Chapter 10: Photosynthesis I. Photosynthesis in Nature 1) Autotrophic nutrition requires that the organisms make food without eating other organisms or their by-products, while heterotrophic nutrition is the exact opposite, with organisms eating others and their by-products. 2) Photoautotrophs use light as a source of energy to synthesize organic substances, and chemoautotrophs produce their organic compounds without the help of light, obtaining their energy by oxidizing inorganic substances, such as sulfur or ammonia. 3) The chloroplast contains chlorophyll, and it is mainly found in the cells of mesophyll. There are also stomata on the leaves to allow oxygen exiting. Chloroplasts are watermelon-shaped organelles measuring about 2-4 μm by 4-7 μm. There are two membranes enclosing the stroma, which is the dense fluid within the chloroplast. Also, an elaborate system of interconnected thylakoid membranes segregates the stroma from the thylakoid space. Sometimes thylakoid sacs are stacked in grana; chlorophyll is in the thylakoid membranes. 4) Chloroplast’s structure enables it to separate itself from other substances in the cell by two membranes, giving it a function all its own by allowing the chloroplast to have a specific internal environment. 5) Summary equation for photosynthesis: 6CO 2 + 12H 2 O + Light energy → C 6 H 12 O 6 + 6O 2 + 6H 2 O II. The Pathways of Photosynthesis 6) Van Niel hypothesized that plants split water as a source of hydrogen, releasing oxygen as a by-product; nearly twenty years
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