1. Chapter 2-4
Chemical Reactions
and
Enzymes

2. Chemical Reactions Bonds break and form during chemical reactions.
Chemical reactions change substances into different ones by breaking and forming chemical bonds.
Na + Cl----> NaCl
Reactants
products

3. Reactants are changed during a chemical reaction
Products are made by a chemical reactions
Identify the products and reactants in the chemical reaction. Record on your paper.
MgO + CaS------> MgS + CaO

4. Energy in Reactions
Bond energy is the amount of energy that breaks a bond between two atoms.
Energy is absorbed to break bonds.
Energy is released when bonds form. Often in the form of heat, light and sound.
Some reactions occur fast, some very slow.

5. Equilibrium
A reaction is at equilibrium when reactants and product from at the same rate.
In order to stay alive, organisms need to carry out reactions that require energy.
While breathing, this reaction occurs in the blood through the lungs:
CO2 + H2O H2CO3

6. Activation Energy All chemical reactions release or absorb energy.
Activation energy is the energy needed to start a chemical reaction.

7. Releases more energy than it absorbs
Excess energy is given off as heat or light by the reaction
Reactants have higher
energies than the products

8. Endothermic Reaction Graph
Absorbs more energy than they release.
Energy is absorbed by the reaction.
Reactants have lower energy than products

9. Catalysts A catalyst lowers activation energy.
Catalysts are substances that start and speed up chemical reactions.
They decrease the activation energy and increase the reaction rate.

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

12. How Enzymes Work
Disruptions in temperature and pH can affect the structure and shape which prevents enzymes from functioning.
Enzymes function best in a small temperature range of conditions.
Changes in temperature and pH can break down the bonds in an enzyme.
An enzyme’s function also depends on its structure/shape.

13. An enzyme’s structure allows only certain reactants to bind to the enzyme. These reactants are called substrates.

14. Amylase is an enzyme found in saliva that breaks down starch into simple sugars.
Amylase is the enzyme and starch is the substrate.
Substrates fit perfectly like a lock into a key to illustrate how enzymes function.

15. Lock and Key Model

16. Substrates are brought together and the bonds in the substrate are weakened.
If an enzyme’s structure changes, it may not work at all.