Ben Friesen
AP Biology
To begin, we must note the equation for the complete oxidation of glucose:
The first thing which we did was obtain a tub of water at room temperature (18 degrees Celsius). A group opposite ours put ice in their tub to obtain a 10 degree temperature. With this one exception, their procedure mimicked ours. Those results are at the end of this paper. We then obtained a 50 mL graduated cylinder, marbles, 50 dry beans, and 50 germinating beans.
We filled the graduated cylinder with 30 mL of water and then began dropping the germinating beans into the water. The water level had risen to 44 mL, so we reasoned that the beans took up 14 mL of space. We then took the beans out of the tube and patted them with a towel to soak up some of the moisture. After that we filled the graduated cylinder up to 30 mL again and put in the dry beans. This raised the water level to far less than 44 mL, so we put in some marbles (four of them) to make both batches equal in volume. We emptied the cylinder again and put the beans and marbles in a separate pile from the first. We refilled the graduated cylinder to 30 mL and began dropping in marbles. This was to be our control. It took eight marbles to get the total volume to equal 44 mL.
We then got three vials and placed cotton soaked with KOH in them. Then we added a layer of paper towel to prevent the KOH from touching the beans. After that we put each batch into a vial, put the stopper and pipette into each, and lowered them into the water with the end of the pipette hung above the water by a tape sling, and the other end weighted down. We let them equilibrate for ten minutes before fully submerging them into the water.
After they had been submerged, we measured the distance of the end of the resulting air bubble from the open end of the pipette. This step was repeated at five minute intervals three more times. Those results, and the ones from the ice water bath, can be seen below.
In this lab the KOH reacted with the CO2 formed by the break down of the sugar to make a solid, essentially getting rid of the CO2 and reducing the amount of air in the vial. This caused more matter to be sucked into the tube to equalize the pressure, and thus made the air bubble move. As we can see by the graphs, germinating seeds respire, and dry seeds (and marbles) don’t. Also, their efficiency is lowered as temperature decreases.
The lab, in simplified terms, measured the effectiveness of respiration by looking at the amount of oxygen consumed. We performed the experiment on three different groups and each under two different temperatures.
