Prac pt 2 Flashcards
What are the methods for collecting data from a catalase investigation? 4
Counting oxygen bubbles
Measuring height of foam
Downward delivery & displacement
Gas syringe
What is downward delivery and displacement? 3
As oxygen is produced, it travels along capillary tubing to an inverted measuring cylinder
Cylinder has been filled with water so when oxygen bubbles through, it forces water out the cylinder and collects it at the top
Can take a reading of the volume of oxygen using a scale on the side of the cylinder
What is a disadvantage of downward delivery displacement?
Oxygen leaks once the reaction starts, can lower oxygen reading
How do you use a gas syringe?2
Arrange it horizontally so that the plunger isn’t affected by gravity
Plug the beaker with the rubber stopper as soon as possible after starting reaction
What is the initial rate of reaction?
The rate of product formation at the beginning of the reaction when the substrate concentration is stable
How do you plot the initial rate of reaction? 4
Draw a smooth line of best fit through points
Draw tangent to curve at start of data
Make triangle as big as possible
Find place to stop drawing on easily readable part of scale
How do you calculate the rate of reaction?2
Calculate the gradient of the tangent you drew
Change y/change x
What does catalase do?
Breaks down hydrogen peroxide into water and oxygen
What does Amylase do?
Catalyses breakdown of starch (a polysaccharide) into Maltose (a disaccharide)
Where is Amylase found?
Saliva and walls of small intestine
What are the methods of collecting data for Amylase reaction?2
Colour change with potassium iodide/iodine solution
Colourimeter to measure colour of sample at different intervals
What is one way to control pH in an experiment?
Use a pH buffer
What is happening at 1 on graph of temperature’s effect on enzyme rate of reaction 4
At low temperatures, particles moving slowly have little kinetic energy
So a low number of collisions
Particles that do collide don’t have the energy needed to break and form bonds
Very few enzyme-substrate complexes formed
What is happening at 2 on graph of temperature’s effect on enzyme rate of reaction 3
As temperature increases, number of successful collisions increases
Because particles are moving with more energy, substrate is colliding with active sites more
Also colliding with enough energy to break/form bonds needed to create the product
What is happening at 3 on graph of temperature’s effect on enzyme rate of reaction 2
This is the point where the temperature reaches optimum limit
Which is the highest point where an enzyme can work without being denatured
What is happening at 4 on graph of temperature’s effect on enzyme rate of reaction 4
There is too much kinetic energy of enzymes and substrate
Bonds holding the enzyme in precise shape start to break
Hydrogen bonds that hold the active site together start to break and the active site deforms, so the enzyme is now denatured
The shape is only slightly affected, so some enzyme-substrate complexes are still formed, just slower
What is happening at 5 on graph of temperature’s effect on enzyme rate of reaction 4
The enzyme’s active site is completely changed now
So substrate no longer fits
Enzymes are fully denatured
Rate of reaction is at 0
How do you control temperature in enzyme investigation?
Water bath
How do you record the results of an investigation on enzyme concentration, using different concentrations of enzymes where you collect the data every 30 seconds per enzyme concentration 4
Plot the data on a line graph with x being time and y being data measured e.g. oxygen collected
Each line represents a different enzyme concentration (see notes)
Then find the initial rate of reaction on each line
plot another line graph of Initial rate of reaction on y & enzyme concentration on X
What does the enzyme tripsin do?
Digests fats, like in milk or milk powder
How do you investigate the enzyme tripsin? 3
Milk powder will be dissolved in water, so will be cloudy
Add tripsin and as it reacts on substrate the solution will be clearer
Measure colour change with colourimeter
Look at graph of substrate concentration, what is happening at 1? 3
There is a low substrate concentration
Not many collisions occurring because not enough particles
Very few enzyme-substrate complexes are formed & most active sites are empty
Look at graph of substrate concentration, what is happening at 2? 2
As the substrate concentration increases, more particles are available
More enzyme-substrate complexes increase the rate of reaction
Look at graph of substrate concentration, what is happening at 3? 2
Lots of substrate particles, nearly all active sites are occupied
The rate starts to level off because it’s harder for a substrate to find an active site to form enzyme-substrate complexes with
Look at graph of substrate concentration, what is happening at 4? 4
This is the maximum speed that the reaction can reach at this enzyme concentration
All active sites are occupied, so no more enzyme-substrate complexes can be formed
The reaction hasn’t stopped, because as soon as an active site is available, it’s filled
Adding more substrate will have no effect on rate of reaction
