1. Enzymes
Organic Catalysts

2. Chemical Reactions
Every chemical reaction between molecules involves bonds breaking and bonds forming.
Changing one molecule into another generally involves contorting the starting molecule into a highly unstable state before the reaction can proceed.
To reach this state, reactant molecules must absorb energy from their surroundings.
When new bonds are formed, energy is released as heat and the molecules return to a stable conditions with lower energy.

3. The Energy Profile of an Exergonic Reaction for a hypothetical reaction
AB + CD AC + BD
To each rthis state
EA = activation energy

4. Enzymes Enzymes are organic catalysts.
Involved in chemical reactions but not altered by them.
Many enzymes function by lowering the activation energy.

5. Enzymes decreases EA
Without enzyme:
With enzyme:

6. Most enzymes are protein molecules with a specific 3-dimensional shape
Active site
substrate
There are over 5000 enzymes known to exist, each of which is specific to a different reaction. Nearly every chemical process that takes place in living organisms is facilitated by an enzyme.
enzyme
“induced fit”

7. Enzymes catalyze reactions in living organisms:. 1
Enzymes catalyze reactions in living organisms: Bring reactant molecules close together 2. Make bonds easier to break/form
Induced Fit Model

8. Enzyme (Lock & Key Model)
Enzymes bind temporarily to one or more of the reactants — the substrate(s) — of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction.

9. How Enzymes Work
Enzymes lower the activation Energy (EA) by weakening bonds in the substrate molecule
energy +

10. Factors that affect enzyme activity
The activity of enzymes is strongly affected by changes in pH
Temperature
Concentration of Enzyme
Concentration of Substrate
Each enzyme works best at a certain temperature and pH, its activity decreasing at values above and below that point.

11. Figure 6.16 Environmental factors affecting enzyme activity