Light-Dependent Reactions of Photosynthesis in

Chloroplasts Extracts of Spinach Leaves.

Photosynthesis is the process that converts energy in sunlight to chemical forms of energy that can be used by biological systems (Figure 1). Many different organisms, ranging from plants to bacteria, carry out photosynthesis. The photosynthetic process in plants and algae occurs in small organelles known as chloroplasts that are located inside cells. The photosynthetic reactions are traditionally divided into two stages - the "light reactions," which consist of electron and proton transfer reactions and the "dark reactions," which consist of the biosynthesis of carbohydrates from carbon dioxide. The light reactions occur in a complex membrane system that is made up of protein complexes, electron carriers, and lipid molecules. The photosynthetic membrane is surrounded by water and can be thought of as a two-dimensional surface that defines a closed space, with an inner and outer water phase. A molecule or ion must pass through the photosynthetic membrane to go from the inner !

space to the outer space (Stern 2000). The protein complexes embedded in the photosynthetic membrane

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First, we acquired six cuvettes. The cuvettes were marked 0-5. We then filled the cuvettes with the appropriate amount of solution (see Table 1). The "0" test tube is used to recalibrate the photospectrometer every five minute to prevent error. The photosprectrometer is an electronic device that emitted a ray of light through the contents of the cuvette and measure the amount of light makes it through the solution thus making an accurate measurement of the light absorbed by the color. After the cuvettes were filled with the solution they were covered with Para film and agitated. Cuvette "2" was covered in foil to demonstrate the dark reaction. Cuvettes 1,4,and 5 were placed in high light exposure areas and cuvette 3 was placed in normal lighting conditions. At five-minute intervals the cuvettes were wiped off, put into the spectrophotometer, and the results were recorded. This procedure was performed every five minutes for thirty minutes.

have a unique orientation with respect to the inner and outer phase. The asymmetrical arrangement of the protein complexes allows some of the energy released during electron transport to create an electrochemical gradient of protons across the photosynthetic membrane. Photosynthetic electron transport consists of a series of individual electron transfer steps from one electron carrier to another. The electron carriers are metal ion compl

Some common words found in the essay are:
Introduction Photosynthesis, Results Cuvette, Hill Reaction, Materials Methods, Robin Hill, O2 Inaccuracies, NADP+ NADPH, NADPH NADH, Plant Biology, photosynthetic process, photosynthetic membrane, stern 2000, Stern KR, electron transport, protein complexes, electron carriers, cuvette 4, reactions consist, amount light, five-minute intervals,
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