Cellular Respiration PDF

CELLULAR RESPIRATION Mohd Aminudin Bin Mustapha  Objectives Describe two types of cellular respiration: Aerobic cellular respiration and anaerobic cellular respiration Briefly describe processes glycolysis, link reaction,...

CELLULAR RESPIRATION Mohd Aminudin Bin Mustapha  Objectives Describe two types of cellular respiration: Aerobic cellular respiration and anaerobic cellular respiration Briefly describe processes glycolysis, link reaction, Krebs Cycle, electron transport chain and chemiosmosis Define facultative anaerobes and obligate anaerobes Briefly describe alcoholic fermentation and Lactate fermentation Briefly describe other sources of energy. Cellular Respiration 2  Cellular Respiration Definition: A series of biochemical reactions in cells that involve the breakdown and oxidation of organic molecules, primarily sugars, to release energy. Energy Utilization: Part of the energy is released as heat. The rest is stored as chemical energy in the form of adenosine triphosphate (ATP). Purpose: Living organisms require energy for movement, maintaining constant body temperature, anabolic processes, and active transport. Cellular Respiration 3  Types of Cellular Respiration Aerobic Cellular Respiration: Food is completely oxidized with the help of oxygen into carbon dioxide and water. Anaerobic Cellular Respiration: Food is oxidized without using oxygen, e.g., in yeast and bacteria. Cellular Respiration 4  Processes Involved in Cellular Respiration Oxidation: Removal of hydrogen (involves loss of electrons); the liberated hydrogen is transferred to another compound. Reduction: Addition of hydrogen (involves gain of electrons). Phosphorylation: Addition of a phosphate group to another compound. Presentation title 5  Processes Involved in Cellular Respiration Substrate-level Phosphorylation: Transfer of a phosphate group from a phosphorylated substrate to ADP, forming ATP. Isomerization: Conversion of a compound to its isomer molecule; isomers have the same formula but different atom arrangements. Main Objective: Produce ATP for energy. Cellular Respiration 6  Aerobic Cellular Respiration Definition: Biochemical redox reactions in living cells in the presence of oxygen. Redox Reaction: Transfer of electrons from a reducing agent to an oxidizing agent, releasing energy. Example: Oxidation of glucose (C₆H₁₂O₆) to CO₂ and reduction of oxygen to water. Cellular Respiration 7  Stages in Aerobic Cellular Respiration 1. Glycolysis: Occurs in the cell cytoplasm. 2. Link Reaction: Occurs in the mitochondrial matrix. 3. Krebs Cycle: Occurs in the mitochondrial matrix. 4. Electron Transport Chain: Occurs in the inner mitochondrial membrane. Cellular Respiration 8  Glycolysis 1. Phosphorylation of 6C glucose. 2. Isomerization: Glucose-6- phosphate to fructose-6- phosphate. 3. Phosphorylation: Fructose- 6-phosphate to fructose- 1,6-diphosphate. Cellular Respiration 9  Glycolysis 4. Cleavage: Fructose-1,6- diphosphate split into two 3C molecules (G3P and dihydroxyacetone phosphate). Cellular Respiration 10  Glycolysis 5. Oxidation, phosphorylation, and substrate-level phosphorylation: G3P to 3-phosphoglycerate (3PG), forming NADH and ATP. 6. 1,3-bisphosphoglycerate is hydrolyzed to form 3- phosphoglycerate (3PG), resulting in the production of ATP. Cellular Respiration 11  Glycolysis 7. Isomerization: 3PG to 2- phosphoglycerate (2PG). 8. Dehydration: 2PG to phosphoenolpyruvate (PEP). 9. Substrate-level phosphorylation: PEP to pyruvate, forming ATP. Cellular Respiration 12  Net Products Glycolysis 2 ATP (net gain) 2 NADH (transported to the electron transport chain) 2 pyruvate (transported to the link reaction) Cellular Respiration 13  Link Reaction Occurs with oxygen. Carbon dioxide is removed. Hydrogen atoms are transferred to NAD+ to form NADH. Pyruvate is converted to acetyl-CoA. Cellular Respiration 14  Krebs Cycle Coenzyme A assists the acetyl (2C) molecule in entering the Krebs Cycle and then detaches to be reused. This process occurs only in the presence of oxygen. Its significant role includes the formation of NADH and FADH2, which carry high-energy electrons and H + ions to the Electron Transport Chain. Cellular Respiration 15  Krebs Cycle 1. Condensation: Acetyl (2C) to oxaloacetate (4C), forming citrate (6C). 2. Isomerization: Citrate to isocitrate (6C). 3. Oxidative Decarboxylation: Isocitrate to α-ketoglutarate (5C), releasing CO₂ and forming NADH. Cellular Respiration 16  Krebs Cycle 4. Oxidative Decarboxylation: α- ketoglutarate to succinyl- CoA (4C), releasing CO₂ and forming NADH. 5.Substrate-level Phosphorylation: Succinyl- CoA to succinate (4C), forming GTP (converted to ATP). Cellular Respiration 17  Krebs Cycle 6.Oxidation: Succinate to fumarate (4C), forming FADH₂. 7.Hydration: Fumarate to malate (4C). 8.Oxidation: Malate to oxaloacetate (4C), forming NADH. Cellular Respiration 18  Overall Products Krebs Cycle 6 NADH 2 FADH₂ 2 ATP 4 CO₂ (per glucose molecule, as the cycle runs twice per glucose) Cellular Respiration 19  Summary of Glycolysis to Krebs Cycle This outline provides a structured overview of the key components and stages involved in cellular respiration, emphasizing the biochemical processes and their significance in energy production. Cellular Respiration 20  Electron Transport Chain Involves oxidation and reduction processes Transfers electrons from NADH and FADH2 Plays a significant role in ATP production Cellular Respiration 22  Electron Transport Chain Contains three proton pumps (Complexes I, III, and IV) connected by two mobile electron carriers (Coenzyme Q and Cytochrome C) Complex Complex I NADH reductase Complex II Succinate dehydrogenase Complex III Cytochrome reductase Complex IV Cytochrome oxidase Cellular Respiration 23  Electron Transport Chain NADH and FADH2 , in their reduced forms, carry high-energy electrons and hydrogen ions (H + ) These carrier molecules transport the high-energy electrons and H + ions from glycolysis, the link reaction, and the Krebs cycle to the electron transport chain in the inner mitochondrial membrane Cellular Respiration 24  Electron Transport Chain There are two entry points into the ETC: Complex I for NADH and Complex II for FADH2 Cellular Respiration 25  Electron Transport Chain Electron flow from NADH: Complex I → CoQ → Complex III → Cyt. c → Complex IV Electron flow from FADH2 : Complex II → CoQ → Complex III → Cyt. c → Complex IV Cellular Respiration 26  Electron Transport Chain Complex II does not transport protons across the membrane and only contributes to the proton gradient minimally, similar to CoQ and Cyt. c Cellular Respiration 27  NADH in the Electron Transport Chain NADH binds to Complex I and releases its 2 hydrogen atoms (H + and electrons) into the ETC NAD + returns to the Krebs cycle Electrons pass from one carrier molecule to the next, moving down the energy gradient from the high-energy NADH to the final electron acceptor, oxygen, where water (H2 O) is formed Cellular Respiration 28  FADH2 in the Electron Transport Chain FADH2 at Complex II releases its H+ and electrons to Coenzyme Q Each successive acceptor molecule is reduced when it receives electrons and then oxidized when it passes them on The final transfer involves combining electrons and H2 atoms with oxygen to form water at Complex IV Oxygen is the final electron acceptor and has the highest electronegativity Cellular Respiration 29  Creation of Hydrogen Ion Gradient As electrons are passed down the chain, some of their energy is used to pump H+ ions out of the mitochondrial matrix into the intermembrane space Proton pumping occurs only at Complexes I, III, and IV This creates a transmembrane electrochemical proton gradient. Cellular Respiration 30  Creation of Hydrogen Ion Gradient H+ ions, highly concentrated in the intermembrane space, flow back across the membrane down the electrochemical gradient through ATP synthase The inner mitochondrial membrane is impermeable to H+ ions, so they diffuse through ATP synthase only Cellular Respiration 31  Phosphorylation of ADP Chemiosmosis refers to the diffusion (osmosis) of ions across a selectively permeable membrane down the electrochemical gradient As H + ions move back across the membrane and release energy, ATP synthase phosphorylates ADP to ATP Cellular Respiration 32  Phosphorylation of ADP This process is called oxidative phosphorylation because it requires oxygen Inhibitors can bind to components of the electron transport chain, blocking electron transfer and stopping proton pumping and ATP synthesis Cellular Respiration 33  Total ATP Produced: 36 or 38? ATP formation during glycolysis involves shuttle systems 2 NADH molecules from glycolysis in the cytoplasm are not directly accessible to the ETC due to the mitochondrial inner membrane being impermeable to NADH Cellular Respiration 34  Total ATP Produced: 36 or 38? Two shuttle systems transport energy from NADH across the membrane: o Malate-aspartate shuttle (NADH) o Glycerol-3-phosphate shuttle (FADH) Oxidation of one NADH molecule synthesizes three ATP molecules, while oxidation of FADH2 yields two ATP molecules Cellular Respiration 35  Malate-Aspartate Shuttle Occurs in the liver, kidneys, and heart during glycolysis Electrons are carried in the form of malate NADH is regenerated inside the mitochondrial matrix Total ATP produced is 38 Cellular Respiration 36  Glycerol-3-Phosphate Shuttle Occurs in skeletal muscles and the brain during glycolysis Electrons are transferred from NADH to FAD in the mitochondria FAD is reduced to FADH2 Newly formed FADH2 passes electrons to CoQ of the ETC, generating 2 ATP per electron pair Total ATP produced is 36 Cellular Respiration 37  Aerobic Cellular Respiration (Lipid) Fats can serve as a source of energy Fats are broken down into fatty acids and glycerol Glycerol converts to glyceraldehyde 3-phosphate, which undergoes glycolysis, the link reaction, the Krebs cycle, and the ETC Cellular Respiration 38  Aerobic Cellular Respiration (Lipid) Fatty acids undergo β- oxidation, splitting into 2- carbon fragments and converting to acetyl groups that combine with coenzyme A to form acetyl CoA, which enters the Krebs cycle Each β-oxidation process requires one ATP to prime but produces one NADH and one FADH2 Cellular Respiration 39  Anaerobic Respiration (Fermentation) Allows glycolysis to occur with a small amount of ATP production and regeneration of NAD + Facultative anaerobes can respire aerobically or carry out anaerobic respiration when oxygen is limiting (lactic acid fermentation) Obligate anaerobes only respire anaerobically and live in low- or no-oxygen environments (alcoholic fermentation) Cellular Respiration 40  Alcoholic Fermentation Occurs in some fungi, yeast, bacteria, and earthworms Pyruvate (3C) converts to CO2 and ethanol (EtOH) Yeast enzymes remove CO2 from pyruvate, yielding acetaldehyde (2C) - decarboxylation Acetaldehyde accepts electrons from NADH, converting to EtOH and regenerating NAD+ needed for glycolysis Pyruvate and NADH are products of glycolysis Cellular Respiration 41  Lactic Acid Fermentation Occurs in vertebrate skeletal muscles that contract actively Pyruvate is reduced by NADH to form lactate without releasing CO2 , regenerating NAD+ Lactate accumulation causes fatigue, cramping, and lower blood pH Oxygen debt is repaid by deep, rapid breathing to break down lactate After strenuous activity, lactate is oxidized back to pyruvate in the liver Cellular Respiration 42  Importance of Anaerobic Respiration Regenerates NAD+ for glycolysis Cellular Respiration 43