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Cellular Respiration. CONVERTS ENERGY IN FOOD TO ENERGY IN ATP. CELLULAR RESPIRATION INVOLVES SEVERAL STEPS. Involves over 25 chemical reactions Occurs in cytoplasm and mitochondria Can be divided into three main stages : 1) Glycolysis 2) The Krebs cycle
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Cellular Respiration CONVERTS ENERGY IN FOOD TO ENERGY IN ATP
CELLULAR RESPIRATION INVOLVES SEVERAL STEPS • Involves over 25 chemical reactions • Occurs in cytoplasm and mitochondria • Can be divided into three main stages: • 1) Glycolysis • 2) The Krebs cycle • 3) The electron transport chain
STAGES OF CELLULAR RESPIRATION • 1st Stage: Glycolysis - cytoplasm—anaerobic (no O2 needed) • 2nd Stage: Krebs Cycle - mitochondria—aerobic (O2 needed) • 3rd Stage: Electron Transport Chain - mitochondria—aerobic (O2 needed)
STAGE ONE: GLYCOLYSIS • Does NOT require oxygen anaerobic • First step in cellular respiration • Occurs in cytoplasm • Occurs in ALL organisms • One glucose molecule is split to form two molecules of pyruvic acid
GLYCOLYSIS HAS 2 PHASES • Energy investment phase: 2 ATP needed to start reaction • Energy harvest phase: 4 ATP produced • Net gain: 2 ATP
Envelope has inner and outer membranes Inner membrane: Very highly folded provides increased surface area Has many sites where cellular respiration can occur Encloses thick fluid matrix STRUCTURE OF MITOCHONDRIA
STAGE TWO: THE KREBS CYCLE • Occurs in matrix of inner mitochondrial membrane • Aerobic – O2 needed • 2 Pyruvic acid 2 Acetyl CoA + 2 CO2 • 2 Acetyl CoA 4 CO2 + 2 ATP • Net result: 2 ATP produced
STAGE THREE: ELECTRON TRANSPORT CHAIN • Occurs on inner mitochondrial membrane • Also called oxidative phosphorylation or chemiosmosis • Aerobic—requires O2 • Electron transport chain works with H+ ions and ATPsynthase (proteins in membrane) to produce ATP • Generates up to 34 ATP per original glucose molecule
MAXIMUM ATP PER GLUCOSE • GLYCOLYSIS = 2 ATP • KREBS CYCLE = 2 ATP • ELECTRON TRANSPORT CHAIN / ATP SYNTHASE = 34 ATP 38 ATP This production results only if O2 is present
FERMENTATION • Process that makes ATP without O2 • ATP produced in fermentation comes entirely from glycolysis • Produces no additional ATP • When O2 is not present there is an overall net gain of 2 ATP per glucose molecule • Two major types of fermentation: • Lactic acid fermentation • Alcoholic fermentation
LACTIC ACID FERMENTATION • Occurs in muscle cells when O2 supply is too low • Cellular respiration continues but fermentation is main ATP source • Produces lactic acid - waste product • Results in muscle soreness after strenuous exercise • Relieved after O2 supply restored
LACTIC ACID FERMENTATION Causes muscle pain and cramping
ALCOHOLIC FERMENTATION • Yeast: alcoholic fermentation • Produces ethyl alcohol instead of lactic acid under anaerobic conditions • Used in brewing industry • Released CO2 makes champagne and beer bubbly • Used by bakers to make bread rise
FERMENTATION IN MICROORGANISMS • Fungi & Bacteria: produce lactic acid like muscle cells • Used to flavor yogurt, some cheeses • Other fermentation processes: • Soybeans soy sauce • Cabbage sauerkraut
