2 Chemical Energy and Food 1 gram of sugar (glucose) when burned in the presence of O2 releases 3811 calories of heat.Calorie: the amount of energy needed to raise the temp of 1 gram of water 1 degree C.Cells gradually release energy from glucose and other compounds = glycolysis.Glycolysis releases a small amount of energy at a time.
3 Overview Glycolysis Presence of Oxygen (Cellular Respiration)Krebs CycleElectron Transport ChainNot in the Presence of Oxygen (Fermentation)Alcoholic FermentationLactic Acid Fermentation
4 Cellular RespirationCellular Respiration: the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.6O2 + C6H12O6 6CO2 + 6H2O + energyTo avoid the energy from getting burned up all at once, the release of energy in respiration happens a little at a time in 3 steps:1. glycolysis2. Krebs Cycle3. electron transport chain
5 GlycolysisGlycolysis: the process in which one molecule of glucose (C6H12O6) is broken in half, producing 2 molecules of pyruvic acid (a 3-carbon compound). Takes place in the cytoplasm of the cell.A. ATP Production-2 ATP are used to make 4 ATP molecules; net gain is 2 ATP.B. NADH Production-4 high-energy electrons added to NAD+ NADH (electron carrier).After pyruvic acid is formed through glycolysis, what happens next will depend upon whether or not oxygen is present or not.oxygen present Krebs Cycle, electron transportno oxygen fermentation (alcoholic or lactic acid)
6 Krebs Cycle (citric acid cycle) Needs oxygen; occurs in mitochondrion.The pyruvic acid (3 carbon compounds) from glycolysis is broken down into carbon dioxide in a series of energy-extracting reactions.A. Pyruvic acid enters the mitochondrion.One carbon goes off to make CO2 and isreleased into the air. The other 2 areadded to a 4-C compound to make a 6carbon molecule called citric acid.
7 Krebs (con’t) 2 carbons break off citric acid (6-C compound) and released to atmosphere.Two C then get added back to make a 6-Ccompound again. Cycle starts again.NAD and FAD are electron carriers that accept high-energy electrons = NADH & FADH. They are used to generate huge amounts of ATP.
8 Electron TransportThe electron transport chain uses the high-energy electrons from the Krebs Cycle to convert ADP to ATP.
9 FermentationOccurs after glycolysis if there is no oxygen (anaerobic).The 2 main types of fermentation are alcoholic and lactic acid.
10 Alcoholic Fermentation Pyruvic acid + NADH alcohol + CO2 + NAD+Occurs in yeast and a few other microorganisms.Most common example is when yeast is added to dough. The CO2 is released and causes the dough to rise.
11 Lactic Acid Fermentation Pyruvic acid + NADH lactic acid + NAD+In many cells, the pyruvic acid that accumulates as a result of glycolysis gets converted to lactic acid.Lactic acid is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to your tissues.As you exercise and lose oxygen in your muscles, your body will try to make ATP through lactic acid fermentation and as a result, the lactic acid builds up in your muscles and makes them ache/burn.
12 (Krebs, Electron Transport) TotalsGlycolysisOxygen- Respiration(Krebs, Electron Transport)36 ATPGlycolysisNo Oxygen(Fermentation)2 ATP