What are Enzymes
Proteins that are involved in all metabolic reactions, where they function as biological catalysts
What is a catalyst
A substance that increases the rate of a chemical reaction and is not changed by the reaction
Enzymes
- Made up of amino acids that join together in a long chain and fold in a specific way.
- Unique enzyme shape is specific to catalyse one particular metabollic reaction
The 3 main reactions catalysed by enzymes
- breaking large molecules into smaller ones
- converting one small molecule into another
- building up large molecules from small ones
Breaking large molecules into smaller ones
- Digestion
- The nutrients we eat are large and insoluble, we have to break them down into small soluble molecules to be absorbed into the blood in the small intestine
Converting one small molecule into another:
Adding or removing groups of atoms
Building up large molecules from small ones:
- eg: glucose joined together
- storage molecules eg starch/glycogen inside cells
- or structural molecules eg: cellulose
Describe enzyme action
1) enzyme has a unique shape, shape of the active site is complementary to the shape of the substance
2) substrate binds to the enzymes active site to form an enzyme substrate complex
3) enzyme releases the products. It is not used up in the reaction so it is now fine to catalyse another reactiom
Which 2 factors affect the rate of enzymes?
pH and temperature
Effect of temperature on enzyme activity
When the temperature increases the enzyme activity increases as there is more kinetic energy therefore there are more succseful collisions
What is denaturing
+The shape of the active site is changed
- The enzyme active site is mantained by bonds -> at very high temperatures, the bonds in the active site of an enzyme are broken and therefore the active site changes shape
- Active site is no longer complimentary to the substrate molecules -> enzyme won’t work again
Effect of pH on enzymes
As the pH increases, so does the enzyme activity until it reaches its optimum pH, from then the enzyme activity decreases as the bonds are broken and enzyme becomes denatured
Amylase
A carbohydrase enzyme that breaks down starch to glucose in the mouth and the small intestine
Function of hydrochloric acid in gastric juices
- kills harmful microorganisms in food
- It is acidic so the enzyme activity of pepsin is able to work in the stomach
Bile
It is produced in the liver and emulsifies fat therefore increases the surface area
