Prac pt 2

Question 1

What are the methods for collecting data from a catalase investigation? 4

Answer 1

Counting oxygen bubbles

Measuring height of foam

Downward delivery & displacement

Gas syringe

Question 2

What is downward delivery and displacement? 3

Answer 2

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

Question 3

What is a disadvantage of downward delivery displacement?

Answer 3

Oxygen leaks once the reaction starts, can lower oxygen reading

Question 4

How do you use a gas syringe?2

Answer 4

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

Question 5

What is the initial rate of reaction?

Answer 5

The rate of product formation at the beginning of the reaction when the substrate concentration is stable

Question 6

How do you plot the initial rate of reaction? 4

Answer 6

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

Question 7

How do you calculate the rate of reaction?2

Answer 7

Calculate the gradient of the tangent you drew

Change y/change x

Question 8

What does catalase do?

Answer 8

Breaks down hydrogen peroxide into water and oxygen

Question 9

What does Amylase do?

Answer 9

Catalyses breakdown of starch (a polysaccharide) into Maltose (a disaccharide)

Question 10

Where is Amylase found?

Answer 10

Saliva and walls of small intestine

Question 11

What are the methods of collecting data for Amylase reaction?2

Answer 11

Colour change with potassium iodide/iodine solution

Colourimeter to measure colour of sample at different intervals

Question 12

What is one way to control pH in an experiment?

Answer 12

Use a pH buffer

Question 13

What is happening at 1 on graph of temperature’s effect on enzyme rate of reaction 4

Answer 13

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

Question 14

What is happening at 2 on graph of temperature’s effect on enzyme rate of reaction 3

Answer 14

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

Question 15

What is happening at 3 on graph of temperature’s effect on enzyme rate of reaction 2

Answer 15

This is the point where the temperature reaches optimum limit

Which is the highest point where an enzyme can work without being denatured

Question 16

What is happening at 4 on graph of temperature’s effect on enzyme rate of reaction 4

Answer 16

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

Question 17

What is happening at 5 on graph of temperature’s effect on enzyme rate of reaction 4

Answer 17

The enzyme’s active site is completely changed now

So substrate no longer fits

Enzymes are fully denatured

Rate of reaction is at 0

Question 18

How do you control temperature in enzyme investigation?

Answer 18

Water bath

Question 19

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

Answer 19

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

Question 20

What does the enzyme tripsin do?

Answer 20

Digests fats, like in milk or milk powder

Question 21

How do you investigate the enzyme tripsin? 3

Answer 21

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

Question 22

Look at graph of substrate concentration, what is happening at 1? 3

Answer 22

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

Question 23

Look at graph of substrate concentration, what is happening at 2? 2

Answer 23

As the substrate concentration increases, more particles are available

More enzyme-substrate complexes increase the rate of reaction

Question 24

Look at graph of substrate concentration, what is happening at 3? 2

Answer 24

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

Question 25

Look at graph of substrate concentration, what is happening at 4? 4

Answer 25

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