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Chapter 7 Biochemical Pathways used to Harvest Energy in animals AKA - Cellular Respiration When you eat, how does the energy in your food change into a form your body can use? It uses a biochemical pathway to break down the food molecules into ATP Biochemical Pathway: - Chemical reaction (in a living organism) where the products of 1 reaction are the reactants in the next. Pathway 2: Cellular Respiration Main purpose: convert glucose into ATP - occurs in all living things (including plants) - happens in the mitochondria Formula for Cellular Respiration: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP Cellular Respiration: Step One Glycolysis: -Break down of glucose (C6H12O6), a 6-carbon sugar, into 2 smaller, 3-carbon sugars - it's universal; all living organisms start with this step -produces NADH, used to make ATP Cellular Respiration: Step Two - depends on whether oxygen is present or absent Glucose Glycolysis O2 present Aerobic Respiration O2 absent Alcoholic Fermentation (bacteria & yeast) Lactic Acid Fermentation (humans & animals) Anaerobic respiration: - forming ATP without oxygen - less efficient than aerobic respiration - only makes 2 ATP molecules for every glucose 2 types: 1. Alcoholic fermentation 2.Lactic Acid Fermentation Anaerobic respiration produces lactic acid or alcohol without oxygen Anaerobic Respiration cont... Alcohol Fermentation: - glycolysis products are converted into: *alcohol (ethanol) * CO2 * 2 ATP - used by bacteria & fungi * Brewers of alcohol use yeast (fungus) & sugar source for fermentation Anaerobic respiration cont.... Lactic Acid Fermentation: - happens in animals & humans when oxygen is used faster than it is taken in - products of glycolysis are converted into: * lactic acid * CO2 * 2 ATP Lactic Acid Fermentation – No oxygen needed Q: I'm a runner and I ran a marathon yesterday, why am I so sore today? A: Build up of lactic acid makes you sore & have muscle cramps. Q: If lactic acid fermentation can produce ATP without using oxygen, then why do people die from lack of oxygen in such a short time? A: L.A. Fermentation doesn't happen in nerve cells so brain needs constant supply of O2 to run things Aerobic Respiration: - 3 step process that uses oxygen to produce ATP - much more efficient than anaerobic respiration - makes ~ 36 ATP molecules from every glucose molecule Aerobic Respiration cont... Step 1: Glycolysis - breaking glucose into 2 3-carbon sugars, 2 (net) ATP & 2 NADH Step 2: Kreb's Cycle - 5 step circular pathway that produces: * 6 CO2 * 8 NADH and 2 FADH2 (molecules that “ hold” energy) * 2 ATP Kreb's Cycle Step 3: Electron Transport Chain - produce ATP when NADH and FADH2 release their electrons to Oxygen - Each oxygen accepts 2 electrons and 2 H+ ions to form ..... H2O - waste products: H2O and CO2 - energy trapped: 32 ATP Produces 32 ATP So what do a burning match and a burning marshmallow have in common with aerobic respiration?