Electron Transport Chain Experiment

...

DISCUSSION

Plants cannot use light energy directly to make sugars. Instead, the plant changes the light energy into a form it can use: chemical energy. The chemical energy that plants use is stored in ATP and NADPH. ATP and NADPH are two kinds of energy-carrying molecules. Plants need water to make NADPH. This water is broken apart to release electrons (negatively charged subatomic particles). When water is broken it also creates oxygen.

The electrons must travel through special proteins stuck in the thylakoid membrane. They go through the first special protein (the photosystem II protein) and down the electron transport chain. Then they pass through a second special protein (photosystem I protein)

DCPIP use in this experiment which is a blue compound acts an electron acceptor. The light dependent reaction take place in thylakoid membrane inside chloroplast. The thylakoid membranes of the chloroplasts are mechanically disrupted so that the natural electron transport chain no longer functions normally. When light strikes the chloroplasts, the DCPIP is reduced by the excited electrons from chlorophyll, and it changes from its original blue color to colorless as it accepts the electrons. However, in tube 3, chloroplast is not present therefore no change in blue colour.

A buffer is used in this experiment as it is a mixture of molecules that release or bind H+ in order to maintain a relatively stable pH, therefore pH of the solution would not change. The re-suspension buffer is used in experiment to rupture the chloroplast envelope, allowing for protons to flow freely from solution into the thylakoid membranes, which do not rupture.

CONCLUSION

The first error that may happen during the experiment is not covering the test tube with aluminium foil carefully causing the sunlight able to penetrate the tube and affect the result. Second, contamination of exterior substances may occur without proper precaution when handling test tubes and measuring cylinder. Third, parallax error may occur when measuring volume using measuring cylinder where the student is not using the correct method to observe.

Furthermore, the first precaution steps for the experiment is to make sure to wrap the test tubes with aluminium foil neatly to prevent light from affecting the result of the experiment. Secondly, make sure to rinse the test tubes and measuring cylinder with distilled water and corresponding solution before using to avoid contamination from happening. Third, make sure the eye of the observer is perpendicular to the scale when measuring solution to avoid parallax error. By avoiding all the possible errors, much accurate results will be produced.

As stated in Surah Az-Zumar“…Indeed, the patient will be given their reward without account.” [az-Zumar 39:10], Allah explains that we have to be patient in everything in order to get a good result while test our hearts to improve our iman. Being patient while waiting for the result and follow all the rules that are provided for us even though it takes time. But in the end of the day, we manage to get the result accurately and satisfied with our work.

REFERENCES

1. Pearson - The Biology Place. (n.d.). Retrieved from http://www.phschool.com/science/biology_place/labbench/lab4/dpipex.html

2. Light-Dependent Reactions of Photosynthesis | CAPP. (n.d.). Retrieved from https://cambridgecapp.wordpress.com/improving-photosynthesis/photosynthesis/light-dependent-reactions-of-photosynthesis/

3. Light-Dependent Reactions of Photosynthesis | CAPP. (n.d.). Retrieved from https://cambridgecapp.wordpress.com/improving-photosynthesis/photosynthesis/light-dependent-reactions-of-photosynthesis

4. Department of Plant Science. (2017). Laboratory Manual SPL 1113/SAP1113 General Chemistry for Plant Science/ Applied Plant Science. Kuantan: International Islamic University Malaysia.

QUESTIONS

- Why was there some colour change in the wrapped tube? Does electron transport occur without light?

The colour change indicates that photosynthesis occurred as the blue colour of DCPIP change to colourless thus lighten the colour of the solution thru reduction process. Yes, electron transfer without light is possible as the solution underwent the dark reaction of photosynthesis.

- Are there electrons being accepted in tube 1# even though there’s no DCPIP present? Explain your answer.

Electrons are still accepted in the solution even though DCPIP is not present. DCPIP is merely an electron transfer indicator and have no effect in photosynthesis process. In the presence of water and light photosynthesis will occur.

...