C1.2 - measuring respiration rate (3o)

Question 1

what are the 4 factors that affect the rate of cell respiration?

Answer 1

1. oxygen concentration
2. respiratory substrate availability
3. temperature
4. cell type

Question 2

how does oxygen concentration affect cell respiration?

Answer 2

• lower concentrations of oxygen decrease the rate of aerobic cell respiration
• when ATP cannot be produced quickly enough, anaerobic respiration occurs

Question 3

how does cell type affect cell respiration?

Answer 3

some cells require more energy than others due to their metabolic reactions

Question 4

how does respiratory substrate availability affect cell respiration?

Answer 4

lower concentrations of glucose decrease respiration rate

Question 5

how does temperature affect cell respiration?

Answer 5

respiration is controlled by enzymes, so temperatures above and below the optimum reduce the activity of these enzymes and reduce respiration rate

Question 6

how can a respirometer be used to measure rate of cell respiration?

Answer 6

a respirometer is an apparatus used to determine the rate of cell respiration

1. an alkali is used to absorb carbon dioxide so the rate of oxygen production can be measured
2. the starting position of the drop is measured
3. the distance the drop moves is dependent on the change in pressure and oxygen consumption
   - as oxygen is consumed and carbon dioxide is absorbed, the pressure in the respirometer decreases
4. the determine the volume of oxygen, the cross-sectional area of the capillary tube is multiplied by the distance the drop moves

Question 7

what are limitations of a respirometer?

Answer 7

temperature and external pressure can affect the position of the water droplet

Question 8

how can accuracy be improved for a respirometer?

Answer 8

second control tube is connected to the experimental tube by a nanomter tube

Question 9

what are more modern techniques of measuring respiration rate?

Answer 9

more modern techniques include:
- using a pressure monitor with an alkali to absorb carbon dioxide so pressure reduction can be used to measure oxygen consumption
- using oxygen monitors or oxygen probes to measure the change of oxygen concentration over time

Question 10

how does a more complex respirometer work?

Answer 10

a coloured fluid in the manometer moves towards the tube with the lower pressure and the rate at which it moves measures oxygen consumption rate

Question 11

what happens in a complex respirometer if there are variations in temperature?

Answer 11

variations in temperature affects pressure in both tubes equally, so the fluid doesn’t move as the glass beads and water means there is an equal volume of air in each tube

Question 12

what happens to the number of air molecules over time in a simple respirometer?

Answer 12

number of air molecules decreases

Question 13

what happens to the pressure over time in a simple respirometer?

Answer 13

pressure decreases

Question 14

what happens to the drop of liquid in the boiling tube over time in a simple respirometer?

Answer 14

drop of liquid moves towards the respirometer as it has lower pressure than the atmosphere

Question 15

what is gas exchange?

Answer 15

gas exchange is the diffusion of oxygen and carbon dioxide in opposite directions across a cell membrane

Question 16

what is the direction of gas movement during gas exchange?

Answer 16

oxygen diffuses out of the alveolar air and into the bloodstream by crossing membranes of the alveolar and capillary cells, with carbon dioxide diffusing in the opposite direction