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CELL ENERGY All cells need energy. Energy is the capacity to move or change matter. Forms of energy important to life: chemical radiant mechanical electrical Energy can be transformed from one form to another. Energy of motion is called Kinetic Energy that is stored is Potential Laws of energy: 1. Energy may be converted from one form to another but not destroyed. 2. Some usable energy is always lost during conversion. Cells store energy in the bonds of molecules. Breaking molecular bonds is a way to get energy for cell processes like: active transport cell reproduction producing cell products movement A major energy storage molecule is glucose. Glucose may be stored as starch in plants or glycogen in animals. Energy may also be stored in the bonds of lipids and even proteins. Long term energy storage is important, but cells need lots of energy fast. The main cell compound for short term energy storage and release is ATP, Adenosine tri-phosphate composed of: a) adenine, a base b) ribose, a sugar c) phosphate, an ion Energy is stored in the phosphate bonds. Cells can use energy from the breakdown of ATP and store it in the third phosphate bond to make ATP from ADP. ATP can be sent all over the cell quickly to give energy where needed but it must be constantly regenerated. All organisms need energy. Heterotrophs get energy by “eating”. For example: animals, fungi, some bacteria, some protists are heterotrophs. Autotrophs get energy from the sun. For example: plants, algae, some bacteria some protists Only about 10% of the species on Earth are Autotrophic. Some are chemosynthetic. Converting unusable sunlight into usable chemical energy is called: Photosynthesis 6H2O + 6CO2 ―› C6H12O6 + 6O2 Chlorophyll is the chemical that can capture the energy of sunlight. Chlorophyll is found in organelles called Chloroplasts Photosynthetic cells may contain hundreds of chloroplasts. Other pigments like Carotenoids (orange) Anthocyanins (redish) Xanthophylls (yellow) can absorb light that chlorophyll can’t. There are two sets of reactions in photosynthesis 1. Light dependent 2. Calvin Cycle Light dependent reactions: Chlorophyll absorbs energy and uses it to: convert ADP to ATP ADP + P ATP break apart water to get H+ and produce O2 convert NADP+ to NADPH + + NADP + 2e + H NADPH Light dependent reactions take place on the thylakoid membranes. Calvin cycle: Reactions take place in the stroma and do not need light energy. Uses energy from ATP, + H and e from NADPH CO2 from the air to make glucose C6H12O6 Summary of photosynthesis Factors that affect the rate of photosynthesis: light intensity temperature length of daylight CO2 levels air pollution