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Where does the Alcohol in Beer come from or… How do Cells Obtain Energy? •What is Energy? •The Role of Oxygen and Enzymes •Cellular Respiration –Glycolysis –Krebs Cycle –Electron Transport Chain What is Energy? • Energy is the term used to denote anything that can do work • Energy can take different forms (light, heat, movement) • Energy can be converted from one form to another The Role of Oxygen • Connection between breathing & life is an ancient one – Exchange of gases is part of what it means to be alive & – Outward sign of metabolism – Joseph Priestly experiment – Postulated that poisonous phlogiston is PRODUCED. 1 The Role of Oxygen • Antoine Lavoisier – Found that it is oxygen from air that is CONSUMED – In a fire, Organic Molecules combine with Oxygen (O 2) in the air to form CO2 & H2O – he called the process OXIDATION – Oxidation also occurs when organisms metabolize food Chemical Reactions in Non-living vs. Living Organisms •Lower temperature for reactions •Reactions can be highly Regulated ENZYMES make Chemical Reactions Possible inside CELLS 2 ENZYMES are Proteins Enzymes •L o w T e m p s •S p e c i f i c •H a r n e s s E Cellular Respiration – The name given to metabolic pathways in which Cells harvest the energy from the metabolism of food molecules Food is Broken Down ATP is Produced 3 ATP Cycle - ATP is the Common Currency for Energy Transfer in Cells - ATP is used to fuel Biological Work Glucose → → CO2+ H2O Amino → → Proteins Acids Cellular Respiration Glucose breakdown is one of the main pathways by which cells obtain ATP 1. Glycolysis 2. Krebs Cycle 3. Electron Transport The production of Beer relies on Cellular Respiration in YEAST Cells Magnified Yeast Cells 4 Beer Production Requires …. •Germinating Barley Seeds Barley Seeds contain chains of GLUCOSE molecules in …… Beer Production Requires…. •Germinating Barley Seeds •Enzymes that can breakdown these chains into individual GLUCOSE molecules This mixture is MALT YEAST cells are added to the malt They begin to grow using the glucose as an energy source 5 Glycolysis • Universal energy-harvesting process of life, very primitive – Evolved early in life’s history – Means “sugar-splitting” • 6-C sugar glucose is split in half to • Make two 3-C compounds Glycolysis converts sugars to Pyruvic Acid + ATP + NADH C-C-C-C-C-C → 2(C-C-C) NAD+ → → NADH NADH is a KEY product in Cellular Respiration Glycolysis Uses NO oxygen -An ANaerobic process (…. one not requiring oxygen) 6 Krebs Cycle Completes the breakdown of Pyruvic Acid (from Glucose) to Carbon Dioxide (CO2) and Water (H2O) -This process is Aerobic (requires oxygen) The Krebs Cycle occurs in the Mitochondria of Cells The Krebs Cycle occurs in the Mitochondria of Cells •Pyruvate ( C- C-C ) is OXIDIZED to 3 CO2 •In the process ATP & NADH are produced 7 NADH from Glycolysis & the Krebs Cycle must be RECYCLED to NAD+ If Oxygen is present è NADH is recycled by ELECTRON TRANSPORT Occurs in the Mitochondria Additional ATP is produced Electron Transport Glucose + NAD+ NADH - from glycolysis 2 The production of Beer relies on Cellular Respiration in YEAST Cells using MALT Magnified Yeast Cells 8 The Malt/Yeast mixture is kept in large VATS -BUT the Yeast eventually uses up all it’s OXYGEN - NOW under Anaerobic conditions yeast can still obtain Energy from Glucose by a process known as FERMENTATION FERMENTATION • NADH is in LIMITED Supply in cells and must be RECYCLED NO OXYGEN NAD+ → → NADH X Fermentation • Yeast can recycle NADH by first Converting Pyruvic Acid to Acetaldehyde è Acetaldehyde C-C-C-C-C-C è è 2(C-C-C) è 2(C-C)+ CO2 NAD+ è è NADH 9 Fermentation • And then converting Acetaldehyde to ETHANOL è Acetaldehyde è ETHANOL C-C-C-C-C-C è è 2(C-C-C) è è 2(C-C)+ CO2 NAD+ è è NADH NADH è è NAD+ Alcohol and CO2 are the Final Products of Fermentation Pyruvic Acid è Acetaldehyde è Ethanol + CO2 10