1. Enzymes
Biochemistry

2. What You Need to Know!
Enzymes work by lowering the energy of activation.
The catalytic cycle of an enzyme that results in the production of a final product.
The factors that influence the efficiency of enzymes.

3. Special Proteins: Enzyme
Enzymes are proteins that speed up the rate of a chemical Rx
Making/breaking covalent bonds in cells
Also called a biological catalyst
Suffix: -ase
Enzyme
Substrate(s)  product(s)

4. Enzymes are large 3-D proteins that have a groove where they bind the substrate(s)  active site

5. Enzyme
Each enzyme:
Has a specific 3-D structure (due to the number and order of AA)
Can interact only with one type of substrate that fits in the active site: Lock and Key model

6. Catalytic Cycle Enzyme finds substrate
Substrate binds to active site “enzyme-substrate complex”

7. Enzyme Rx
Enzyme transforms the substrate into product “enzyme product complex”
Enzyme releases product
An enzyme can carry out a chemical Rx over and over again
it is not used up in the Rx
Substrates are used up

8. Activation Energy
Transformation from reactants to products requires the input of energy = activation energy
Enzymes can speed up a Rx because they lower the activation energy of the Rx

9. Enzyme Rx Rates Depend On:
Substrate concentrations
The more substrate, the faster the rate
Until present enzymes reach capacity
Enzyme concentrations
The more enzymes the faster the rate
Until substrate concentration becomes limiting factor pH
Can slow the rate due to denaturation of enzyme

10. Enzyme Rx Rates Depend On:
Temperature
Can slow rate due to denaturation of enzyme
Presence of inhibitors
Can slow down or block enzymes

11. To be continued…

12. Factors that affect enzyme activity:pH
Enzyme pepsin in stomach does not become active until it is in an acidic pH
Temperature
Each enzyme has an optimal temperature range
Cofactors or coenzymes
Bind to the enzyme to make it functional
Ex: metals such as Zn, Fe, Co, and vitamins
Inhibitors

13. 1. Competitive Inhibitor (reversible)
Mimics substrate molecule(s) (flat toothpicks) but cannot be metabolized
slows down Rx rate

14. 2. Non-competitive/allosteric inhibitors (reversible)
Molecules that do not bind to active site but at the allosteric (other) site
leading to conformation (change in shape)
Can turn off active site

15. Enzymes

16. 3. Non-competitive inhibitors-(irreversible)
Toxins
Poisons

17. Enzyme Regulation
Chemical chaos would result if all metabolic pathways in the body work simultaneously
Regulation through:
Transcription/translation
Active regulation of enzymes already made:
Allosteric Regulation
Feedback Inhibition

18. Active Regulation Allosteric Regulation: Feedback Inhibition:
Reversible non-competitive inhibitors or activators that the body makes
binds to allosteric site
Feedback Inhibition:
In long metaboloic pathways final products becomes allosteric inhibitors to the first enzyme