respiration experiments

Question 1

1. What piece of equipment can be used to measure
   the respiratory rate?

Answer 1

Respirometer

Question 2

2. Describe how the equipment below can be used
   to measure the rate of anaerobic respiration of cells
   in a liquid culture e.g. yeast cells.

Answer 2

The yeast suspension is placed in a chemical flask connected to a delivery tube, a bung is used to seal the flask, a layer of oil or paraffin is floated on top to prevent oxygen dissolving into the water. The delivery tube is connected to a gas syringe. · Allow time for the oxygen to be absorbed/used to make conditions anaerobic · As the yeast respires it releases CO2 which increases the volume of gas in the flask and syringe and pushes the plunger outwards · The volume of carbon dioxide collected in the gas syringe after a period of time is recorded · The rate of respiration is calculated using the equation rate = volume of gas Time · The experiment is repeated in different conditions e.g.different temperatures/different respiratory substrates.

Question 3

3. Describe how the equipment below can be used
   to measure the rate of anaerobic respiration of cells
   in a liquid culture e.g. yeast cells.

Answer 3

The yeast suspension is placed in a chemical flask connected to a delivery tube, a bung is used to seal the flask, a layer of oil or paraffin is floated on top to prevent oxygen dissolving into the water. The delivery tube delivers any gas produced through limewater · Allow time for the oxygen to be absorbed/used to make conditions anaerobic · As the yeast respires it releases CO2 which is bubbled through the limewater forming a precipitate. · The precipitate is filtered away from the limewater and its mass measured · The rate of respiration is calculated using the equation rate = mass of precipitate Time The experiment is repeated in different conditions e.g. different temperatures/different respiratory substrates.

Question 4

4. Describe how the equipment below can be used
   to measure the rate of anaerobic respiration of cells
   in a liquid culture e.g. yeast cells.

Answer 4

The yeast suspension is placed in a chemical flask connected to a delivery tube, a bung is used to seal the flask, the delivery tube contains coloured ink, alkaline pyrogallol absorbs oxygen to make conditions anaerobic. · Allow time for the oxygen to be absorbed/used to make conditions anaerobic · As the yeast respires it releases CO2 which will increase the volume of gas in the flash and push the coloured ink to the right. · The distance moved by the ink in a given time period is recorded · The volume of gas release can be calculated if we know the radius of the delivery tube. · The rate of respiration is calculated using the equation rate = volume of gas

Time · The experiment is repeated in different conditions e.g. different temperatures/different respiratory substrates.

Question 5

5. How can the method above be modified to
   measure the rate of aerobic respiration?

Answer 5

Swap pyrogallol for sodium hydroxide to absorb carbon dioxide instead of oxygen · The ink will move towards the right due to a reduction in the volume of gas inside the beaker as oxygen is used up.

Question 6

6. Describe how a redox indicator can be used to
   measure the rate of respiration of yeast cells in
   solution

Answer 6

A redox indicator like DCPIP or methylene blue can be used to indicate respiration occurring * During respiration, electrons are transferred by redox reactions along the electron transport chain * These chemicals accept electrons and become reduced. This changes their colour to colourless. * The time taken to become colourless is recorded. * Rate is then calculated using 1/time

Question 7

5. Describe the principles of a simple respirometer
   that measures the rate of aerobic respiration of
   small organisms e.g. woodlice.

Answer 7

Sodium hydroxide absorbs the CO2 released by the insect as it respires. · The equipment is air tight so any oxygen used up will cause a pressure change inside the tubing · The coloured liquid will move towards the animal · The opposite side is a control test using glass beads of equal mass to the insect. This balances any changes in pressure caused by anything other than respiration of the insect. · The volume of gas release can be calculated if we know the radius of the tube. · The rate of respiration is calculated using the equation rate = volume of gas/ time

Question 8

6. What chemical absorbs oxygen to make

conditions anaerobic?

Answer 8

Pyrogallol

Question 9

7. What chemical absorbs carbon dioxide?

Answer 9

odium hydroxide/potassium hydroxide

Question 10

8. What chemical can be placed on top of a liquid
   suspensions of cells to prevent oxygen dissolving
   into the solution and hence causing anaerobic
   conditions (once all oxygen in the liquid has been
   used up)

Answer 10

· Oil/paraffin