Wednesday, September 25, 2013

How is sugar made by photosynthesis in a plant cell?Describe the process of photosynthesis and its outcomes.

In a plant, the leaves have pigments (chlorophyll) that absorb light and have openings to let  CO2 through called stroma.


Photosynthesis is the process that plant use to trap the suns energy to build glucose as food.  It happens in the chloroplast. It happens in two stages: the light dependent reaction (happens in the thylakoid membrane of the chloroplast) and the Calvin cycle (happens in the stroma)


The equation for photosynthesis is: C02 + H20 -> C6H12O6 + 02


 The light dependent reaction produced ATP and NADPH, energies that are needed to produce glucose (sugar)


The light dependent reaction has these steps: 


1. The light hits the chlorophyll in the thylakoid membrane, which excites electrons and releases enzymes that split H20 into Oxygen ( which is one of the products of photosynthesis and is released) 


2. The electrons are gained by NADP+, an energy in the electron carrier proteins, which are connected a chain called electron transport chain (ETC, we are gonna call it that from now on, since its shorter to type). Since electrons and hydrogens are gained NADP+ is reduced to NADPH. 


3. As energy goes through the ETC, it is lost.The energy will be used by ADP syththase ( an enzyme) to add PHOSPHATE and produce ATP.



The second stage is the Calvin cycle. The Calvin cycle uses the ATP and NADPH to produce carbon. 


The Calvin Cycle goes as following:


1. 3 molecules of CO2 combine w 3 molecules of RuBp to form 6 molecules of the three carbon sugar PGA (this is called carbon fixation because it fixes CO2 gas into an organic compound) [catalyzed by Rubisco]
2. PGA gains phosphate from ATP and be reduced by NADPH to produced 6 molecules of G3P (PGAL)
3. 1 molecules of PGAL leaves chloroplast to the cytoplasm to be involved in the production of gluclose
4. The 5 molecules of G3P will be used to regenerate RuBP (ATP is required)


The Calvin Cycle produced glucose(C6 H12 06)  

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