1.  A catalyst  Is a chemical agent that speeds up a reaction without being consumed by the reaction  An enzyme is an organic catalyst  Enzymes are proteins

2. Enzyme Substrate (Reactants) Allosteric Site Active Site Activator or Inhibitor

3.  Enzymes can only work with certain substrates  The shape of the enzyme must match the shape of its substrate - The root of the enzyme’s name typically indicates the substrate which it acts upon e.g. ATPase, Amylase, Sucrase

4.  When the substrate binds to the active site, the enzyme changes conformation (shape) to make a better fit. Figure 8.16 (b) Enzyme- substrate complex Figure 8.16 Substate Active site Enzyme (a)

5. Sucrase Sucrose + Sucrase  Glucose + Fructose + Sucrase http://www.youtube.com/watch?v=eMuyKN _VW3k

6. The initial amount of energy needed to start a chemical reaction  The energy required to get the reactants ready to react Free energy Progress of the reaction EAEA Figure 8.14 A B C D Reactants A C D B Transition state A B CD Products activation energy  E A

7.  Enzymes lower the activation energy  How?  Orienting substrates correctly  Putting stress on substrate bonds  Providing a favorable environment  This increases the rate of the reaction. Progress of the reaction Products Course of reaction without enzyme Reactants Course of reaction with enzyme EAEA without enzyme E A with enzyme is lower Free energy Figure 8.15 http://www.youtube.com/watch?v=Dd1yi2a VoOc

8. (1) Increase the number of substrate molecules in solution (increase conc’n) (2) Increase the number of enzymes in solution (increase conc’n) (3) Increase the temperature of the solution (up to a certain point)

9.  A reaction is said to be “saturated” when 100% of enzymes have their active sites filled with substrate.  Vmax is maximum velocity (speed) of rxn

10.  If there are left-over reactants (substrates), then you could add more enzymes.  If there are no more left- over reactants (substrates), then adding more enzymes will not increase the rate.

11.  Change the pH so it is above or below its optimal value.  This changes the enzyme’s conformation (shape) causing it to become dysfunctional  E.g. Add H 2 SO 4(aq) (Sulfuric Acid)

12.  Above a certain temperature, enzymes’ activity starts to decline because the enzyme begins to denature (unravel)

13.  Reactions occur in a sequence and specific enzymes catalyze each step

14. Z U V W X Y (a)Z + Y  U U  V  W W  X + Y (b) Initial Reactant: Z End product: E (desired product)

15. Figure 8.19 (b) Competitive inhibition A competitive inhibitor mimics the substrate, competing for the active site. Competitive inhibitor A substrate can bind normally to the active site of an enzyme. Substrate Active site Enzyme (a) Normal binding Figure 8.19 A noncompetitive inhibitor binds to the enzyme away from the active site, altering the conformation of the enzyme so that its active site no longer functions. Noncompetitive inhibitor (c) Noncompetitive inhibition

16.  When one activator or inhibitor bind to an allosteric site, it will have an effect on all the subunits of an enzyme Stabilized inactive form Allosteric activater stabilizes active from Allosteric enyzme with four subunits Active site (one of four) Regulatory site (one of four) Active form Activator Stabilized active form Allosteric activater stabilizes active form Inhibitor Inactive form Non- functional active site (a) Allosteric activators and inhibitors. In the cell, activators and inhibitors dissociate when at low concentrations. The enzyme can then oscillate again. Oscillation Figure 8.20 http://www.youtube.com/watch?v=d5fDEU hjo-M

17. The end product of a metabolic pathway shuts down the pathway Active site available Isoleucine used up by cell Feedback inhibition Isoleucine binds to allosteric site Active site of enzyme 1 no longer binds threonine; pathway is switched off Initial substrate (threonine) Threonine in active site Enzyme 1 (threonine deaminase) Intermediate A Intermediate B Intermediate C Intermediate D Enzyme 2 Enzyme 3 Enzyme 4 Enzyme 5 End product (isoleucine) Figure 8.21 http://www.youtube.com/watch?v=c8FcZVJ S1Q8