5.5 Enzymes are proteins that speed up specific reactions in cells

1. Enzymes and Activation Energy
a. To start a chemical reaction, you need to weaken chemical bonds in the reactant molecules.
b. The activation process above requires the molecules to absorb energy.
c. Start-up energy is called the activation energy because it activates the reactants.
d. Hotter molecules may collide with enough energy to eaken bonds while cooler molecules collide with less energy
e. Cellular reaction depends on the cataylsts, which are compounds that speed up the chemical reaction. The main catalyst is proteins called enzymes.
f. Enzymes provide a way for reactions to occur at the cell's normal temperature.
- enzymes do not supply the activation energy, instead, it lowers the energy barriers so the reaction can speed up.
g. Each enzyme catalyzes a specific kind of chemical reaction.

2. How enzymes work
a. The shape of each enzyme fits the shape of only particular reactant molecules.
b.Subtrate is a specific reactant acted upon by an enzyme. The subtrate fits into a active site.
c. Active site changes shape when subtrate enters.
d.The tighter the grip, the subtrate will be weakened in its bonds.
e. Enzymes can lower activation energy by accpeting two reactant molecules into adjacent sites.

Concept Check:
1. Explain the role of activation energy ina reaction. How does the enzyme effect the activation energy?
- The activation energy activates the reactants and the enzymes can lower its energy barriers so that the reaction can speed up.
2. Describe how subrate interacts with an enzyme.
-Together, they lower the activation energy so that the reaction could proceed.