2.5 Enzymes Flashcards
Enzyme
a globular protein which acts as a biological catalyst by speeding up the rate of a chemical reaction
Active site
the region on the surface of the enzyme which binds to the substrate molecule
Where do enzyme reactions often occur?
aqueous solutions
Describe the process of enzyme catalysis
- a substrate binds to the enzyme’s active site forming the enzyme-substrate complex
- the enzyme catalyses the conversion of the substrate into a product, creating a enzyme-product complex
- the enzyme and product dissociate
- the enzyme then continues to catalyses further reactions
How to increase the frequency of collisions in enzyme catalysis?
increase the molecular motion of the particles (thermal energy to increase kinetic energy)
increase the concentration of particles
What modifies enzyme structure?
temperature
pH
How can an enzyme structure be affected?
high temperatures and extreme pH disrupt chemical bonds that maintain the tertiary structure of the enzyme
changes the active site (denaturation) can prevent the enzyme’s capacity to bind the substrate
What factors may affect rate of activity of enzymes?
temperature
pH
substrate concentration
How does temperature affect rate of enzyme activity?
low temperatures - insufficient thermal energy for the activation of an enzyme-catalysed reaction to preceed
higher temperatures - increase the speed and motion of both enzyme and substrate -> higher enzyme activity
optimal temp - highest rate of reaction
higher temperatures - enzyme’s hydrogen bonds are disrupted and thus denaturation
How does pH affect rate of enzyme activity?
charge of enzyme will be altered, which will alter protein solubility and overall shape
change the shape or charge of active site will diminish its ability to bind the substrate
optimal pH - moving outside of this will diminish enzyme activity
How does substrate concentration affect rate of enzyme activity?
more substrates = increased chance of enzyme and reacting within a given period
after a certain point, the rate of activity will cease to rise regardless of any further increases in substrate levels
What are the factors to test the effect of factors affecting enzyme activity?
which factor to investigate (temp/concentration/pH)
which enzyme/substrate to use
how to measure enzyme activity
What are independent variables that can be chosen from?
temperature
pH
substrate concentration
presence of inhibitor
Examples of common enzyme-catalysed reactions:
- catalase - hydrogen peroxide - oxygen + water
- pepsin - protein - short polypeptides
- diastase - starch - maltose
What are ways to measure enzyme activity?
gas production
digestion of a solid
digestion of a liquid
colour change
Ways to measure gas production
count bubbles
gas syringe with increasing volume of gas
pressure change in sealed environment (data logger)
Ways to measure digestion of a solid
calculate % weight change
change in diameter
volume of liquid produced
Ways to measure digestion of a liquid
diffusion out of dialysis tube
Ways to measure colour change
starch reacts with iodine (purple colour)
peptide bonds are stained via the Biuret test
reducing vs non reducing sugars
What are immobilised enzymes used for?
biofuels medicine biotechnology food production textiles paper
How is lactose-free milk produced?
the enzyme lactase is purified from yeast or bacteria and then bound to an inert substance
milk is then repeatedly passed over this immobilised enzyme, becoming lactose-free
What are some advantages of lactose-free dairy products?
a source of dairy for lactose-intolerant individuals
increase sweetness in the absence of artificial sweeteners
reduce crystallisation of ice creams
reducing production time for cheeses and yogurts
