Hello, my question is on investigating the uptake of oxygen by organisms using respirometers. I just don't understand how in this case (in the explantation) when the volume of oxygen decreases, the pressure inside the tube decreases? Because if organism take up the oxygen there'll be even less gas, so how can pressure increase?
Answers
Answer:
Explanation:
Using a respirometer
In this activity we will look at three practicals which can support students understanding of respiration and challenge misconceptions.
As you watch the videos, we’d like you to make a note of any misconceptions which could be addressed by each of the three practical investigations. You’ll choose one of these practicals, and the misconceptions it addresses, to devise your own diagnostic question in step 2.11
Using a respirometer
This video demonstrates how the rate of aerobic respiration in germinating pea seeds can be compared to the rate of aerobic respiration in dormant pea seeds. The rate of oxygen consumption will be used to determine the rate of aerobic respiration and will be measured using a very simple respirometer.
It will also allow some common misconceptions to be tested: for example, that seeds are dead and therefore won’t respire, or if they are not dead, they are from plants and therefore will only respire at night.
This simple respirometer can be used to investigate cellular respiration in living organisms. The rate of respiration of germinating and non-germinating peas in this experiment is determined by the consumption of oxygen. Potassium Hydroxide (KOH) is used to alter the equilibrium. Potassium hydroxide removes the carbon dioxide and oxygen is used by cellular respiration thus decreasing the volume of gas in the respirometer.
The recorded observations show that after 20 minutes, a large volume of water has moved into the pipette in respirometer A, a small volume of water has moved into the pipette in respirometer B and no water has moved into the pipette in respirometer C.
The germinating peas in tube A have used up the most oxygen and have the highest rate of respiration. The dry (dormant) seeds in tube B have used up a smaller volume of oxygen, demonstrating that they are carrying out respiration at a slow rate, The tube of glass beads was set up as a control, to investigate whether something other than the respiring peas was using up the oxygen in the tube. No water entered the pipette in the control experiment, so the glass beads were an effective control.