The reactions occurring in a living organism are classified as metabolism, it sums up all the chemical reactions occurring in a living thing. Organism rely on metabolism, and ambient temperature can have significant effects on the metabolism of the organism. There is also an inverse relationship between an organism's rate of metabolism and their size. This is because the smallest has a larger volume-to-volume ratio and the environment loses more heat. It is also considered that metabolism is highly inefficient. This is because there is only about 40% of the total energy that is extracted in the process in a useful form. In the form of heat, the rest of the energy is lost.
In this experiment, we will continue the tracks of photosynthesis like the previous experiment but in this study we have have to focus on cellular respiration as well. Both a photoautotroph, green algae and a heterotroph, small aquatic snails will be used to determine the ties between photosynthesis, cellular respiration and carbon cycling. This experiment was introduced as such so that it could be investigated the ties between photosynthesis, cellular respiration and carbon clycling when observed under different conditions.
The more CO2 in an aqueous solution, the more acidic it becomes the solution. The experiment's algal beads will be surrounded by a solution of CO2 markers. Because CO2 is used for photosynthetic reactions, this means that the solution undergoes a color change. The solution is yellow-orange when there is relatively more CO2. The colour tends to purple when CO2 is used.
Materials and Method
In this experiment, an alternate protocol was used which was given to us by the TA. We didn’t use the experiment given in the Lab manual.
Instead of using elodea leafs, crayfish and snails in flask to observe the metabolism and the photosynthetic cycle; we used algal beads and freshwater aquatic snails for this experiment. Each group in the class was given a cuvette. There were 8 cuvettes, 1.5 mL of CO2 indicator was added to all the cuvettes. The first four cuvettes that were supposed to be kept in the light had : 1. Just indicator, 2. Indicator and bead, 3. Indicator and snail, 4. Indicator, beads and snails. The next four cuvettes that were kept in the dark had: 5. Only indicator, 6. Indicator and Beads, 7. Indicator and snails, 8. Indicator, beads and snails. We had to observe the cuvette for about 45 minutes and record the pH for every five minutes. We recorded the ph for time 0 minutes before starting the experiment. We had to cover the dark cuvettes with layers of foil. And then keep all the cuvettes under 30cm distance lamps, making sure that the beads and in some the beads and the snails are in a single layer. We then had to record the ph change for every give minutes by observing the color change of the CO2 indicator. And always wrapping the dark cuvettes back with foil after observing the ph change as quickly as possible.
Discussion & conclusion
The pH in the cuvette kept in Light with indicator and beads increased due to photosynthesis and cellular respiration, using up most of the CO2. But in the cuvette kept in light with Indicator and snails, the pH is low at 6.9 due to no photosynthesis occurring in order to intake the CO2 produced by snail. In the cuvette kept in the light with indicator and both snails and algal beads, the pH was high at 8.9 because the algal beads were undergoing photosynthesis and using the CO2 produced by the snails as well.
The pH of the cuvettes in light and dark conditions stay constant as there is no activity happening due to nothing other than the indicator placed in it.
The pH of the cuvette kept in dark with indicator and Beads was higher than the ones kept in dark as well but with snails and the other one with snails and beads both. It is because, the algal beads were undergoing cellular respiration but were not photosynthesizing due to lack of light. The cuvettes kept in dark with indicator and snails have a low ph due to no photosynthesise taking place and hence all the CO2 produced by the snails is not getting used up. The ph of the cuvette with indicator and both snail and beads is relatively the lowest because of the cellular respiration of the algal beads producing CO2 including the CO2 production by the snails and due to the lack of light photosynthesis is not taking place to intake the CO2 produced.
The lesser the surface area an organism takes, greater the metabolic rate of the organism. The metabolic rate of an organism increases with its temperature. The more a plant is exposed to light, greater the metabolism. The sources of error could be the heat of the light source for the ones kept in light, which could affect the photosynthesis but for the dark cuvettes it wouldn’t be a problem as we wrap them with foil which keeps the conditions constant.
In an enclosed surrounding, the rate of photosynthesis needs to be the same as the cellular respiration for sustainability because then there will be an equilibrium of both the gases. CO2 and O2. DIBS cuvette would be more basic as there will be more CO2 produced and no photosynthesis to intake the CO2 due to lack of light. And vice versa for the LIBS as the algal beads are increased, which will under go photosynthesis using up the CO2.
In LIBS it would be a little more acidic as there will be more CO2 due to cellular respiration but the photosynthesis is also taking place to intake the CO2 produced. In DIBS it will be way more acidic as there is no photosynthesis taking place due to lack of light to intake the CO2 produced by cellular respiration. Chloroplast used ATP produced by photosynthesis to produce glucose and mitochondria released ATP and uses it to create more.
- Krane, D. (2018-2019). Bio 1120: A Laboratory Perspective. Cincinnati, OH: Van-Griner