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Cellular Respiration Chapter 4.2 Objectives • Describe Metabolism • Describe the role of ATP and how it functions • Understand what goes on during the three stages of aerobic cellular respiration that lead to the production of ATP: glycolysis, Krebs cycle, and the electron transport chain • Recognize and explain the summary equation for aerobic cellular respiration Objectives continued • Describe the location and structure of mitochondria. Understand its function in cellular respiration • Summarize the reactions of glycolysis (what goes on) • Describe the role of Oxygen in the electron transport chain • Be able to describe fermentation • Recognize that multiple energy sources can “fuel” cellular respiration Metabolism • The sum of all the chemical processes occurring in an organism at one time • Concerned with the management of material and energy resources within the cell • Reactions can break down big molecules into smaller units or build larger molecules from smaller components Anabolic (Biosynthetic) Pathways • Pathways that consume energy to build larger, complicated molecules from simpler ones • Polymerization • Photosynthesis 6CO2 +6H20 + light C6H1206 + 6O2 • Carbon dioxide, a low energy molecule, gets converted into carbohydrate, a high energy molecule Catabolic Pathways • Pathways that release energy by breaking down complex molecules into simpler compounds • Cellular respiration • C6H1206 + 6O26CO2 +6H20 + ENERGY • Carbohydrate, a high energy molecule, gets “digested” into carbon dioxide, a low energy molecule • Cells use released energy to make ATP ATP Nucleotide with three phosphate groups attached to the ribose sugar • Energy molecule used to shuttle energy between catabolic and anabolic reactions • Energy is released from ATP through the loss of phosphate groups ATP • Energy is released from ATP through the loss of phosphate groups Phosphorylation • When ATP gives a phosphate group to another molecule it is called phosphorylation • Phosphorylated molecules have “more” energy and can do the work of the cell • How do we make ATP? Cellular Respiration What is cellular respiration? Cellular Respiration : the making of ATP through the breakdown of foods • Aerobic Cellular Respiration • Fermentation Three Stages of Aerobic Cellular Respiration C6H1206 + 6O26CO2 +6H20 + ENERGY • Aerobic cellular respiration has 4 steps – Glycolysis • in cytosol – Kreb’s cycle • in mitochondrial matrix – Electron Transport Chain • at inner membrane of mitochondria Structure of the Mitochondria • Organelle with an outer and inner membrane • The Krebs cycle takes place in the matrix of the mitochondria – space bordered by the inner membrane • Electron Transport Chain takes place across the inner membrane – between the matrix and intermembrane space This organelle produces the majority of ATP for the cell. Glycolysis • This part of cellular respiration takes place in the cell cytoplasm • Each Glucose molecule gets converted into 2 pyruvate molecules • Energy requiring and energy releasing steps • Energy net yield is 2 ATP and 2 NADH • Enzymes help along the way Krebs Cycle • Each pyruvate (carbohydrate) molecule is completely oxidized into carbon dioxide • Energy released from these reactions results in the formation of 1 ATP molecule but 3 NADH molecules Collectively, 2 ATP and 6 NADH are made from the 2 pyruvates. NADH will be used in the electron transport chain. Electron Transport Chain Uses NADH • During the electron transport chain, H+ is moved against a gradient. • The energy needed to do this is supplied by electrons carried by NADH What happens along the inner membrane of the mitochondria? • The loss of electrons from NADH result in the addition of energy to protein pumps in the memebrane resulting in a H+ being moved from the inside to the outside of the inner membrane • This happens many times creating an imbalance Oxygen pulls electrons to (gradient) of H+. keep them moving. What happens along the inner membrane of the mitochondria? • ATP is made as H+ ions are allowed back into the matrix of the mitochondria by a different protein (ATP synthase). • The energy released by the “rush” of H+ is used by this enzyme to make ATP (kind of like a rush of water in a Ultimately, aerobic respiration stream being used to turn a produces ~36 ATP molecules water wheel). from each individual glucose molecule. Why do we need oxygen? • Oxygen is required by any organism that has mitochondria because it is used to keep the Electron Transport Chain running • Oxygen pulls of electrons from the chain and combines with 2 H+ to form H20 What if we did not have oxygen? • Without trees and bacteria to make oxygen, we would still be able to make ATP from sugar (just not as much) • Modifications of glycolysis called fermentation reactions are used to release energy Fermentation Reactions • These reactions produce only 2 ATP per glucose molecule and must regenerate NAD+ resulting in the formation of either: 1 Ethanol and CO2 or 2 Lactic Acid . What about other foods? • Proteins, Carbs and Fats can all be utilized for energy following hydrolysis • Amino Acids are converted to intermediates including pyruvate, 2-, and 4-carbon molecules • Carbs enter glycolysis at the beginning or in the middle • Fats components – glycerol enters as 3-carbon molecule – Fatty acids enter as 2-Carbon molecules