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Cellular Respiration Energy For Cells
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Energy Energy – capacity to perform work Kinetic energy – energy of motion Potential energy – stored energy Conservation of energy – energy cannot be created nor destroyed Energy is converted to heat Chemical energy – form of potential energy
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Food Calories calorie – amount of energy that raises the temperature of 1 g of water by 1°C Kilocalorie – 1000 calories (these are the calories that appear on food labels)
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ATP Energy is released by breaking the bonds of food molecules (such as glucose) to make ATP from ADP ATP = adenosine triphosphate ADP = adenosine diphosphate ADP + P i → ATP
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ATP Cycle – energy coupling
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Aerobic Respiration Respiration that requires oxygen Starts in the cytoplasm glycolysis Moves to the mitochondria Krebs Cycle Electron Transport Chain
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Aerobic Respiration C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O 38 ATP are produced per molecule of glucose 2 ATP are used, so net ATP is 36 Some energy is lost as heat, so the actual number will be lower Exergonic reaction – energy is released
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Stage 1: Glycolysis “splitting of sugar” 6-C glucose broken down into two 3-C molecules (pyruvic acid)
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Stage 2: The Krebs Cycle Named for Hans Krebs (1930s) Pyruvic acid must first be converted to aceytl-CoA (acetic acid – 2-C compound – bonded to coenzyme A) Acetic acid molecules then broken all the way down to CO 2 Produces ATP and NADH & FADH 2, which will be converted to ATP later
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Stage 2: The Krebs Cycle cont.
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Stage 3: Electron Transport Chain Inner membrane of mitochondria H+ are pumped to the outside of the membrane creating potential energy ATP synthase uses energy from the movement of the H+ back inside to attach phosphate groups to ADP to make ATP
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Stage 3: Electron Transport Chain
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Anaerobic Respiration Takes place in the absence of oxygen Fewer ATP are produced – net ATP is 2 2 types Lactic acid fermentation Alcoholic fermentation
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Lactic Acid Fermentation Enzymes break down a glucose molecule into two lactic acid molecules, transferring energy to ATP C 6 H 12 O 6 + 4ADP + 4P i lactic acid + 4ATP Heavy breathing after activity needed to replenish oxygen
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Lactic Acid Fermentation
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Alcoholic Fermentation Enzymes break down a glucose molecule into two molecules of ethyl alcohol and two molecules of CO 2, transferring energy to ATP C 6 H 12 O 6 + 4ADP + 4P i 2 ethanol + 2CO 2 + 4ATP This process is used… to produce alcohol in gasoline additives baking
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Alcoholic Fermentation
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Anaerobes vs. Aerobes Facultative anaerobe – organism (such as yeast) that can obtain energy b either respiration or fermentation Obligate anaerobes – organisms that are poisoned by oxygen (cannot perform respiration) Obligate aerobes – need oxygen and cellular respiration to live
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Photosynthesis vs. Respiration
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