Photosynthesis Essay Example | Topics and Well Written Essays - 500 words

Photosynthesis - Essay Example The molecule is made up of a porphyrin ring with several carbon and nitrogen bonds and a magnesium ion in the center (Starr et al., 2009). The first part of photosynthesis is the light dependent reaction occurring in the thylakoid membrane. Here chlorophyll and other accessory pigments like beta carotene absorb different wavelengths of light in the antenna complex (Starr et al., 2009). When one chlorophyll pigment absorbs a photon of light in photosystem II, the molecule reaches a higher energy state, exciting its electron. This excitation results in the loss one electron which is then passed down the electron transport chain via electron carriers. The excited electron is transferred to another chlorophyll molecule in photosystem I creating a proton gradient. The transfer of electron results in the reduction of co-enzyme NADP to NADPH (Starr et al., 2009). The created energy also helps hydrogen ions to move across the thylakoid membrane. Also at the end of the proton gradient, the enzyme ATP synthase converts ADP to ATP by a process called photophosphorylation where the converted light energy will be stored (Starr et a l., 2009). A water molecule is also split though the process of photolysis resulting in an oxygen molecule and allowing the chlorophyll pigment to regain its lost electron. Therefore, at the end of the first cycle the resulting molecules are 3 ATP, 1 oxygen, and 2 NADPH (Starr et al., 2009). The second part of the process is called the light independent reaction and occurs in the stroma within the chloroplasts and is used to take the carbon dioxide molecule and convert it into sugar. Although, it doesn’t need the light, this part of photosynthesis relies on the products ATP and NADPH to drive its process, the Calvin cycle. The enzyme RuBisCO takes the carbon dioxide molecule and uses it to catalyze RuBP (Starr et al., 2009). The carbon dioxide combines with this 5-carbon molecule in a process called carbon fixation and produces 2