1. Section 2-4 & 2-5 “Chemical Reactions & Enzymes”
Write everything that is BLACK

2. California State Standards
The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:
Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings

3. Section 2-4 KEY CONCEPT: Life depends on chemical reactions.

4. Learning Objectives:
Students will be able to:
Describe how bonds break and reform during chemical reactions.
Explain why chemical reactions release or absorb energy.

5. Bonds break and form during chemical reactions
Chemical reactions change substances into different ones by breaking and forming chemical bonds
+ O2
CO2 + H2O

6. Products are made by a chemical reaction
Reactants are changed during a chemical reaction (the starting chemicals)
Products are made by a chemical reaction
Chemical Reaction
Reactants
Products

7. form carbon dioxide and water.
Quick Practice
Label the chemical equation below:
Reactants
Chemical Reaction
Products
The process of cellular respiration requires that bonds be broken and new bonds formed.
Oxygen and sugar will
form carbon dioxide and water.
Chemical Reaction
6 O2 + C6H12O6
6 CO H2O
Reactants
Products

8. Energy is added to break bonds. Energy is released when bonds form.
Bond energy is the amount of energy that breaks a bond between two atoms.
Bonds between different types of atoms have different bond energies – for example: water and glucose
Energy is added to break bonds.
Energy is released when bonds form.
Amount of energy to form and break the same bond is the same: example water molecule

9. CO2 + H2O H2CO3 Chemical Equilibrium
Many reactions in living things are reversible – they move in both directions at the same time.
CO2 + H2O H2CO3
When carbon dioxide concentration is high, as it is around your cells, the reaction moves to the right and carbonic acid is formed. In your lungs carbon dioxide concentration is low, so carbonic acid breaks down to form carbon dioxide and water
A reaction is at equilibrium when the reactants and products are being formed at the same rate.

10. Chemical reactions release or absorb energy.
Activation energy is the amount of energy that reactants need to absorb to start a chemical reaction

11. Exothermic reactions release energy
The products of a chemical reaction have lower bond energy than the reactants.

12. Endothermic reactions absorb (use) energy
The products of a chemical reaction have higher bond energy than the reactants.

13. Review Objectives – write these down and answer them
Describe how bonds break and reform during chemical reactions.
Explain why chemical reactions release or absorb energy.

14. Describe how bonds break and reform during chemical reactions.
Energy is added to break the bonds in the reactants then energy is released when new bonds form between atoms
Explain why chemical reactions release or absorb energy.
It depends on the bond energy (energy needed to break bonds between certain atoms)

15. Chemical Equilibrium
Some reactions go from reactants to products until all the reactants are used up. Other reactions are reversible. Many reactions in living things can move from reactants to products and back and forth.
Equilibrium – “balanced” think pulling on a rope each pull opposite directions but at an equal rate- forces are being exerted
Example ; Blood carries carbon dioxide waste from cells to lungs because of the reaction:
CO2 + H2O H2CO3

16. Chemical Equilibrium is reached when both reactants and products reach the same rate
Why is concentration important in a chemical reaction?
Concentration can alter the equilibrium of a chemical reaction. A higher concentration of reactants means more reactants can be reacting so pushes the reaction to making more products

17. Write everything that is BLACK
Section 2-5 “Enzymes”
Write everything that is BLACK
Essential Question: How are enzymes and macromolecules essential for life?

18. Today’s Objectives – write these down
Explain the effect of a catalyst on activation energy.
Skip a line (to answer this later)
Describe how enzymes regulate chemical reactions.
Skip 2 lines (to answer this later)

19. Section 2-5 KEY CONCEPT: Enzymes are catalysts for chemical reactions in living things.

20. Catalysts are substances that speed up chemical reactions
lowers activation energy
increase reaction rate

21. Enzymes are catalysts in living things.
Enzymes are needed for almost all processes
Most enzymes are proteins.

22. Disruptions in homeostasis can prevent enzymes from functioning.
Enzymes function best in a small range of conditions.
Changes in temperature and pH can break hydrogen bonds.
An enzyme’s function depends on its structure.

23. Substrates bind to an enzyme on its active sites
An enzyme’s structure allows only certain reactants to bind to the enzyme.
substrates (reactants)
enzyme
Substrates bind to an enzyme on its active sites

24. The lock-and-key model helps illustrate how enzymes function
substrates brought together
bonds in substrates weakened
Substrates bind to an enzyme at certain places called active sites.
The enzyme brings substrates together and weakens their bonds.
The catalyzed reaction forms a product that is released from the enzyme.

25. Describe how the interaction between an enzyme and its substrate changes a chemical reaction?

26. Describe how the interaction between an enzyme and its substrate changes a chemical reaction?
An enzyme brings substrates close together so they can react and slightly weaken the bonds within the substrate by changing the shape of the molecule

27. How does the structure of an enzyme affect its function?
Check
How does the structure of an enzyme affect its function?
Answer: If the structure of the enzyme changes, its function will change

28. Review Today’s Objectives
Explain the effect of a catalyst on activation energy.
Describe how enzymes regulate chemical reactions.

29. Review Today’s Objectives
Explain the effect of a catalyst on activation energy.
Answer
Catalysts speed up chemical reactions by
lowers activation energy
increase reaction rate

30. Review Today’s Objectives
Describe how enzymes regulate chemical reactions.
Answer:
Enzymes bring together substrates and weakens the chemical bonds enabling the reaction to occur. The catalyzed reaction forms a product that is released from the enzyme.