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Cellular Respiration. Chemical Energy and Food. A Calorie (with a capital C) is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. Note: The calorie you see on a cereal box is actually a kilocalorie or 1,000 Calories. 1 Calorie = 4,184 joules.
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Chemical Energy and Food • A Calorie (with a capital C) is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. • Note: The calorie you see on a cereal box is actually a kilocalorie or 1,000 Calories. • 1 Calorie = 4,184 joules
Cellular Respiration • Cellular Respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. • Cellular Respiration Equation: • 6O2 + C6H12O6 6CO2 + 6H2O + Energy
Glycolysis • First part of cellular respiration: Glycolysis. • Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid (a 3-carbon compound) • 2 ATP molecules are needed go into glycolysis • The cell uses those two ATP and makes 4 ATP molecules and 2 NADH molecules • Therefore, a net gain of 2 ATP and 2 NADH
No oxygen? No problem… sort of • When oxygen is not present, glycolysis is followed by fermentation. • Fermentation releases energy from food molecules by producing ATP in the absence of oxygen • Fermentation is anaerobic – does not require oxygen. • Two main types: • Lactic acid fermentation • Alcoholic fermentation
Alcoholic Fermentation • Yeast uses alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes • Pyruvic acid + NADH alcohol + CO2 + NAD+ • This process makes bread rise and of course alcohol
Lactic Acid Fermentation • Lactic acid can be made from pyruvic acid in the absence of oxygen • This occurs in your muscles during rapid exercise when you’re not getting enough oxygen to your cells • Pyruvic acid + NADH Lactic acid + NAD+ • Lactic acid build up is painful = pain in muscles while working out
Lactic Acid Fermentation • Unicellular organisms going through lactic acid fermentation are used to make cheese, yogurt, buttermilk, and sour cream.
The Krebs Cycle • In the presence of oxygen (aerobic), after glycolysis, pyruvic acid goes to the Krebs Cycle (also called the Citric Acid Cycle). • During the Krebs Cycle, pyruvic acid is broken down into carbon dioxide and energy is extracted • Step 1: Pyruvic acid enters mitochondria. One carbon is wasted as carbon dioxide. Two carbons become acetyl-CoA and forms citric acid.
The Krebs Cycle • Step 2: The citric acid is broken down, more carbon dioxide is released, and electrons are transferred to electron carriers. • This carbon dioxide that is released is what you breathe out. • NAD+ and FAD (flavine adenine dinucleotide) are the electron carriers. They are converted into NADH and FADH2.
Electron Transport • Electrons from the Krebs Cycle are passed from NADH and FADH2 to the electron transport chain (ETC). • The ETC uses these electrons from the Krebs cycle to convert ADP into ATP. • Step 1: Electrons passed through carrier proteins located on membrane of mitochondria (eukaryotes) or cell membrane (prokaryotes). • Oxygen is the final electron acceptor and combines with H+ to form water.
Electron Transport • Step 2: Every time 2 electrons move down the chain, H + is moved across the membrane. • These H + ions make the membrane positive • Step 3: As the H + ions move across the membrane, ATP synthase attaches a phosphate group to ADP making ATP.
Totals of Cellular Respiration • 36 total ATP produced in presence of oxygen
Energy and Exercise • Exercise that is intense and ends quickly will utilize fermentation. • Example: 200 m dash • Body only has enough ATP for a few minutes of intense activity • Exercise that is long-lasted and steady will use cellular respiration. • Example: aerobic exercises like swimming, running, dancing. • Cell respiration generates a continuous, steady supply