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Cells and Energy • How does a cell obtain energy? • How do some cells make food molecules? Cells and Energy • cellular respiration • glycolysis • fermentation • photosynthesis All cells must have energy to function When bonds of sugars are broken energy is released There are two basic processes that release energy Cellular Respiration Fermentation What processes do cells use to bring materials in and out? All cells use Chemical Energy To stay alive cells must be able to release the chemical energy in bonds Glucose a sugar is the major source of energy for most cells Cellular Respiration Cellular respiration is a series of chemical reactions that convert the energy in food molecules into a usable form of energy called ATP. Glycolysis, the first step in cellular respiration, is a process by which glucose is broken down into smaller molecules. It occurs in the cytoplasm. Glycolysis produces some ATP molecules and uses energy from other ATP molecules. Cellular Respiration (cont.) • The second step of cellular respiration requires oxygen and the smaller molecules of glucose which move to the mitochondria of eukaryotic cells. • A chemical reaction takes place that produces: Large amounts of ATP—usable energy—, Water, and carbon dioxide. • Cells use ATP to power all cellular processes. • Aerobic reaction: requires oxygen Molecules form to release large amounts of energy which include energy that is used energy that is stored (ATP) (useable) energy that is given off as heat Reactions in the Mitochondria The chemical equation for cellular respirations: Glucose + Oxygen →Chemical Energy + Water + Carbon Dioxide C6H12O6 + 6O2 → Chemical Energy + 6H2O + 6CO2 Cellular Respiration is considered ______________because it requires oxygen It is a complex process that has two stages The first stage takes place in the cytoplasm Glucose is broken down into smaller molecules that release a small amount of energy called _____________________. The second stage takes place in the_____________. Fermentation Fermentation is a reaction that eukaryotic and prokaryotic cells use to obtain energy from food when oxygen levels are low. Fermentation occurs in a cell’s cytoplasm, not in mitochondria. Two types of fermentation Alcohol Fermentation Lactic Acid Fermentation Anaerobic:proces Fermentation s in which cells release energy without oxygen – Takes place in the cytoplasm Breaks glucose down into smaller molecules Releases a small amount of energy Alcohol fermentation -Produces alcohol and carbon dioxide -Occurs in yeasts (fungi) and plant cells -Important to bakers causes dough to rise -Important to brewers creates carbonation Occurs in animals, bacteria Lactic Acid -Bacteria convert sugar in milk to Fermentation lactic acid Used to make cheese, yogurt, sourdough bread, sauerkraut, soy sauce, miso Gives foods a slightly sour taste During prolonged exercise muscles in your body convert energy this way – it causes a burning sensation Fermentation (cont.) How does a cell obtain energy? The formula for cellular respirations is Glucose Energy + Oxygen → Chemical + Water + CarbonDioxide C6H12O6 + 6O2 → Chemical Energy + 6H2O + 6CO2 Photosynthesis and Cellular Respiration are two processes in the energy cycle These processes do not have to occur in the same cell or in the same organism Photosynthesis Photosynthesis is a series of chemical reactions that convert light energy, water, and CO2 into the food-energy molecule glucose and give off oxygen. photosynthesis from Greek photo, means “light”; and synthesis, means “composition” Photosynthesis (cont.) • The chemical reactions of photosynthesis are powered by light energy. • In the chloroplasts of plants, pigments such as chlorophyll absorb light energy • Chlorophyll absorbs all colors except green light, which is reflected as the green color in leaves. Photosynthesis (cont.) How do some cells make food molecules? Photosynthesis (cont.) • . Chloroplasts contain chlorophyll Chlorophyll is the pigment that traps the energy in sunlight – reflects green Photosynthesis takes place in the chloroplasts Photosynthesis Is a complex Process that has two stages The first stage of photosynthesis involves capturing the suns energy in the chloroplasts Chlorophyll acts as a “solar cell” to capture light energy and supply power for the second stage of photosynthesis Photosynthesis The Second stage requires the raw materials H2O (water) and CO2 (carbon dioxide) Water is provided by the roots of the plant Carbon Dioxide enters the plant through small openings on the underside of leaves called Stomata After entering the leaves H2O&CO2 move to the chloroplasts In the chloroplasts both water and carbon dioxide go through a series of chemical reactions powered by the suns energy to create oxygen and glucose The chemical formula is: 6CO2 + 6H2O + light energy → C6H12O6+6O2 Photosynthesis View the process at classzone.com http://www.classzone.com/books/ml_science_life/page_buil d.cfm?id=resour_ch2&u=1 Plants do not immediately use all of the glucose it is stored as starch and also makes cellulose Plants are considered producers or autotrophs because they can make their own food Organisms that can not make their own food are called consumers or heterotrophs • When an organism eats plant material it takes in food energy from the plant’s glucose. • An organism’s cells use the oxygen released during photosynthesis and convert the food energy into usable energy through cellular respiration • Glycolysis is the first step in cellular respiration. • Fermentation provides cells, such as muscle cells, with energy when oxygen levels are low. • Light energy powers the chemical reactions of photosynthesis. What does cellular respiration convert the energy in food molecules into? A. B. C. D. ATP glucose lactic acid carbon dioxide Eukaryotic and prokaryotic cells use fermentation to obtain energy from what? A. B. C. D. water food oxygen pigments What chemical reactions converts light energy, water, and CO2 into the foodenergy molecule glucose? A. B. C. D. lactic-acid fermentation cellular respiration alcohol fermentation photosynthesis Do you agree or disagree? 7. ATP is the only form of energy found in cells. 8. Cellular respiration occurs only in lung cells. Key Concept Summary Interactive Concept Map Chapter Review Standardized Test Practice