proper axis labels. Explain the effects of temperature on enzyme activity. • Graph: bell curve; increasing temp. on x-axis, rate of reaction on y-axis • At lower temperatures, molecules move slower  less collisions between enzyme and substrate • As temperature increases, molecular movement increases  more collisions • Peak of bell curve = optimal temperature • After optimal temperature = denaturation

17. Topic 3.6 – Enzymes • Draw a graph showing the effects of pH on enzyme activity. Be sure to include proper axis labels. Explain the effects of pH on enzyme activity. • Graph: bell curve; pH on x-axis, rate of reaction on y-axis • Too acidic = large number of hydrogen ions (H+) can bond to negative charges of the enzyme or substrate • Too basic = large number of hydroxide ions (OH-) can bond to positive charges of the enzyme or substrate • In either case, bonding between the enzyme and substrate is disrupted • Enzyme becomes less efficient, possibly inactive in extreme situations (denatured)

18. Topic 3.6 – Enzymes • True or false: All enzymes work best at the same pH level • False – some prefer acidic environments (think pepsin in your stomach); some prefer neutral (think amylase in your mouth)

19. Topic 3.6 – Enzymes • Draw a graph showing the effects of substrate concentration on enzyme activity. Be sure to include proper axis labels. Explain the effects of substrate concentration on enzyme activity. • Graph: linear increase in the beginning, followed by a plateau; x axis: increasing substrate concentration; y-axis: rate of reaction • As substrate concentration increases, so does rate of reaction because your have more substrate • There is a limit; as substrate out-numbers enzyme, the rate of reaction slows down because every enzyme molecule is working as fast as possible, so adding more substrate will not increase the reaction rate

20. Topic 3.6 – Enzymes • When comparing/discussing data, what are important features you should include in your response? • Specific data • Trends in data • Units • Objective terminology

21. Topic 3.6 – Enzymes • In the lab you just completed, identify: the enzyme used and the substrate. • Pectinase • Pectin

22. Topic 3.6 – Enzymes • Maltose, a disaccharide, is a sugar used in the confectionary and brewing industries. Predict the name of the enzyme that breaks down maltose. • Maltase

23. Topic 3.6 – Enzymes • Just to recap … • If you haven’t figured it out yet, your quarter 1 exam covers IB topic 3.6 (enzymes) • Reflects papers 1 and 2 • 7 multiple choice • 1 short answer • 1 DBQ