Energy and Respiration Why living organism need energy? From where it come? How we take this energy? The need for energy in living organisms continuous supply of energy for: Synthesis of complex substances from simpler ones (anabolic reactions) Active transport (movement of molecule) Mechanical work – movement Maintenance of internal body temperature What is ATP Adenosine triphosphate Energy released is not then directly used, it is passed on to ATP. ATP is made of: Adenine Ribose 3 phosphate molecules ATP is energy currency When a phosphate group is removed from ATP, ADP is formed and energy is released. ATP + H2O = ADP + H3PO4 ± 30.5kJ AMP ± 14.2kJ ATP is the universal intermediary molecule. It is known as the energy currency. ATP is energy currency Energy currency & storing Energy currency- act as a immediate donor of energy to the cell energy requiring reaction. Energy storage- a short term (glucose/sucrose) long tem (glycogen, starch, triglycerides) Synthesis of ATP 1. Energy released by reorganizing chemical bonds (glycolysis and Krebs cycle) . 2. Using electrical potential energy when electrons are transferred by electron carriers. This is called chemiosmosis. Hydrogen carrier molecules (NAD & FAD) . Respiration Organic molecules are broken down to release energy to make ATP. Two types: A) Aerobic respiration – in the presence of oxygen. B) Anaerobic respiration – in the absence of oxygen. Both start with glycolysis. Respiration 4 main stages... 1. Glycolysis 2. The Link Reaction 3. The Krebs Cycle 4. The Electron Transport Chain Respiration Glycolysis Phosphorylation (adding phosphate) to glucose using ATP Occurs in the cytoplasm. Splitting hexose phosphate (6C) into two triose phosphate molecules (3C) These are then oxidised, releasing ATP and reducing NAD Glucose (hexose) (6C) Hexose phosphate (6C) produced by phosphorylation using ATP Hexose bisphosphate (6C) adding another phosphate using ATP This splits into two 2 molecules of triose phosphate (3C) A sequence of Intermediate molecules are formed, by reducing NAD and losing phosphates to produce 4 molecules of ATP 2 x Pyruvate (3C) Glucose 1st Phosphorylation Glucose-6Phosphate Isomerisation 1. Glycolysis H+ taken to reduce NAD 2 x ATP PYRUVI C ACID Triose Phosphate Fructose-6Phosphate H+ taken to reduce NAD 2 x ATP PYRUVI C ACID Triose Phosphate Fructose-1-6 Bisphosphate They are then converted into pyruvic acid.splits This involves removal ofcalled hydrogen and it’s transfer to a This The isThe fructose-1-6-bisphosphate then phosphorylated forobtained a then second time, into splitting twothe molecules aproduct molecule ofvia ATP, TRIOSE forming PHOSPHATE. fructose-1The glucose The glucose glucose-6-phosphate is phosphorylated molecule is into changes glucose-6-phosphate as the to fructose-6-phosphate digested by taking of eating a phosphate isomerisation carbohydrates from ATP hydrogen carrier molecule (NAD) to form reduced NAD. Each pyruvic acid yields 2 molecules of ATP in the They each have 6-bisphosphate 3 carbons and 1 phosphate process of it’s creation Glycolysis- Summary • • • • • • Breaking down a glucose molecule into two molecules of pyruvate (pyruvic acid) It uses 2 ATP molecules for substrate level phosphorylation It creates 4 ATP molecules There is a NET TOTAL of 2 ATP molecules made. The 2 reduced NAD made goes to the electron transport chain The 2 molecules of pyruvate go into the link reaction Glycolysis- Summary Process Glycolysis Number of ATP used (per glucose) 2 Number of ATP produced (pg) 4 Net Total ATP (pg) 2 Number of reduced NAD produced (pg) 2 Number of reduced FAD produced (pg) 0 Other products made (pg) 2 molecules of pyruvic acid The Link Reaction The Krebs Cycle Link reaction Occurs when oxygen available It is decarboxylated (carbon removed) Dehydrogenated (hydrogen removed) As a result of this, CO2 is formed and NAD is reduced 2. The Link Reaction From Glycolysis To Krebs Cycle PYRUVIC ACID (3C) ACETATE Acetyl coA 2C H+ to reduce NAD The link reaction connects Glycolysis tocycle the cyclethe Krebs via This forms which is taken by coenzyme Amitochondrial (coA) recycled from cycle to This isacetate, decarboxylated The pyruvic via acid decarboxylase diffuses into tothe the produce CO and dehydrogenated matrix This isup taken into krebs 2 Krebs coA dehydrogenase to produceform H+ , acetyl used to reduced a molecule of NAD The Link Reaction- Summary Process Glycolysis The Link Reaction Number of ATP used (per glucose) 2 0 Number of ATP produced (pg) 4 0 Net Total ATP (pg) 2 0 Number of reduced NAD produced (pg) 2 2 Number of reduced FAD produced (pg) 0 0 Other products made (pg) 2 molecules of pyruvic acid 2 x Carbon Dioxide 2 x Acetyl coA The Krebs Cycle Krebs cycle Closed pathway of enzyme-controlled reactions Occurs in matrix of mitochondria Acetyl CoA (2C) enters the cycle and joins with a 4 carbon compound to make a 6 carbon compound. A series of steps now transfer the 6C (citrate) back to the 4C (oxaloacetate) These steps include more decarboxylation and dehydrogenation Pg 203 LINK REACTION. Pyruvate molecules (3-carbon) from glycolysis are converted into another type of molecule called Acetyl-CoA in a process known as pyruvic oxidation. This conversion occurs when the pyruvate is broken down by a complex of 3 enzymes called pyruvate dehydrogenase, releasing a carbon atom which goes on to form carbon dioxide (CO2). The 2 remaining carbon molecules bond with coenzyme A forming Acetyl-CoA. During this process, electrons and a hydrogen ion are passed to NAD+, thus oxidizing the pyruvate, hence the name of the process. Step 1. The Acetyl-CoA then enters the Krebs cycle. It initially combines with a 4-carbon molecule called oxoaloacetic acid, forming a 6-carbon molecule of citric acid (citrate). This reaction is catalyzed by the enzyme citrate synthase. Upon this formation, the coenzyme A is released, returning to the link reaction. Step 2. The citrate molecule is then dehydrated (H20 molecule is removed) and then rehydrated by the enzyme aconitase. The resulting molecule is just a rearranged form of citrate known as isocitrate. Step 3. Next, isocitrate undergoes what is known as a oxidative carboxylation, which simply means that a carbon and hydrogen are given off. The result of this is a 5-carbon molecule called alpha-ketoglutarate. This process is catalyzed by the enzyme isocitrate dehydrogenase. Additionally, the carbon that broke off forms CO2, while the hydrogen reduces NAD+ to form NADH. Step 4. In the next reaction, alphaketoglutarate has yet another carbon molecule removed and is then transferred to a CoA molecule by the enzyme alpha-ketoglutarate dehydrogenase. The resulting product is a 4-carbon molecule of Succinyl-CoA. Additionally, CO2 and NADH is formed. Step 5. After succinyl-CoA is formed, the molecule then undergoes the removal of the CoA carrier, resulting in the production of succinate. Additionally, the enzyme succinylCoA synthetase that removes the CoA also produces GTP (Guanosine Triphosphate) through substrate level phosphorylation (phosphate molecule directly added to another molecule). (GTP is a high energy molecule similar to ATP, and later an ADP molecule takes the phosphate from GTP and makes ATP) Step 6. Next, succinate is dehydrated by the enzyme succinate dehydrogenase. The resulting product is furmate. Step 7. Furmate is then hydrated (water added) by enzyme furmase to form malate Step 8. Lastly, the malate is dehydrogenated by the enzyme malate dehydrogenase, forming the original molecule oxaloacetate. From this reaction, NADH and H+ are also produced. SUMMARY Every pyruvate molecule that enters the Krebs cycle generates 3 molecules of CO2, one molecule of ATP, one molecule of FADH and 4 molecules of NADH ADP+P ATP Pyruvate 3CO2 4NAD+ 4NADH FAD+ FADH The reduced NAD and FAD molecules enter the electron transfer chain, and result in a large number of ATP molecules being produced. Acetyl coA 2C Oxaloacetic Acid 4C 3. The Krebs Cycle Citric Acid 6C Keto-Glutaric Acid 5C 1x ATP Malic Acid 4C Succinic Acid 4C The function of the Krebs cycle is a means of liberating from carbon bonds toreduce The This Acetyl 6C 4C Compound coA compound enters (citric the isisthen Krebs acid) dehydrogenated Cycle undergoes combining decarboxylation again. This aenergy 4C H+ and acid ion dehydrogenation emitted to again, form is aproducing 6C used compound. produce This 5C compound then decarboxylated and with dehydrogenated aprovide 4C The Oxaloacetic acid is by regenerated from malic acid by atofinal ATP, r.NAD and r.FAD , with the release of carbon dioxide CO and H+ ion, Thethis Acetyl is used is regenerated to reduce an andNAD. recycle These back processes into link produced reaction Compound. This produced enough energy to synthesise the the production of a1 5C ATPcompound Molecule 2 FAD reducing NAD dehydrogenation, The Krebs Cycle- summary Per cycle we obtain… 1 ATP 3 r.NAD 1 r.FAD 2 Carbon Dioxide Molecules Remember that the Krebs Cycle turns twice per glucose molecule. The Krebs Cycle -Summary Process Glycolysis The Link Reaction The Krebs Cycle Number of ATP used (per glucose) 2 0 0 Number of ATP produced (pg) 4 0 2 Net Total ATP (pg) 2 0 2 Number of reduced NAD produced (pg) 2 2 6 Number of reduced FAD produced (pg) 0 0 2 Other products made (pg) 2 molecules of pyruvic acid 2 x Carbon Dioxide 4 x Carbon Dioxide 4. The Electron Transport Chain • A series of carriers and pumps, releasing energy in the form of ATP Electron Transport Chain 1. 2. 3. NADH and FADH2 oxidised - electron and proton released electron picked up by an electron carrier on the inner membrane It is passed from one acceptor to another along a chain. electron has a high potential energy at beginning of chain but as it is passed along the electron falls to a lower energy state. energy released actively pumps the hydrogen ion (proton) into the intermembrane space. electron reaches the end of the chain it rejoins to the hydrogen ion to make a hydrogen atom. These hydrogen atoms then join to oxygen to form water. 4. The Electron Transport Chain 4. The Electron Transport Chain Inter membrane space High Concentration of H+ ions - The pump is pumping them from the matrix, they are taking them from reduced NAD and FAD ATP PUMP PUMP PUMP Low Concentration of H+ ions is maintained -When they pass through ATP synthetase they combing with oxygen and electrons to form water. Matrix ATP SYNTHETASE Chemiosmosis hydrogen ions actively transported into the intermembrane space. Chemiosmosis is the movement of ions across a selectively-permeable membrane, down their electrochemical gradient. Energy Budget Process Glycolysis The Link Reaction The Krebs Cycle Number of ATP used (per glucose) 2 0 0 Number of ATP produced (pg) 4 0 2 Net Total ATP (pg) 2 0 2 Number of reduced NAD produced (pg) 2 2 6 Number of reduced FAD produced (pg) 0 0 2 Other products made (pg) 2 molecules of pyruvic acid 2 x Carbon Dioxide 4 x Carbon Dioxide Energy Budget Altogether, per molecule of glucose, we obtain Each reduce FAD is capable of making 2 ATP 4 ATP in the electron transport chain 10 r.NAD x 3 = 30 ATP 2 r.FAD x 2 = 4 ATP • Altogether, per glucose molecule, 38 ATP are made Each reduce NAD is capable of making 3 ATP in the electron transport chain Anaerobic Respiration In the absence of oxygen only glycolysis can take place The rNAD/rFAD cannot be reoxidised and therefore able to pick up more hydrogen so the link reaction and krebs can’t occur The yield of ATP is only 2 - If there is no oxygen there is no where for the hydrogen to go - which then blocks the electron transport chain - which stops the NAD from being regenerated - so the krebs cycle is blocked - so the link reaction is blocked - and only glycolysis can occur – anaerobic respiration. Anaerobic Respiration To regenerate NAD to be able to continue glycolysis, pyruvate becomes the hydrogen acceptor. This either forms lactic acid or ethanol. In animals end product is lactic acid C6H12O6 → 2CH3CH(OH)COOH + 2 ATP In plants and yeast end product is ethanol and carbon dioxide C6H12O6 → 2CH3CH2OH + CO2 + 2ATP Lactic acid is produced just by adding 2 hydrogen molecules to pyruvate. Ethanol is produced by first removing a carbon molecule (releasing carbon dioxide) and then adding the 2 hydrogen molecules. That is why alcoholic fermentation is accompanied by evolution of carbon dioxide. Anaerobic Respiration Fermentation Takes place in yeast where the pyruvate is converted into alcohol and carbon dioxide 1. The pyruvate is first decarboxylated to produce ethanal 2. The hydrogen released during glycolysis is passed to NAD 3. Reduced NAD passes its hydrogen to ethanal, reducing it to ethanol • Plants cannot use the ethanol. It cannot be converted back into pyruvate and it cannot be oxidised The ethanol is toxic and if anaerobic respiration continues for too long the plant will be poisoned and die. Seeds and plants growing in waterlogged conditions can respire anaerobically for a short time. Adaptation of rice to anaerobic condition 1. Plant grow taller so leaves have access to oxygen in atmosphere. 2. Stem and root have loosely packed cell, parenchyma, with large air space. That allow diffusion of oxygen from air part. 3. contain high level of enzyme alcohol dehydrogenase, when oxygen available it convert ethanol back to ethanal. 4.Rice tissue are tolerant to ethanol. Anaerobic Respiration • • • During vigorous exercise the human body has to respire anaerobically This involves glycolysis , but the reduced NAD produced passes it’s protons straight to pyruvic acid, reducing it to lactic acid A build up of lactate can cause muscle cramp. When oxygen becomes available it is broken down by the liver. Most is converted to glycogen and stored. Anaerobic Respiration Respiratory Quotient It is a unitless number used in calculations of basal metabolic rate (BMR) It is the ratio of the volume of carbon dioxide released to the volume of oxygen consumed by a body tissue or an organism in a given period. The respiratory quotient (RQ) is calculated from the ratio: RQ = CO2 eliminated / O2 consumed The range of respiratory coefficients for organisms in metabolic balance usually ranges from 1.0 (representing the value expected for pure carbohydrate oxidation) to ~0.7 (the value expected for pure fat oxidation). Carbohydrates The value of RQ is equal to 1 if carbohydrates are the respiratory substrates in aerobic respiration. Fats When the respiratory substrate is fat, the RQ is about 0.7. Example: Tripalmitin Fats contain less oxygen than carbohydrates and so they require more oxygen for oxidation. Anaerobic respiration The value of RQ is infinity during anaerobic respiration because CO2 is produced but O2 is not utilised. Measuring RQ This is done by measuring the change in the volume of gas surrounding the material as it respires – first as carbon dioxide is absorbed (to measure the rate of oxygen consumption) and then without absorbing the carbon dioxide (from which you can calculate the rate of production of carbon dioxide by comparison with the first measurment). The apparatus consists of two vessels. One vessel contains the organisms and the other acts as a thermobarometer – small changes in temperature or pressure cause air in this vessel to expand or contract, compensating for similar changes in the first vessel. Changes in the manometer level are thus due only to the activities of the respiring material.