Presentation on theme: "Cells Need Energy 1. Organisms obtain energy from food"— Presentation transcript:
1 Cells Need Energy 1. Organisms obtain energy from food Slide # 2Cells Need Energy1. Organisms obtain energy from food2. Glucose is main source of food for cells3. Cells break chemical bonds of glucose; energy releasedGo to Section:
2 Respiration*** We DON’T have to teach super specific processes of glycolysis, fermentation, just the reactants and products of each of those and that NADH is an electron carrier just like ATP (they are all energy molecules)
3 Cellular RespirationIf cellular respiration took place in just one step:All of the energy would be released at onceMost would be lost in the form of light and heat.Instead, a living cell has to release chemical energy in food molecules a little bit at a time.Must trap those little bits of energy by using them to make ATP.
4 Cellular RespirationCellular Respiration - Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen
5 Cellular Respiration Requires (Reactants): Gives Off (Products): GlucoseOxygenGives Off (Products):WaterCarbon DioxideEnergy
6 3 Stages of Cellular Respiration GlycolysisKrebs CycleElectron Transport ChainEach stage captures some of the chemical energy available in food molecules and uses it to produce ATP.
7 First Stage: Glycolysis Glycolysis –A molecule of glucose is broken into two molecules of pyruvic acid.Occurs in the cytoplasmDoes not require oxygen (anaerobic)1 Glucose Pyruvic AcidC-C-C-C-C-C C-C-C C-C-C
8 TO THE ELECTRON TRANSPORT CHAIN GlycolysisGlucoseC-C-C-C-C-CC-C-C C-C-C2 Pyruvic AcidC-C-C C-C-C2 ATP2 ADP2 NAD+4 ADPTO THE ELECTRON TRANSPORT CHAIN2 NADH4 ATP
9 Products of Glycolysis NET Gain 2 ATP (Major Energy molecule)2 NADH (Minor Energy molecule)2 Pyruvic Acid Molecules(Glucose – Sugar Sugar Song)
10 Fermentation Krebs Cycle GlycolysisFermentation Krebs CycleAnaerobic (no oxygen)Aerobic (oxygen)
11 Second Stage: Fermentation or Krebs Cycle Glycolysis can be followed by fermentation or the Krebs cycle depending if oxygen is present.Fermentation will occur if no oxygen is present.Krebs Cycle will occur if oxygen is present.
12 Second Stage: Fermentation Fermentation - Releases energy from food molecules by producing ATP in the absence of oxygen.Anaerobic - Does not require oxygenOccurs in the cytoplasm (cytosol)
13 Fermentation Two types of Fermentation: Alcoholic Fermentation Lactic Acid Fermentation
14 Alcoholic Fermentation Produces:Ethyl alcoholCarbon dioxideExamples:Used to produce beer and wineCauses bread dough to riseCarried out by yeasts and a few other microorganisms
15 Lactic Acid Fermentation Produces:Lactic AcidExamples:Produced in your muscles during rapid exerciseBuildup of lactic acid causes a painful, burning sensation…why muscles feel soreUsed in production of cheese, sour cream, yogurt, and pickles.Carried out by animals and some unicellular prokaryotes (bacteria).
16 At the End of Glycolysis 90% of the chemical energy that was available in glucose is still unusedLocked in the high-energy electrons of pyruvic acidOxygen is required for the final steps of cellular respiration.Oxygen is the world's most powerful electron acceptor.Therefore, cellular respiration is aerobic (requires oxygen).
17 Second Stage: Krebs Cycle Krebs Cycle - Pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions.Occurs in the mitochondrion.
18 Krebs Cycle Starts: Pyruvic Acid Produces: Carbon Dioxide Source of all the carbon dioxide in your breath.Energy Tally - Each Molecule of Pyruvic Acid Produces:1 ATP (and NADH/FADH2)All energy molecules!
19 Third Stage: Electron Transport Chain The electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP into ATP.Oxygen serves as the final electron acceptor.Occurs in the mitochondrion.
20 ATP Glycolysis: 2 ATP molecules per glucose molecule Needs 2 ATP (Investment)Produces 4 ATPNet gain of 2 ATP molecules.Krebs Cycle and Electron Transport: 34 ATP molecules per glucose moleculeTotal = 36 ATP
22 Exercise: Quick Energy Muscles only contain enough ATP for a few seconds of intense activityThen, muscle cells produce their ATP by lactic acid fermentation.Lasts only about 90 seconds or about meters.Produces lactic acid, which requires oxygen debt (must repay after the race with plenty of heavy breathing).
23 Exercise: Long-Term Energy (Longer than 90 seconds) Cellular Respiration is the only way to generate a continuing supply of ATPReleases energy slowly (why athletes must pace themselves)Body stores energy in muscle and other tissues in the form of the carbohydrate glycogen (usually enough to last for min.)After that, your body begins to break down other stored molecules, including fats, for energy
24 Photosynthesis vs. Respiration Photosynthesis and cellular respiration take place in opposite directions!Photosynthesis: Use light energy to build a sugar.carbon dioxide + water + light energy → sugars + oxygenRespiration: Break down sugar to release energy.oxygen + sugars → carbon dioxide + water + energy
25 Respiration: Break Down Glucose Photosynthesis: Build Glucose