Experiments

Question 1

This is an experiment from topic 1A

This is the aparatus for an experiment to measure how fast substrate is broken down.

(The enzme amylase catalyses the breakdown of starch to maltose).

Explain how to carry out the experiment.

Answer 1

• You’ll also need a stopwatch
• A drop of iodine in potassium iodide is put into each well of the spotting tile.
• Then mix together a known concentration of amylase and starch in a test tube.
• A dropping pipette is then used to put a drop of this mixture into one of the wells containing the iodide solution on the spotting tile at regular intervals. Observe the resulting colour.
• The iodine solution goes dark blue-black when starch is present but remains browny-orange when there’s no starch present.
• Record how long it takes for the iodine solution to no longer turn blue-black when starch/amylase mixture is added.
• Repeat the experiment using different concentrations and also three times at each amylase concentration.
• This experiment shows how fast amylase is working to break down the starch! (Basically- How fast substrate is broken down).

Question 2

This is an experiment from topic 1A.

This is the aparatus for an experiment to measure how fast the product of a reaction is made.

(Example: Catalase catalyses the breakdown of hydrogen peroxide and into water and oxygen. You can measure how fast the product is amde by measuring how much oxygen is given off).

Explain how to carry out the experiment.

Answer 2

*The oxygen released displaces the water from the measuring cylinder*

• You may also need a clamp and clamp stand to hold the cylinder upside down. And a stopwatch and a water bath.
• Set up boiling tubes containing the same volume and concentration of hydrogen peroxide. To keep the pH constant, add equal volumes of a suitable buffer solution to each tube.
• Set up the rest of the apparatus (as shown).
• Put each boiling tube in a water bath set to a different temperature (e.g. 10 Degrees Celcius, 20 Degrees Celcius, 30 Degrees Celcius and 40 Degrees Celcius), along with another tube containing catalase. Wait 5 minutes before moving onto the next step so that the enzymes get to the right temperature.)
• Use a pipette to add the same volume and concentration of catalase to each boiling tube. Then, quickly attatch a bung and delivery tube.
• Record how much oxygen is produced in the first minute (60 s) of the reaction. Use a stopwatch to measure the time.
• Repeat the experiment at each temperature three times, and use the results to find an average volume of oxygen produced.
• Calculate the averatge rate of reaction at each temperature by dividing the volume of oxygen produced by the time taken (i.e. 60 s). The units will be cm^3s^-1.