Photosynthesis What do you know about Photosynthesis? Key concept:plants (and some other types of organisms) are able to use light energy from the sun to produce food. Autotroph: organisms, such as plants, that can make their own food. Heterotroph: organisms, such as animals, that cannot use the sun’s energy to make their own food. They get their energy from the food that they consume. Food Chains: sun -> plant -> cow -> People Chemical Energy and ATP Energy comes in many forms: heat, light, electricity AND in chemical compounds too!!!! Human’s main fuel is not glucose, it is ATP (Adenine Tri-Phosphate) ONe of the MAIN chemical compounds that cells use to STORE and RELEASE energy is ATP (Adenosine Triphosphate) ADP + Phosphate ---> ATP ATP ---> ADP + Phosphate + energy The energy to convert ADP to ATP comes from using glucose ATP is such a useful molecule for transferring energy but NOT storing it!!! Cells only have enough ATP to last then a few seconds!!! A single molecule of the sugar glucose stores 90 times the chemical energy of ATP! Cells can store energy in this way long term. Photosynthesis Photosynthesis Equation 6CO2 + 6H2O ---> C6H12O6 + 6O2 carbon Dioxide + water ---> sugar (glucose) + oxygen Light and Pigments see diagram: pg. 207 (figure 8-5) Chlorophyll absorbs light well in the Blue-violet and red regions of the visible spectrum. But.... It does not absorb light well in the green region of the spectrum. When a pigment absorbs the light it also absorbs the energy in the light. If it does not absorb the light, it reflects it and that is why leaves appear green. The Reactions Of Photosynthesis 2 separate reactions occur during the process of Photosynthesis: Light Dependent Reactions -Require light -occur within the thylakoid membranes 2.Calvin Cycle (light independent reaction) -do NOT require light -occur within the stoma Electron Carriers: Electron Transport Chain When sunlight excites electrons in chlorophyll, the electrons gain a great deal of energy!! They are excited!!!! Think of an electron as being a “red hot coal” YOu wouldn’t pick with bare hands, you would need a “carrier” to transport it. Carrier Molecule- is a compound that can accept a pair of high energy electrons and a hydrogen ion (H+) and transfer then along with most of their energy to another molecule. This process is known as the ELECTRON TRANSPORT TRAIN!!!! The carrier molecule important in the light reactions is NADP+ (nicotinamide adenine dinucleotide phosphate) NADP+ accepts and hold the 2 high energy electrons along with a H+ ion. This converts NADP+ to NADPH. That is one way that some of the sunlight energy can be trapped in a chemical form. PHOTOSYNTHESIS: Part 1: The Light Dependent Reactions (requires light) When the Light Dependent reaction is complete the following will have occurred : Oxygen Gas is produced The electron carrier NADPH is formed Production of ATP The light dependent reactions occur inside the thylakoid membranes Part 2 Calvin Cycle OCCURS IN THE STROMA -ATP and NADPH formed in the light defendant reactions are used to make high energy sugars. -The calvin Cycle uses six molecules of CO2 to produce a 1 6-carbon sugar. -The Calvin Cycle works steadily to remove carbon dioxide from the air and turn it back into energy rich sugar. -The plant uses the sugars to meet its energy requirements and other organisms eat plants to obtained energy. Raw materials: CO2, ATP and NADPH Products: 6 carbon sugar (glucose) Thinking Visually: Construct a flow chart that illustrates the steps of photosynthesis. Begin with the energy of sunlight and end with the production of sugar. Include as much detail as possible in the numerous steps.
Posted on: Sun, 20 Oct 2013 23:00:41 +0000
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