Cellular Respiration and Fermentation Study Outline

Lecture Set 15 & 16 Study Outline - Cellular Respiration and Fermentation 1. Overview of Cellular Respiration Definition : Cellular respiration is a metabolic process in which cells convert biochemical energy from nutrients into ATP, releasing waste products like carbon dioxide and water. Stages : Glycolysis (cytoplasm): Splits glucose into pyruvate. Pyruvate Oxidation (mitochondria): Converts pyruvate to Acetyl-CoA. Citric Acid Cycle (Krebs Cycle) (mitochondrial matrix): Completes the breakdown of glucose in the mitochondrial matrix, generating NADH and FADH?. Oxidative Phosphorylation (Electron Transport Chain & Chemiosmosis) (inner mitochondrial membrane): Produces ATP by transferring electrons and using a proton gradient. Energy Flow : Cellular respiration is a series of redox reactions where glucose is oxidized to carbon dioxide and oxygen is reduced to water, producing ATP in usable units. 2. Key Terms and Concepts Metabolism and Energy Production Catabolic Pathways : Break down molecules to release energy (e.g., cellular respiration). Anabolic Pathways : Use energy to synthesize complex molecules (e.g., photosynthesis). ATP (Adenosine Triphosphate) : The main energy carrier in cells. Respiration vs. Breathing (Ventilation) Breathing (Ventilation) : The physical process of inhaling oxygen and exhaling carbon dioxide. Cellular Respiration : A chemical process where cells use oxygen to produce ATP from glucose. 3. Glycolysis and Fermentation Glycolysis Location : Cytoplasm Process : A 10-step pathway that splits glucose into two molecules of pyruvate, yielding 2 ATP and 2 NADH. ATP is produced by substrate-level phosphorylation. Phases : Energy-Investment Phase : Consumes 2 ATP. Cleavage Phase : Splits the 6-carbon glucose into two 3-carbon molecules. Energy-Yielding Phase : Produces 4 ATP and 2 NADH. Fermentation Anaerobic Process : Occurs in the absence of oxygen to regenerate NAD ? , allowing glycolysis to continue. Types : Lactic Acid Fermentation : Converts pyruvate to lactate, used by muscle cells under low oxygen. Alcoholic Fermentation : Converts pyruvate to ethanol and CO?, used by yeast. NAD ? Regeneration : Essential to keep glycolysis running by allowing the recycling of NADH to NAD ? . Comparison of Glycolysis and Fermentation Glycolysis : Breaks down glucose to pyruvate and produces a small amount of ATP; does not require oxygen. Glycolysis ends with pyruvate. Fermentation : Follows glycolysis if oxygen is absent, generating lactate or ethanol, and regenerates NAD ? . Fermentation starts with pyruvate. 4. Pyruvate Oxidation and the Citric Acid Cycle Pyruvate Oxidation Location : Mitochondria Process : Converts pyruvate to Acetyl-CoA, releasing one molecule of CO? per pyruvate and producing NADH. Citric Acid Cycle (Krebs Cycle) Location : Mitochondrial Matrix Process : Completes glucose breakdown by oxidizing Acetyl-CoA, releasing 2 molecules of CO? per cycle. Products : Per cycle, it yields 3 NADH, 1 FADH?, and 1 ATP (via GTP). ATP is produced by substrate-level phosphorylation . 5. Redox Reactions and Electron Carriers: Oxidation : Loss of electrons. Reduction : Gain of electrons. Redox Processes and Free Energy Release : The transfer of electrons during reduction reactions releases free energy because electrons move from higherenergy states in one molecule to lower-energy states in another, typically towards more electronegative atoms like oxygen . As electrons flow down this energy gradient, the energy released can be harnessed to perform cellular work, such as synthesizing ATP in cellular respiration. Key carriers : NAD ? (NADH) and FAD (FADH?), which transport high-energy electrons to the electron transport chain. 6. Electron Transport Chain (ETC) and Chemiosmosis Electron Transport Chain (ETC) Location : Inner Mitochondrial Membrane Function : Uses NADH and FADH? to transport electrons through a series of protein complexes. Proton Pumps : Upon receiving high-energy electrons from NADH or FADH 2 , proton pumps a ctively transport p rotons (H ? ) from the mitochondrial matrix to the intermembrane space, creating a proton gradient. Oxygen as Final Electron Acceptor : At the end of the ETC, oxygen accepts electrons and protons to form water. Chemiosmosis Proton Gradient : The ETC creates a high concentration of protons in the intermembrane space. ATP Synthase : Protons flow back into the mitochondrial matrix through ATP synthase, generating ATP. 7. Importance of Gradual Free Energy Release Controlled Energy Release : Cellular respiration releases free energy in small steps to prevent damaging the cell. Combustion of Glucose : If glucose burned all at once, it would release energy as heat, which is unusable for the cell and could harm proteins and cellular structures. Efficiency : The stepwise transfer of electrons allows cells to capture energy in small, usable amounts to form ATP. 8. Energy Yield Comparison by Stage Stage ATP Production (Per Glucose) Electron Carriers Byproducts Glycolysis 2 ATP 2 NADH 2 Pyruvate, 2 H?O Pyruvate Oxidation 0 ATP 2 NADH 2 CO? Citric Acid Cycle (Krebs) 2 ATP 6 NADH, 2 FADH? 4 CO? Oxidative Phosphorylation ~28-32 ATP Uses NADH and FADH? from previous steps H?O (from O? as final acceptor) Total theoretical ATP yield per glucose: ~32-36 ATP, depending on cellular conditions. Study Questions Cellular Respiration Overview Describe the purpose of cellular respiration and its main products. Why is it essential to release energy in controlled, small amounts rather than all at once? Glycolysis and Fermentation What is glycolysis, and why is it considered an anaerobic process? How does fermentation allow glycolysis to continue in the absence of oxygen? Compare the two types of fermentation and their respective byproducts. ETC and Proton Pumps Explain the role of the electron transport chain in ATP production. How do proton pumps contribute to the formation of ATP during chemiosmosis? Why is oxygen essential in the ETC? Citric Acid Cycle What are the main outputs of the Citric Acid Cycle, and how do they contribute to ATP production? Respiration vs. Ventilation Differentiate between cellular respiration and ventilation. How does each process contribute to energy production and organismal function? Videos Glycolysis LearnBiology https://youtu.be/uoEaEnbX4I0?si=vKZnf1Gmr8-zeTR8 Cellular Respiration Amoeba Sisters https://youtu.be/eJ9Zjc-jdys?si=J33Kue98-BTMjBIL Rachel Taylor https://youtu.be/X9ipvk39Ff8?si=kLIwy829Rr4acYb5 Science ABC https://youtu.be/JagPP3MX5ks?si=oMZp5whsx3y4F6mW The Citric Acid (Krebs) Cycle Learn Biology https://youtu.be/qgyEt12qHyU?si=6wUT53FuCJRB8go2 Redox Reactions: https://youtu.be/pQLn0zkgRbE?si=UqT68zSjAIZAdw6f https://www.youtube.com/watch?v=qgF5Q6vodeE Electron Transport: Learn Biology https://youtu.be/HkTzr8FuJuQ?si=LmYrCEnTebXS-yHp Professor Dave Explains https://youtu.be/VxCdheLvrx4?si=gTGjI6zvED7MITjv Oxidative Phosphorylation: Professor Dave Explains https://youtu.be/VxCdheLvrx4?si=hNTvarQuN5qqYXOj Fermentation Amoeba Sisters https://youtu.be/YbdkbCU20_M?si=Ql-Yb92fIdJ17m3j Vocabulary List Cellular Respiration: A metabolic process where cells convert nutrients into ATP and release waste products like carbon dioxide and water. ATP (Adenosine Triphosphate): The primary energy carrier used by cells to perform work. Metabolism: The sum of all chemical reactions in an organism, including those that build up (anabolic) and break down (catabolic) molecules. Catabolic Pathways: Metabolic processes that break down molecules and release energy. Anabolic Pathways: Metabolic processes that build complex molecules and require energy input. Glycolysis: A 10-step, anaerobic process in the cytoplasm that breaks down glucose into pyruvate, producing ATP and NADH. Substrate-Level Phosphorylation: A method of ATP production that occurs during glycolysis and the citric acid cycle, where a phosphate group is transferred directly to ADP. Fermentation: An anaerobic process that regenerates NAD? to allow glycolysis to continue when oxygen is absent. Lactic Acid Fermentation: A type of fermentation where pyruvate is converted to lactate, commonly occurring in muscle cells. Alcoholic Fermentation: A type of fermentation where pyruvate is converted to ethanol and carbon dioxide, typically in yeast. Pyruvate: A three-carbon molecule produced from glucose during glycolysis. Acetyl-CoA: A two-carbon molecule derived from pyruvate that enters the citric acid cycle. Citric Acid Cycle (Krebs Cycle): A series of reactions in the mitochondrial matrix that oxidizes AcetylCoA to produce NADH, FADH?, ATP, and CO?. Mitochondrial Matrix: The innermost compartment of the mitochondrion where the citric acid cycle takes place. NAD? / NADH: Nicotinamide adenine dinucleotide; NAD? is an electron carrier that accepts electrons to become NADH. FAD / FADH?: Flavin adenine dinucleotide; another electron carrier involved in cellular respiration. Electron Transport Chain (ETC): A series of proteins in the inner mitochondrial membrane that transfer electrons and help create a proton gradient. Chemiosmosis: The movement of protons across a membrane through ATP synthase to generate ATP. ATP Synthase: An enzyme that synthesizes ATP using the energy from the proton gradient. Proton Gradient: A difference in proton concentration across a membrane, used to drive ATP production. Oxidative Phosphorylation: The stage of cellular respiration involving the ETC and chemiosmosis, producing most of the cell’s ATP. Redox Reaction: A chemical reaction involving the transfer of electrons, including oxidation (loss of electrons) and reduction (gain of electrons). Oxygen (O?): The final electron acceptor in the ETC, which combines with electrons and protons to form water. CO? (Carbon Dioxide): A waste product released during pyruvate oxidation and the citric acid cycle. H?O (Water): A byproduct formed when oxygen accepts electrons at the end of the ETC. Ventilation (Breathing): The physical process of inhaling oxygen and exhaling carbon dioxide. Free Energy: Usable energy released during cellular respiration, used to perform cellular work. Combustion: A rapid chemical reaction that releases energy as heat, unlike the controlled release in cellular respiration. Ethanol: A product of alcoholic fermentation and a molecule metabolized by some organisms for energy.