| What is an enzyme? (5) | globular protein acts as a biological catalyst by speeding up the rate of a chemical reaction = Enzyme catalysis
Are not changed / consumed = reused
named after the molecule it reacts with (substrate)
ends with -ase
eg: lipids broken down by lipase |
| What is a substrate? | the molecules which enzymes react with |
| What is the active site on enzymes? (2) | region on the enzyme which binds to the substrate molecule with high specificity
shape and chemical properties depends on the tertiary structure of the enzyme |
| Why are there specific substrates for a particular enzyme's active site? | because the active site and the substrate complement each other in terms of shape and chemical properties |
| Where do enzyme reactions take place? | in aqueous solutions (eg: cytoplasm) |
| Describe the movement of enzyme reactions? (2 diff explan) | the substrate and enzyme move randomly within the solution (Brownian motion)
sometimes the enzyme can be fixed (membrane bound) to localize reactions to particular sites |
| What does enzyme catalysis require? (3) | substrate needs to be close to the active site to bind with it to form an enzyme-substrate complex
enzyme catalyses the conversion of substrate = produce = enzyme product complex
enzyme and product dissociates = enzyme continues catalysing reactions |
| What happens after enzyme catalysis? | enzyme and product dissociate - enzyme isn't consumed = continues to catalyse further reactions |
| How can the rate of enzyme catalysis be increased? (3) | by increasing the frequency of collisions by:
increasing the molecular motion of the particles
(by thermal energy = increased kinetic energy)
increasing the conc of particles (substrate/ enzyme) |
| What can denature enzymes? (3) | high temperatures and extreme pH
breaks the chemical bonds needed to maintain the tertiary structure of the enzyme
= denaturation decreases the enzymes ability to bind to the substrate |
| How does diff temperature affect enzyme activity? (4) | Low temp: not enough thermal E to activate an enzyme catalyzed reaction.
High temp: increases speed + motion of enzyme and substrate = higher enzyme activity bec of more frequent collisions
Optimal: enzyme activity at its peak
Too high Temp: enzyme stability decreases, thermal E disrupts the H bonds in enzyme = lose its shape = denaturation |
| How can different factors affect an enzyme's activity? (2) | affect frequency of enzyme-substrate collisions
denaturation = affects how well the enzyme and substrate interacts |
| How does pH affect enzyme activity? | changing pH changes the enzyme's charge = changes solubility and shape
changing shape / charge of active site reduces ability to bind to substrate |
| How does substrate conc affect enzyme activity? (2) | increasing conc increases activity bec higher chance of the enzyme and substrate colliding
after a certain point the activity rate will stop rising because the environment is saturated with substrate and all the enzymes are bound and reacting |
| What to include when testing for the effect of temp, pH and substrate conc on enzyme activity? | independent variable = temp (water baths) , pH (acidic/ alkaline solutions), substrate concentrations
Enzyme/ substrate being used = pepsin, protein - short polypeptides
How to measure enzyme activity = colour change (biuret's test) |
| What are immobilized enzymes? | They are fixed to a static surface to improve the efficiency of a catalyzed reaction
bec fixed = enzyme concs easily conserved
separation of the product is easier to achieve = higher yield |
| Where are immobilized enzymes used ( 3 examples) | Biofuels = enzymes are used to break down carbs = produces ethanol based fuels
Medicine = Enzymes used to identify diseases and pregnancy
Food production = Enzymes used in production + refinements of beers and dairy products |
| How is lactose free milk produced? | lactase is purified from yeast / bacteria and bound to an still substance (eg: alginate beads)
Milk is passed over the beads and becomes lactose free |
| What is lactose? | it is a disaccharide of glucose + galactose which can be broken down by the enzyme lactase |
| What are the advantages of lactose free milk? | source of dairy for lactose intolerant people
increasing sequence without artificial sweeteners (monosachs are sweeter)
reducing crystallization of ice creams (monosachs are more soluble = less likely to crystallize)
reducing production time for cheeses and yoghurts
(mono is fermented more easily) |
