1. Enzymes
They’re terrific, they’re specific, without them life would be horrific!
Shape, Function, Action!

2. Enzymes Special proteins
Control the rate of chemical reactions that are needed for metabolism and homeostasis
Also called catalysts
Not used up or changed at all during the chemical reaction – only affect the rate of the reaction

3. Enzyme names Almost all enzymes end in the letters –ase
Named after their substrate: the substance that they act upon
Example: the enzyme that works on lipids is called lipase
Now you try:
1) Maltose: _________________
2) Sucrose: _________________
3) Lactose: _________________
4) Proteins: _________________

4. Enzyme Characteristics
Often large and complex proteins
Some contain a non-protein component called a co-enzyme
Some enzymes need their co-enzymes and will not function without them
Vitamins are often co-enzymes

5. Enzyme Shape
Made of polypeptide chains that are folded in a specific way
The folds form pockets on the surface of the enzyme
These three-dimensional pockets fit the substrate exactly
The spot where the enzyme and substrate come together is called the active site
When they are bonded together, they are called an enzyme-substrate complex

7.                                                                                                           
The image shows a substrate based inhibitor in the GT region (blue) of the PBP2 enzyme that blocks bacterial cell wall synthesis. The GT region of the PBP2 enzyme is responsible for creating a sugar chain from the individual lipid II molecules. Illustration: Courtesy of Natalie Strynadka

8. Lock and Key Model The enzyme’s active site has a unique 3-D shape
The enzyme and substrate form a complex when they bond together
The substrate fits the active site like a key fits a lock
In many cases a substrate will be broken into two products by an enzyme

9. Water is added to split this sugar. What is this process called?
What is another word for catalyst?
What do you notice about the end products?

10. Factors Influencing Enzyme Action
Temperature
Enzyme / Substrate concentrations pH

11. Temperature on Enzyme Action
Affects the rate of the reaction
Up to a point, as temperature increases so does the rate of the reaction
Optimum temperature: the temperature at which the enzyme works best
Above this temperature, enzyme function decreases
Denaturation: when the 3-D shape of the enzyme is warped at the active site
It basically melts
It no longer fits the substrate (so the reaction won’t occur)

12. Temperature on Enzyme Action
In humans, normal body temperature is: 37 degrees Celsius
So, the optimum temperature for most human enzymes is: 37 degrees Celsius
Denaturation begins at 40 degrees

13. Enzyme / Substrate Concentrations
High enzymes with low substrate = slow rate of reaction
If the concentration of substrate increases, the rate of reaction increases
When everyone is in the game, the rate levels off

14. pH pH scale measures H+ ion concentration Goes from 0 – 14
Below 7: Acidic
Above 7: Basic
7 is Neutral
Optimum pH: the level at which an enzyme works best at

15. pH
Blood is neutral (pH of 7), so most enzymes in the blood work best at a pH of 7
The stomach is very acidic. Pepsin (a digestive stomach enzyme) works best at a pH of 2
The small intestine is basic. Trypsin (an enzyme in the small intestine) works best at a pH of 8.