CHAPTER 7: CELLULAR RESPIRATION ïƒ 7-1: Glycolysis + Fermentation ïƒ 7-2: Aerobic Respiration

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  • CHAPTER 7: CELLULAR RESPIRATION7-1: Glycolysis + Fermentation7-2: Aerobic Respiration

  • Cellular RespirationMost foods contain usable energy, stored in complex organic compounds such as:ProteinsCarbohydratesFatsAll cells break down organic compounds into simpler molecules, a process that releases energy to power cellular activities

  • Harvesting Chemical EnergyCellular RespirationComplex process in which cells make ATP by breaking down organic compoundsBoth autotrophs + heterotrophs undergo cell respirationSome of the energy is used to make ATP; then energy used by cells to do work

  • Overview of Cellular RespirationBiochemical pathway with PhotosynthesisProducts + ReactantsRedox reactions (OILRIG: e- = energy)EquationC6H12O6 + 6 O26 CO2 + 6 H2O + NRGTwo Stages:GlycolysisAerobic Respiration

  • Glycolysis Biochemical pathway in which one 6-C molecule of glucose is oxidized to produce two 3-C molecules of pyruvic acidCatalyzed by specific enzymesReactions occur within cytosol of cellsAnaerobic process

  • 4 Major Steps of GlycolysisTwo phosphate groups are attached to one molecule of glucose, forming a new 6-C compound. ATP supplies the phosphate groupsThe 6-C compound splits into 2 3-C compounds called G3P

  • Glycolysis (cont.)The 2 G3P molecules are oxidized and each receives a phosphate group creating two new 3-C compounds. During the oxidation, NAD+ picks up electrons lost by the oxidation of each G3P compound (redox) - NADHAll phosphate groups are removed which makes 2 new 3-C compounds called pyruvic acid. Each phosphate groups is added to ADP to make four molecules of ATP

  • Net Yield of NRG?Glycolysis only produces 2 ATP molecules to be used by the cell from one molecule of glucose

    *Even though 4 ATP are produced at Step 4, 2 ATP were used in Step 1*

  • Recap of Glycolysis

  • Video RecapGlycolysis

  • FermentationIf oxygen is present after glycolysis, pyruvic acid enters Aerobic RespirationIn anaerobic conditions, some cells can convert pyruvic acid into other compounds through additional biochemical pathwaysGlycolysis + additional pathways = FermentationTakes place in the cytosol of cellsDoes not produce any ATPHelps regenerate NAD+, which is used throughout cellular respirationDiffers in enzymes used and compounds madeTwo most common: Lactic Acid + Alcoholic

  • Lactic Acid FermentationPyruvic acid converted into lactic acidL.A.F. involves the transfer of one H atom and one free proton (H+)In the process, NAD+ is regenerated and can be used again in glycolysis

  • Lactic Acid Fermentation

  • L.A.F. (cont.)L.A.F. used by microorganisms in manufacturing dairy products such as yogurt and cheese

  • L.A.F. (cont.)L.A.F. also occurs in your muscle during strenuous exerciseDuring this type of exercise, muscle cells use up O2 much more quickly than it can be delivered to themAs O2 depletes, aerobic respiration is changed to L.A.F.The cytosol more acidic and muscles become fatigued or soreEventually lactic acid gets converted back to pyruvic acid by the liver

  • Alcoholic FermentationPyruvic acid converted into ethyl alcohol + CO2

  • Alc. Fermentation (cont.)A CO2 molecule is removed from pyruvic acid, leaving a 2-C compoundTwo Hydrogen atoms are added to the 2-C compound to form ethyl alcohol (ethanol)H atoms transferred from NADH and H+, regenerating NAD+ for use in glycolysis

  • Alc. Fermentation (cont.)

  • Alc. Fermentation (cont.)AF by yeast cells to make beer + wineThese microorganisms eat the SUGAR in fruit or grains which cause fermentation to take placeAF also used in making bread. Rises due to loss of CO2

  • Fermentation (anaerobic pathways)

  • Efficiency of GlycolysisGlycolysis alone is only 2% efficient at extracting energy from glucoseSo where is the rest of the energy?PYRUVIC ACID!!!!!!!Early Earth + Glycolysis?Some early unicellular organisms, such as bacteria, might have been able to survive on using glycolysis for energy productionMost organisms need more energy (>2 ATP), so they needed to find a better energy-producing mechanismAEROBIC RESPIRATION!!!