1.4- enzymes Flashcards
what is an enzyme?
-a biological catalyst , which control rate of reactions that take place in individual cells or entire organisms
what is a catalyst?
-a substance that changes the rate of a reaction without changing the substances produced
-catalysts are unaffected at the end of the reaction and can be used again
what are the 2 factors which can affect enzymes
pH and temperature
why do enzymes each have a specific shape
-because of the protein structure
-this means they show specificity
2 main types of reactions
1.catabolic
2.anabolic
what is a catabolic reaction
-breaking substances down within a cell
what is an anabolic reaction
-reaction that builds up (synthesises) new molecules in a cell
what is activation energy
-amount of energy substrates need to overcome before they will convert to products
-a barrier
what do enzymes have to do with activation energy
-enzymes are catalysts as they lower the activation energy needed to drive a reaction
what is metabolism
- the sum of the anabolic and catabolic processes in a cell
intracellular vs extracellular enzymes
intra- enzymes that catalyse reactions within the cell
extra- enzymes that catalyse reactions outside of the cell in which they were made
how does temp effect enzyme activity
-low temp= enzymes have too little kinetic energy and move slowly, few successful collisions so low reaction rate
optimum temp= low of KE, lots of successful collisions, high reaction rate
high temp=heat breaks bonds, changing tertiary structure, active site denatured and substrate does not fit, no successful collisions so low reaction rate
temp coefficient
- between 0-40 degrees, rate of reaction doubles for every 10 degrees temp rise
-in humans, it stops completely at 60 degrees
how pH affects enzyme activity
low pH= acidity breaks bonds, maintaining tertiary structure of enzyme, active site denatured, no successful collisions so low reaction rate
optimum pH= many collisions means high reaction rate
high pH= alkalinity breaks bonds maintaining tertiary structure, denatured, no successful collisions
how substrate conc affects enzyme activity
low substrate conc= limits chance of successful collisions, low rate of reaction
high substrate conc= more molecules increases chance of successful collisions, high rate of reaction
what is a substrate
- a reactant which gets altered in a reaction catalysed by the enzyme
what is an IV
- the variable that you change t see what effect it has (cause)
what is a DV
-the variable you measure, as a result of the change in the IV (effect)
what is a control variable
-kept he same
-effects the outcome of the investiagtion
enzyme core prac- what is happening?
-milk protein (casein) is broken down by protease enzymes such as trypsin
-opaque colour of milk replaced by a clear solution
-light passes more easily through this solution, so reaction measured using calorimeter
enzyme core prac- method
- plan dilutions of 1% trypsin solution with distilled water, producing 10cm3 of each conc
2.place 2cm3 of tryspin solution and 2cm3 of d water in cuvette, use as reference to set absorbance to 0
3.measure 2cm3 of milk suspension in second cuvette
4.add 2cm3 t solution in milk cuvette, mix and place in calorimeter, start timer
5.measure absorbance immediately then at 15 sec intervals for 5 mins or until little change
6.rinse cuvette and repeat for all concs
enzyme core prac- dilutions
0.8%= 8ml t, 2ml water
0.6%= 6ml t, 4ml water
0.4%= 4ml t, 6ml water
0.2%= 2ml t, 8ml water
calculating rate from a graph
- draw a tangent to curve
2.draw vertical line and horizontal line to form right angle triangle with tangent
3.read off change in amount of product
4.read off change in time
5.calculate gradient, step3 divided by step4
what is an enzyme inhibitor
-any substance which stops enzymes from working
2 main types of inhibition
-reversible
-irreversible
2 main forms of reversible inhibition
- competitive
- non competitive
reversible inhibition- competitive
-similar shape to substrate
-competes with the substrate to bind to the active site of the enzyme
-inhibition can be reduced by increasing conc of substrate (if amount of inhibitor is fixed)
reversible inhibition- non competitive
-bind to enzyme (not active site) and change its shape
-substrate no longer fits
-so inhibitor does not compete for the active site
-level of inhibition controlled by conc of inhibitor only
irreversible inhibition
-inhibior combines with the enzyme by permanent covelant bonds to one of the groups needed for catalysis to occur
-it changes the shape of the molecule that cannot be reversed
-tends to be slower but effects are more devastating
-e.g. nerve gases such as arsenic
