Enzymes year 1 Flashcards
describe the lock and key model and the ‘induced fit’ model
key model:
-substrate is complimentary to the active site of enzyme, and fits exactly into form a enzyme-substrate complex
Induced fit
- Substrate is SIMILAR to the same of the active site,
- when substrate fits into the active site the enzyme slightly changes its shape to form ENZYME-SUBSTRATE COMPLEXES
- Substrate bonds are put UNDER STRAIN/STRESS
Explain how enzymes act as biological catalysis (7 points)
- Substrate has a SIMILAR shape to active site
- Substrate fits into the active site
- Changes the actives sites shape slightly when bonding with the substrate- forms an ES-COMPLEX
- LOWERS ACTIVATION ENERGY
- Substrate bonds are put UNDER STRAIN/ STRESS
- Substrate forms into product
- Product is released and active site goes back to its original shape.
Explain how these 4 factors affect the rate of enzyme catalysed reaction
- Temperature
- PH
- substrate concentration
- Enzyme concentration
Temperature-Raising up the temperature from up to OPTIUM TEMP, increases KINETIC energy means more successful collisions so more enzyme-substrate complexes formed, so more product is produced.
ABOVE OPTIMUM decreases the RATE of reaction as it denatures the enzyme- bonds in tertiary structure break so active site is broken.
PH- changing ph anything from its optimum will denature the enzymes as tertiary structure is distorted therefore distorting the active sites shape.- FEWER ES-complexes formed.
Substrate concentration- at lower conc NOT all enzymes active sites are occupied, increasing substrate concentration increases likely hood of successful collisions -more ES-complexes formed, more products. At HIGH conc of substrate it will have no effect on the rate as all the active sites are occupied, its at its maximum rate- Vmax.
Enzyme conc-increasing the concentration of enzyme increases the rate of reaction.
Proportional.
More active sites become available so more ESCs can form at any point forming product faster.
What is protein denaturation
- heat/ph can cause changes in R GROUPS INTERACTIONS within the enzyme.
- Therefore tertiary structure of the POLYPEPTIDED is disrupted
- Hydrogen/disulphide bridges/ionic bonds are broken
- polypeptide structure unfolds
- ACTIVE SITE IS DESTROYED
- Substrate CANT BOND to the active site and therefore no ES-COMPLEXES FORMED
- permanent damage
what’s a control
where you remove what is responsible for the change you observe (So with enzymes you would have a separate tube where the enzyme has been boiled (denatured).
This can then be compared)
explain and describe the role of a competitive inhibitor
- Have a similar shape to the substrate
- Fit into the enzymes active site
- Prevents Substrate from binding to make a ES-complex
- Increasing substrate concentration dilutes the effect of competitive inhibitors
Explain and describe the role of non-competitive inhibitors
-Bind to a site OTHER THAN THE ACTIVE SITE
-causes the active site of enzyme to change its shape
-prevents substrates from binding and creating enzyme-substrate complexes
(Increasing substrate concentration CANNOT dilute a competitive inhibitor effect!)
Explain enzyme feedback inhibition with biochemical pathways.
if a lot of a product is produced on the end of an enzyme pathway the product will act as a NON-COMPETITIVE inhibitor for the first enzyme-turns off its own production
If production is used up elsewhere there will be LESS FEEDBACK INHIBITION so more product is made
process is self regulated
Draw and explain a typical ‘product-time’ graph
Reaction is fastest at start as there is more substrate and a higher frequency / more ESCs can form.
Reaction slows as substrate is being converted to product, so ESCs forming less often / fewer.
Eventually all the substrate has been converted to product (reaction stopped / plateau)..
