pag respirometer

Question 1

what does respirometer measure

Answer 1

rate of oxygen consumption in aerobic respiration

Question 2

what is the purpose of the soda lime

Answer 2

to absorb CO2 produced so volume of O2 absorbed can be measured

Question 3

why does the apparatus need to be airtight

Answer 3

prevent air entering or leaving as this would affect volume and therefore pressure, which would affect movement of coloured liquid

Question 4

which way does the liquid move and why

Answer 4

• towards experimental tube containing organism
• organism takes in oxygen for respiration
• volume decreases in test tube so pressure decreases in test tube
• pressure in control tube/syringe is comparatively higher
• liquid moves towards experimental tube

Question 5

units for respiration rate

Answer 5

volume per time

eg cm3 min-1

Question 6

what is in the control test tube

Answer 6

glass beads of same mass as organism in other test tube

Question 7

limitations

Answer 7

• oxygen uptake may not be a good representation of respiration rate
• oxygen could leak
• difficult to read meniscus

Question 8

control variables

Answer 8

• mass of organisms
• temperature (use water bath/thermometer)
• mass of soda lime
• syringe size if used

Question 9

describe how you would add the red fluid to the capillary tube at the start of the experiment

Answer 9

capillary tube dipped into a small beaker of red fluid and allowed to
run

Question 10

what info is needed to compare oxygen uptake between organisms

Answer 10

mass used

Question 11

how would the experiment differ using a seed and a small animal

Answer 11

• ethical use of animal eg screen so it cannot touch soda lime
• bigger syringe needed for animal

Question 12

what is measured and why

Answer 12

• distance moved by fluid in capillary tube
• gives rate of oxygen uptake
• to estimate rate of aerobic respiration