1. Unit H: Enzymes

2. Standards Unit H: Enzymes
I can relate the function of thyroxin to metabolism.
I can use words and models to show the lock and key function of enzymes.
I can describe how co-enzymes and co-factors assist enzymes.
I can explain how enzymes help our metabolic reactions to occur
I can model/show how thyroxin production is regulated.
I can relate protein structure to the denaturation of enzymes and provide examples of conditions that cause denaturation.
I can represent the rate of enzyme activity graphically.

3. Energy & Cells Chemical reactions either store or release energy
Endergonic reactions absorb energy and yield products rich in potential energy
Energy & Cells
Potential energy of molecules
Reactants
Energy required
Products
Amount of energy required

4. Exergonic reactions release energy and yield products that contain less potential energy than their reactants
Cells carry out thousands of chemical reactions the sum of which constitutes cellular metabolism
Energy coupling uses exergonic reactions to fuel endergonic reactions
Reactants
Energy released
Products
Amount of energy released
Potential energy of molecules

5. ATP shuttles chemical energy and drives cellular work
ATP powers nearly all forms of cellular work
The energy in an ATP molecule lies in the bonds between its phosphate groups
Phosphate groups
ATP
Energy P
Hydrolysis
Adenine
Ribose
H2O
Adenosine diphosphate
Adenosine Triphosphate +
ADP

6. ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to make molecules more reactive
ATP
Chemical work
Mechanical work
Transport work P
Molecule formed
Protein moved
Solute transported
ADP +
Product
Reactants
Motor protein
Membrane protein
Solute

7. Cellular work can be sustained because ATP is a renewable resource that cells regenerate
ADP + P
Energy for endergonic reactions
Energy from exergonic reactions
Phosphorylation
Hydrolysis

8. Chloroplasts and mitochondria make energy available for cellular work
Enzymes are central to the processes that make energy available to the cell
Chloroplasts carry out photosynthesis using solar energy to produce glucose and oxygen from carbon dioxide and water
Mitochondria consume oxygen in cellular respiration using the energy stored in glucose to make ATP

9. HOW ENZYMES FUNCTION
Enzymes speed up the cell’s chemical reactions by lowering energy barriers
For a chemical reaction to begin reactants must absorb some energy, called the energy of activation
EA barrier
Reactants
Products 1 2
Enzyme

10. Progress of the reaction
A protein catalyst called an enzyme can decrease the energy of activation needed to begin a reaction
Reactants
EA without enzyme
EA with enzyme
Net change in energy
Products
Energy
Progress of the reaction

11. A specific enzyme catalyzes each cellular reaction
Enzymes have unique three-dimensional shapes that determine which chemical reactions occur in a cell
The catalytic cycle of an enzyme
Enzyme (sucrase)
Glucose
Fructose
Active site
Substrate (sucrose)
H2O 1
Enzyme available with empty active site 2
Substrate binds to enzyme with induced fit 4
Products are released 3
Substrate is converted to products

12. The cellular environment affects enzyme activity
Temperature, salt concentration, and pH influence enzyme activity
Some enzymes require non-protein cofactors such as metal ions or organic molecules called coenzymes

13. Normal binding of substrate
Enzyme inhibitors block enzyme action
Inhibitors interfere with an enzyme’s activity
A competitive inhibitor takes the place of a substrate in the active site
A noncompetitive inhibitor alters an enzyme’s function by changing its shape
Substrate
Enzyme
Active site
Normal binding of substrate
Enzyme inhibition
Noncompetitive inhibitor
Competitive inhibitor

14. Bozeman: Enzymes

15. CONNECTION Many poisons, pesticides, and drugs are enzyme inhibitors
EX: Cyanide is a inhibitor in the cellular respiration reaction in the mitochondria. It causes a build-up of O2 in the blood and ultimately results in suffocation

16. Thyroid Gland
Thyroid gland produces thyroxine (T4 & T3), a hormone used to regulate metabolism in our bodies
Metabolism is the total work done by all the cells in our bodies
Most of the work in our bodies is done by enzymes
Increasing thyroxine levels increases enzyme activity, decreasing thyroxine levels decreases enzyme activity
Hyperthyroidism: over active thyroid gland; more thyroxine produced (greater enzyme activity and more energy used)
Hypothyroidism: under functioning thyroid gland; less thyroxine produced (lower enzyme activity and less energy used)

17. TED ED

18. Thyroid Problems