1. Please Take out the Following
Pencil
Science Journal
Agendas
Macromolecules Worksheet (Pass it forward if you have not done so already).
Plan for the week

2. Science Question of the Day
Explain why the chemical bonds in the body do not break down, spontaneously, releasing all of their energy.

3. 5.3 Chemical Reactions
Chemical reactions begin with reactants (substrates) which are converted to products
Exergonic reactions
Products contain less energy than the reactants
Endergonic reactions
Products contain more energy than the reactants

4. Fig. 5.4
Energy of Activation
Extra energy required to destabilize chemical bonds and so initiate a chemical reaction

5. However, they cannot make an endergonic reaction exergonic
Fig. 5.4
Catalysts lower the activation energy of a reaction, and thus increase its rate
However, they cannot make an endergonic reaction exergonic

6. 5.4 How Enzymes Work Enzymes are proteins that serve as catalysts
They speed up chemical reactions within cells
Enzymes bind a specific molecule and stress bonds to make a particular reaction more likely
Active site
Site on enzyme surface where reactant fits
Binding site
Site on reactant where enzyme binds
They give the reactants a nudge so that they can come over the activation energy. Pushing a boulder down a hill vs. digging the ground under the boulder.

7. Fig. 5.5 Enzyme shapes determines its activity
Lysozyme
Changes upon binding of the substrate
The substrate is now bound more intimately
Enzyme shifts shape and encloses the substrate like a glove on a hand.

8. Fig How enzymes work
Enzymes catalyze reactions by either bringing the molecules close to each other so that they can link up or by pressing on specific bonds to make them break easier.

9. Fig. 5.7 The catalytic cycle of an enzyme1
The substrate, sucrose, consists
of glucose and fructose bonded together.
Bond
Enzyme
Active site
Glucose
Fructose
Products are released, and the enzyme is free to bind other substrates. 4
The substrate binds to the enzyme, forming an enzyme-substrate complex. 2
H2O
The binding of the substrate and enzyme places stress on the glucose-fructose bond, and the bond breaks. 3
This is how they function to break bonds.

10. 5.5 Factors Affecting Enzyme Activity
Enzyme activity is affected by any change in condition that alters the enzyme’s 3-D shape
The structural bonds of enzymes are sensitive to changes in temperature and pH
Therefore, a temperature or pH beyond the optimal range will cause the enzyme to denature

11. Enzyme Activity

12. Fig. 5.8 Enzymes are sensitive to their environment
Digests proteins in the stomach
Digests proteins in the intestine
Each enzyme functions at a specific pH and Tempreture and if those are interrupted, the Enzyme, a protein, will denature.

13. 5.6 How Cells Regulate Enzymes
A cell can control the activity of an enzyme by altering its shape
Allosteric enzymes have shapes that can be altered by the binding of signal molecules
These molecules bind to the allosteric site
Repressors bind and repress enzyme activity
Activators bind and restore or increase enzyme activity

14. Fig. 5.9 How cells control enzymes

15. Enzyme inhibition occurs in two ways:
Competitive inhibition
- Inhibitor binds at the enzyme’s active site
Noncompetitive inhibition
- Inhibitor binds at the enzyme’s allosteric site
Fig. 5.10

16. Enzymes Reviewed