Photosynthesis Essay

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Photosynthesis is an essential reaction that can be carried by chloroplast in the plant. (Campbell, pg. 175). Inside the chloroplasts, thylakoids contain pigments such as chlorophyll that play major role in photosynthesis. (Citovsky, Lecture 10).

Photosynthesis are composed of light reactions and Calvin cycle. Light reactions required the light to initiate photoexcitation. Photoexcitation happened when the light strike on chlorophyll, the electron will be excited and transferred around the antenna pigment molecules. Electrons will then be transferred to a reaction-center complex. Such system is called photosystem (Campbell et al., pg. 194). In photosystem, excited electron will go around the antenna pigments. The electron will be transferred from antenna center to reaction center of chlorophyll a. Then the
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Calvin cycle will be divided into carbon fixation, reduction and regeneration of carbon dioxide acceptor. Carbon fixation involves the binding of carbon dioxide to carbon dioxide acceptor (RuBP). The catalyst for this reaction is RUBISCO. The second phase of Calvin cycle, reduction involves the synthesis of glyceraldehyde-3-phosphate(G3P) by using NADPH and ATP that are obtained from light reaction. 6 molecules of G3P are synthesized from the second phase for every 3 molecules of carbon dioxide. However, only one carbon dioxide will enter the cycle every time (Campbell et al., pg. 200). Out of 6 molecules of G3P, only 1 molecule of G3P will be exported for synthesis of other organic molecule such as glucose. 5 of the G3P will be used to synthesize RuBP for the continuation of Calvin cycle (Citovsky, Lecture …show more content…
Based on the description above, splitting of water only occur in light reaction. And this breakdown is the major source for the release of oxygen (Citovsky, Lecture 21). Therefore, choice A, is the correct

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