Zusammenfassung der Ressource
Enzyme Action
- Enzymes
- Work intracellular, in the cell, and extracellular, outside the cell
- Lock and Key model
- substrate fits the active site like a key in a lock
- however its found that the enzyme substrate complex changed shape slightly
- 'Induced fit' a better theory
- substrate has to make the active site change its shape to fit specifically for the substrate
- Properties of enzymes structure
- Related to tertiary strcuture
- active site due to tertiary which itself is due to primary
- Each enzyme different
- Mutations of gene may change enzyme produced
- very specific, catalyses one reaction
- as one complementary substrate fits
- Factors Affecting Enzymes
- Temperature rises, causing molecules to vibrate more
- if temperature goes too high,
- Breaks some bonds within the enzyme so it loses shape
- Enzyme becomes denatured, loses function as an enzyme
- pH, most enzymes optimum at 7 pH
- Exceptions e.g. pepsin at pH 2
- ionic and H-bonds in tertiary structure can be altered by acids and akalis
- denatures enzymes
- Concentrations
- Increasing Enzyme Conc
- Increases the frequency of successful collisions to form substrate-enzyme complexes
- This increases the rate of reaction
- Up to a point that the substrate runs out if substrate limited
- Increases the rate up to the point of "saturation"
- Saturation is when all the active sites are full
- Therefore adding more substrate makes no difference
- Conc of substrate does decrease over time as products formed
- Rate also decreases if substrate is not added, initial rate is the highest
- Increasing Substrate Conc
- Inhibition
- Eznyme inhibitors prevent enzyme activity
- Molecules bind to enzyme to inhibit it
- Competitive
- Competitive inhibitors have similar shape to substrate
- Inihibtors and substrate compete to occupy active site
- If inhibitors occupy the active site no reaction takes place and the active site is blocked
- If there is high substrate conc, more chance for substrate to bind to active site
- Increases rate of reaction to a point
- Increase Inhibitor conc
- Inhibitors will occupy nearly all active sites leaving a very low rate of reaction
- Non-competitive
- Non-competitive inhibitor attach to binding sites, way from the active site
- Causes active site to change shape
- Substrate can no longer bind to active site
- Prevents enzyme from functioning
- Changing conc of substrate has no effect
- Enzyme Reactions
- Measuring the rate of enzyme-controlled reactions
- Measure how fast product is made
- Catalase breaks down hydrogen peroxide to form water and oxygen
- Measure how much oxygen produced
- Measure how fast substrate is broken down
- Biological Catalysts
- Catalysts for metabolic reactions
- Lower the Activation Energy of a Reaction
- If substrates are closer together, reduces repulsion easier to bond molecules together
- If breaking down molecule, attatching to active site puts pressure on molecules bonds
- Have active sites and specific shape
- Proteins
- Highly specific due to tertiary structure
- Active site have complementary shape of substrate
- When substrate and enzyme react, substrate-enzyme formed