Enzymes & Metabolism
Metabolism
Metabolism is all the chemical reactions that occur within a living organism
All these reactions are controlled by enzymes
A metabolic pathway describes a series of reactions which result in a particular process e.g respiration
Metabolic reactions can be divided into anabolic and catabolic reactions
Enzymes
An enzyme is a protein that speeds up a chemical reaction without being used up in the reaction
Properties of Enzymes
- Made of protein
- Speed up chemical reactions
- Specific to one reaction
- Can be reused many times
- They have a specific region on their surface which is called the active site
- They work on a substrate
- They produce a product
- Sometimes they need a co-enzyme to work
Examples of Enzymes
| Enzyme | Definition |
|---|---|
| Pancreatic Amylase | Breaks down starch into glucose |
| Protease | Breaks down proteins and polypeptides into amino acids |
| Lipase | Breaks down fats into fatty acids and glycerol |
Mechanism of Enzyme Action - Induced Fit Theory
The active site of an enzyme is a specific shape to fit the substrate
When the active site comes in close contact with the substrate it changes shape to closely fit the substrate
When the enzyme and substrate are joined together, it is called the ‘enzyme-substrate complex’
The enzyme returns to its original shape and is then released leaving the product behind
The enzyme can now catalyse another reaction
Factors influencing enzyme activity
- pH
- pH is a measure of how acidic or alkaline (base that is soluble in water) a solution is
- Most enzymes work best in a narrow pH range close to neutral
- Outside this pH range the shape of the enzyme changes and it an no longer catalyse the reaction. BECOMES DENATURED
- Pepsin is an exception. It’s optimum pH is 2 because it is active in the stomach
Effects of pH on enzyme activity - Graph
- Temperature
- Temperature effects enzyme activity
- Low temperatures mean less activity
- As temperature increases, activity increases until it reaches an optimum temperature
- Above the optimum temperature, activity starts to decrease
- High temperatures changes the shape of an enzyme and it becomes inactive - denaturation
- Optimum temperature for human enzymes is 37°C - normal body temperature
- Optimum temperature for plant enzymes is 20 - 25 °C
Effects of temperature on enzyme activity - Graph
Biotechnology (Bioprocessing)
- Biotechnology = Using living organisms or their enzymes to make useful products
- Traditional
- Brewing - using yeast
- Baking - using yeast
- Cheesemaking - using bacteria or fungi
- Modern
- Antibiotics - using bacteria or fungi
- Insulin - using genetically modified bacteria
- Antibodies - to make diagnostic kits
Immobilised Enzymes
A modern technique
Useful enzymes (or a unicellular organism like yeast) are extracted
They are attached to an inanimate material (e.g. alginate) - immobilised
They are put into a column and the substrate poured on top
The product is collected at the end
Diagram of column containing immobilised enzymes
Advantages of Immobilisation
They can reused many times
They are easily separated from the product
They are more stable
Examples:
Converting sucrose to glucose by the enzyme invertase
Converting glucose to ethanol by yeast