Biological Reactions regulated by Enzymes Flashcards
Enzymes are…
Proteins
“Biological catalysts”
Enzymes reduce…
Activation energy
Catabolic reaction
Enzymes break things down
Anabolic reaction
Enzymes build things up
Metabolism
Series of enzyme reactions (catabolic and anabolic)
Lock and key hypothesis
Enzyme = lock, active site = key hole, substrate = key
Substrate shape is complimentary to fit active site shape, successful collision between substrate and enzyme’s active site results in enzyme-substrate complex
Induced fit hypothesis
Active site shape will change for substrate to fit
E.g Lysozyme (breaks down bacterial cell walls)
Enzymes - temperature
As temp increases, rate of reaction increases. Once optimum temp is exceeded, enzyme denatures
Enzyme is a protein
Has a tertiary structure - 3D globular structure held by disulphide bonds
Factors that affect enzymes
Temperature, pH, enzyme concentration, substrate concentration
Enzymes - pH
Small changes from optimum in pH causes inactivation (enzyme doesn’t work as well because H bonds disrupted)
Enzymes - substrate concentration
Increasing concentration doesn’t affect reaction rate once point of saturation is reached
Increased concentration increased likelihood of successful collisions
Enzyme - enzyme concentration
Increased enzyme concentration, increased rate (until all substrates saturated) - rate keep increasing if substrate in excess
Enzyme inhibition
Inhibitors slow down enzyme rates of reaction/stop enzymes working completely
Reversible reaction
Can be reversed, enzymes can function properly again
Types of reversible reactions
Competitive and non-competitive
Competitive e.g. Malonic acid
Competition for active site from substrate and inhibitor
Inhibitor blocks active site so no reaction can take place, when it leaves, active site is free to function
Non-competitive e.g. Cyanide
Bonds with enzyme anywhere but active site
Inhibitor changes shape of active site
Irreversible reaction
Enzyme destroyed and stopped from working e.g. Heavy metals
Immobilised enzyme
Fixed in place (can’t move!)
Advantages to using immobilised enzymes
- economically viable, enzymes reused easily
- easier to separate product at end
- easier to control rate of reaction
- enzyme less likely to denature (can use higher temperatures for faster rate)
- use a mixture of enzymes that wouldn’t normally work together
Examples where immobilised enzymes are used in industry and medicine
To make lactose free milk
To make a ‘biosensor’ for blood/glucose or glucose oxidase
How does a biosensor work?
Uses enzymes to detect specific molecules at low concentrations
