Respiration

Question 1

how is oxygen uptake calculated using a respirometer?

Answer 1

-adding potassium hydroxide (KOH) to the respirometer
-the living organisms take in oxygen from within the system
-carbon dioxide produced through respiration is absorbed by KOH
-The reduction in pressure causes the dye to move in the direction of the biological material
-distance moved represents oxygen used in respiration.

Question 2

how is carbon dioxide production calculated using a respirometer?

Answer 2

-replacing KOH with water
-respirometer needs to be left for the same length of time and in the same conditions as when measuring O2
-CO2 produced is not absorbed
-if dye in the manometer does not move then the volume of carbon dioxide produced is the same as the volume of oxygen absorbed

Question 3

how can you tell if more carbon dioxide is produced than oxygen taken in?

Answer 3

dye moves away from the living material

Question 4

how can you tell if less carbon dioxide is produced than oxygen taken in?

Answer 4

dye moves closer to the living material.

Question 5

how is the respiratory quotient calculated?

Answer 5

volume of CO2 released
_________________________
volume of O2 consumed

Question 6

how can temperature be controlled during the respirometer experiment?

Answer 6

placing the apparatus in a water bath at the same temperature for both parts of the investigation

Question 7

why must the temperature be controlled?

Answer 7

-It will affect the respiration rate and consequently oxygen and carbon dioxide production.

Question 8

what are redox indicators and what do they do?

Answer 8

-they’re chemicals
-they are a different colour when they’re reduced compared to when they’re oxidised, demonstrating dehydrogenation.

Question 9

what colour is methylene blue when it is oxidised?

Answer 9

blue

Question 10

what colour is methylene blue when hydrogen from respiration causes it to be reduced?

Answer 10

colourless