1. Enzymes and Metabolism

2. Metabolism The sum of all rxns that occur within a cell
Rxns either require or produce ATP
Rxns that occur within a cell are regulated by the production of specific enzymes (proteins coded by DNA)

3. A  B  C  D Metabolic Pathway
Series of linked rxns, requiring many enzymes
A  B  C  D
Enzyme 1
Enzyme 2
Enzyme 3
Substrate
Product
Product
Product
Substrate
Substrate

4. Thyroid Gland Produces thyroxin (hormone) that functions to:
Increase metabolic rate
Stimulate all cells (no target organ)
Stimulate production of enzyme that breaks down glucose and release NRG
More glucose is broken down
More NRG is utilized
Increase O2 consumption
Increase heart rate

5. Cellular Respiration Glucose + O2  CO2 + H2O + ATP
Glucose breakdown is exergonic as it creates ATP for use within cells

6. Characteristics of Enzymes
Enzyme combine briefly with substrate during rxn
Enzymes are released unchanged
Enzymes are specific
Enzymes are saturated by high [substrate]
Enzymes are pH and temperature sensitive

7. Characteristics of Enzyme con’t
6. Enzymes contain protein & non-protein groups called:
Substrate
Cofactor/coenzyme (non-protein part)
Apoenzyme (protein part)
Active Site – area on enzyme where substrate binds on to

8. Enzyme Inhibition

9. Competitive Inhibiton
Uncreative molecule that resembles the substrate combines with active site of enzyme
Block access of normal substrate so rxn rate slows down

10. Non-competitive Inhibitors
Inhibitors that bind to enzyme outside of active site (ex. Poisons, toxins)
AKA: Allosteric Inhibitors – bind to site other than active site, resulting in a shape change of enzyme  enzyme = no function
Changed the shape of active site
Substrate
Active site
Allosteric inhibitor
Allosteric site
enzyme

11. How is homeostasis maintained?
How do cells control the level of activity of enzymes within the cell?

12. Feedback Inhibition (Negative Feedback) Competitive Inhibition
When product is in abundance in cell, it binds to the active site of the enzyme, competing for space with the substrate. Rxn rate decreases.
Non-permanent binding – when the [product] is lowered, the product leaves active site to allow more substrate to bind. In this way, the [product] stays within a certain range

13. Feedback Inhibition (Negative Feedback) Non-Competitive Inhibition
Within metabolic pathway, the end product can also bind to an allosteric site of the first enzyme in the pathway. This binding causes a change in the enzyme's shape and it can no longer function, decreasing the rxn rate
D Binds to E1 therefore entire rxn stops
A  B  C D
Internet Video E1 E2 E3

14. Enzyme Review
Enzyme Song

15. Provincial Questions
What is structure Y? A. a product B. a reactant C. an active site D. an enzyme-substrate complex

16. Competitive inhibitors bind to which structure? A. W B. X C. Y D. Z

17. The changes shown in the diagram cause the rate of an enzyme-catalyzed reaction to decrease because A. the enzyme denatures the substrate. B. the substrate cannot bind to the active site. C. the coenzyme is unable to bind to the substrate. D. the enzyme can no longer increase the activation energy.

18. Which of the following describes the function of an enzyme. A
Which of the following describes the function of an enzyme? A. It speeds up a chemical reaction. B. It increases the available substrate. C. It increases the activation energy of a reaction. D. It contributes atoms to facilitate a chemical reaction.