1. Enzymes and Chemical Reactions
Chapter 4 & 5

2. Chemical Reactions
During a chemical reaction, the atoms in the reactants get rearranged to form products
This requires bonds to break and reform…
The breaking and forming bonds involve changes in ENERGY!!

3. Energy in Reactions
Breaking bonds absorbs energy from the surroundings, but chemical energy is released
Forming bonds releases energy to the surroundings, but chemical energy is stored
Chemical reactions either absorb more energy than they release, or vice versa

4. Energy-Releasing Reactions
Often called Exothermic Reactions
Often occur spontaneously, or with little activation energy (energy needed to start the reaction)

5. Energy–Absorbing Reactions
Often called Endothermic Reactions
Require an energy source

6. Which is Which??

7. Enzymes are Catalysts
They speed up chemical reactions by lowering the activation energy
They speed up reactions in cells at normal body temperatures

8. Enzyme Structure Enzymes are made up of folded… PROTEIN!!
The folds created in the forth level of organization create ACTIVE SITES for SUBSTRATES to bind to
An enzyme can only catalyze ONE reaction (lock & key)

9. How Enzymes Work (Fig 5-13 p.104)

10. Enzyme Function
An enzyme’s structure and shape is critical to its function in the cell
High temperatures, changes to the pH, or some environmental factors can DENATURE protein (or unravel it)
No folds = No active sites
This is why it is important for living things to maintain homeostasis