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Respiration To be able to explain • The biochemistry of aerobic respiration to show that glycolysis involves the oxidation of glucose to pyruvate • That pyruvate combines with coenzyme A to produce acetylcoenzyme A Aerobic Respiration Define the following: • • • • Respiration Breathing Aerobic respiration Anaerobic respiration Aerobic Respiration Respiration is the process that releases energy in organic molecules such as sugars and lipids. Respiration takes place in all cells all of the time Breathing is the mechanical process that supplies oxygen to the body for respiration and that removes carbon dioxide produced. Breathing ventilates the gas exchange surfaces. Aerobic Respiration is respiration with oxygen – most organisms respire aerobically releasing a relatively large amount of energy. Anaerobic respiration is respiration without oxygen – some organisms mainly bacteria can only respire anaerobically others can switch to anaerobic when oxygen levels are low. Aerobic Respiration Aerobic respiration describes the cell processes that require oxygen to release energy from all organic molecules. Respiration involves the breakdown of many molecules from the food we eat. Humans respire mainly sugars but also some amino acids and fatty acids. Aerobic Respiration • For any chemical reaction to occur energy is required to break bonds. • The process of forming new bond can either require energy or release energy • For there to be a release of energy the products of respiration must be at a lower energy level than the reactants. Aerobic Respiration Energy in molecules Glucose and oxygen CO2 +H2O Time Aerobic Respiration • What is the basic equation for respiration? • C6H12O6 + 6O2 6CO2 + 6H20 + ENERGY • In reality cell respiration takes place in a series of stages , these can produce a up to 36 molecules of ATP per molecule of glucose • The steps involved in respiration rely on a series of redox reactions • C6H12O6 + 6O2 6CO2 + 6H20 + 36 ATP Aerobic Respiration The process of aerobic respiration can be divided into 4 distinct processes: • • • • Glycolysis Pyruvate Oxidation The Krebs cycle The electron transport chain Mitochondria What are mitochondria? Mitochondria are membrane-enclosed organelles distributed through the cytosol of most eukaryotic cells. Their main function is the conversion of the potential energy of food molecules into ATP. Mitochondria have: •an outer membrane that encloses the entire structure •an inner membrane that encloses a fluid-filled matrix •between the two is the intermembrane space the inner membrane is elaborately folded with shelflike cristae projecting into the matrix. •a small number (some 5–10) circular molecules of DNA Mitochondria Aerobic Respiration Use the information on pages 11 and 12 to complete the table Stage Site Within Cell Overall process Number of ATP molecules produced Aerobic Respiration Stage Site Within Cell Overall process Number of ATP molecules produced Glycolysis Cytosol Glucose is split into 2 molecules of pyruvate 2 per glucose molecule Pyruvate Oxidation Matrix – inner fluid of mitochondria Pyruvate is converted to none acetyl co A Krebs Cycle Electron Transport Chain Acetyl co A drives a cycle of reactions to produce hydrogen 2 per turn so 4 per glucose Inner membrane Hydrogen drives a Up to 32 of mitochondria series of redox reactions per to produce ATP glucose Four stages of aerobic respiration • • • • Glycolysis The link reaction Krebs cycle Electron transport chain Glossary • Phosphorylation • the addition of phosphate groups to a molecule. • Glycolysis • the ‘splitting’ of glucose. • NAD • nicotinamide adenine dinucleotide • coA • coenzyme A • acetyl coA • acetylcoenzyme A • TCA • tricarboxylic acid • FAD • flavin adenine dinucleotide Glycolysis Glycolysis is a series of biochemical reactions by which a molecule of glucose is oxidised to two molecules of pyruvic acid. Glycolysis serves two principal functions: generation of high-energy molecules (ATP and NADH), and production of a variety of six- or three-carbon intermediate metabolites. Glycolysis is one of the most universal metabolic processes known, and occurs (with variations) in many types of cells in nearly all types of organisms. glucose Glycolysis phosphorylation 2ATP 2P 2ADP Glucose phosphate (6C) glucose Glycolysis phosphorylation 2ATP 2P 2ADP Glucose phosphate (6C) triose phosphate (3C) triose phosphate (3C) glycerate-3phosphate glycerate-3phosphate glucose Glycolysis phosphorylation 2ATP 2P 2ADP Glucose phosphate triose phosphate glycerate-3-phosphate 2NAD+ H 2NADH + H+ pyruvate triose phosphate glycerate-3-phosphate 2ADP + 2Pi 2NAD+ 2ATP 2NADH + H+ H 2ADP + 2Pi 2ATP pyruvate 2 triose phosphate 2 glycerate-3-phosphate 2NAD+ H 2NADH + H+ 2ADP + 2Pi 2ATP 2 pyruvate •The triose phosphate is oxidised (loses an electron) •Coenzyme NAD+ collects hydrogen ions forming 2 reduced NAD (NADH +H+ ) •4 ATP are produced, but 2 were used up at the beginning, therefore there is net gain of 2 ATP Overview of Glycolysis Glucose Glycolysis in 2 ATP 2 NADH cytoplasm 2 NADH 2 Pyruvate 4 ATP To mitochondria 2 Pyruvate ATP For use in the cell for work The Link reaction • Literally ‘links’ glycolysis to the Krebs cycle • Sometimes treated as part of the Krebs cycle • Pyruvate enters the matrix of the mitochondria Pyruvate (3C) Link Reaction 2NAD+ H 2NADH + H+ The pyruvate is dehydrogenated (hydrogen is removed) and the hydrogen is transferred to the hydrogen acceptor NAD+ to form NADH + H+ CO2 The pyruvate is decarboxylated (a molecule of carbon is removed) Pyruvate (3C) Link Reaction 2NAD+ H 2NADH + H+ As 2 pyruvate molecules are formed from glucose there will be 2 molecules of acetyl CoA CO2 acetate (2C) + coenzyme A (CoA) acetyl coenzyme A (acetyl CoA) NO ATP is produced The Link reaction pyruvate + CoA + NAD+ Acetyl CoA + CO2 + NADH + H+ Acetyl coenzyme A now enters the Krebs cycle The Link Reaction • Make notes on mitochondria, glycolysis and the link reaction on pages 11 – 13 • Break it down into chunks and make sure you can remember how it starts and what the products are 1. Describe how oxidation takes place in glycolysis 2. What do the terms glycolysis and phosphorylation mean? 3. Why is there only a net gain of 2ATP during glycolysis? 4. How many molecules of ATP are produced in the link reaction? 5. Where is acetyl coenzyme formed? 1. • • • 2. • • 3. • 4. • 5. • Describe how oxidation takes place in glycolysis removal of hydrogen/dehydrogenation; by enzymes/dehydrogenases; H accepted by NAD/reduced NAD formed; What do the terms glycolysis and phosphorylation mean? glycolysis – splitting of glucose Phosphorylation - addition of phosphate Why is there only a net gain of 2ATP during glycolysis? 4 produced but 2 used at beginning so net gain of 2 How many molecules of ATP are produced in the link reaction? none Where is acetyl coenzyme formed? Matrix of the mitochondria