Chapter 6 Cellular Respiration Part 1 2024 PDF

CHAPTER 6 PART I CELLULAR RESPIRATION: Dr. Samhan HARVESTING CHEMICAL ENERGY  Distinguish between fermentation & cellular respiration Explain catabolic and anabolic pathways in metabolism Describe the structure of ATP Define ox...

CHAPTER 6 PART I CELLULAR RESPIRATION: Dr. Samhan HARVESTING CHEMICAL ENERGY  Distinguish between fermentation & cellular respiration Explain catabolic and anabolic pathways in metabolism Describe the structure of ATP Define oxidation and reduction and explain how redox reactions are involved in energy exchanges. Name the three stages of cellular respiration Describe how the carbon skeleton of glucose changes as it proceeds through glycolysis. Describe where pyruvate is oxidized to acetyl CoA, what molecules are produced OBJECTIVES List the products of citric acid cycle. Describe the point at which glucose is completely oxidized during cellular respiration. Distinguish between substrate-level phosphorylation and oxidative phosphorylation. Summarize the net ATP yield from oxidation of glucose Distinguish between fermentation and anaerobic respiration Compare the fate of pyruvate in alcohol fermentation and lactic acid fermentation Anabolism: Use energy to build complex molecules from simpler ones (e.g., synthesizing proteins from amino acids) Catabolism: Break down molecules to release energy (e.g., cellular respiration breaks down glucose for energy) METABOLISM  Organic molecules (food) store energy in their arrangement of atoms Enzymes catalyze the breakdown of organic molecules rich in energy to simpler products with less energy Some of the released energy is used to form ATP and the rest is dissipated CATABOLISM as heat Metabolic pathways that release the energy from organic molecules are called catabolic  Fermentation: Occurs in the absence of oxygen Produces ATP via glycolysis only, yielding just 2 ATP per one glucose molecule Cellular Respiration: CATABOLISM Requires oxygen Produces ATP through glycolysis, citric acid cycle, and oxidative phosphorylation, yielding up to 32 ATP per one glucose molecule  THE PRINCIPLES OF ENERGY HARVEST 1. Cellular respiration and fermentation are catabolic, energy-yielding pathways 2. Cells use the ATP for work 3. Redox reactions release energy when electrons move between atoms 4. In cellular respiration, electrons “fall” from organic molecules to oxygen 5. The “fall” of electrons during respiration is stepwise and needs a carrier  Cellular respiration: Is a catabolic pathway that releases energy by breaking down complex molecules Food is the fuel for cellular respiration CELLULAR RESPIRATION Cellular respiration involves movement of electrons (gain or loss) Organic compounds + O2 → CO2 + H2O + energy We will study the breakdown of glucose as an example  ATP (Adenosine Triphosphate): Consists of adenine, ribose (a sugar), and three phosphate groups ATP stores energy in the high- energy bonds between its phosphate groups STRUCTURE OF Function: ATP ATP transfers energy for cellular work by releasing one phosphate group to form ADP (adenosine diphosphate) ADENOSINE TRI-PHOSPHATE (ATP) + H2O Energy +  PHOSPHORYLATION Transfer of the terminal phosphate group from ATP to another molecule changes the shape of the receiving molecule to become active Then when the phosphate groups leaves the molecule, the molecule returns to its original shape (inactive)  In cellular respiration, glucose and other fuel molecules are oxidized, releasing energy Glucose is oxidized, oxygen is reduced, and electrons loose potential energy H+ is the source of electrons transferred to O- Glucose has abundance of hydrogen which CELLULAR are source of electrons that “fall” to oxygen RESPIRATION Enzymes (dehydrogenases) are needed to ELECTRONS lower the activation energy, allowing these “FALL” FROM fuels to be oxidized ORGANIC The resulting energy is used by the cell to MOLECULES TO OXYGEN synthesis ATP e- C6H12O6 + 6O2 6CO2 + 6H2O + (ATP + Heat) Reducing Oxidizing Energy = 686 kcal/mol agent agent Energy  Oxidation: Loss of electrons from a molecule Reduction: Gain of electrons by a molecule OXIDATION Redox Reactions: AND In cellular respiration, glucose is REDUCTION oxidized, and oxygen is reduced These reactions are essential for IN energy production in cells METABOLISM  Cellular respiration does not oxidize glucose in a single step Glucose and other fuels are broken down gradually in a series of steps, REDOX each catalyzed by a specific dehydrogenase enzyme REACTIONS IN Redox reactions transfer electrons ENERGY between molecules, which drives the EXCHANGE production of ATP Electron Carriers (coenzymes): Molecules like NADH and FADH play key roles in transferring electrons during cellular respiration.  NADH carries electrons to the ROLE OF electron transport chain (ETC) NADH IN Oxidation: NADH is oxidized CELLULAR back to NAD+ in the ETC, which allows ATP production through RESPIRATION oxidative phosphorylation  Like NADH, FADH2 carries electrons to the ETC but feeds ROLE OF FADH2 electrons at a later point than IN CELLULAR NADH RESPIRATION FADH2 contributes to the production of fewer ATP molecules compared to NADH  The electron transport chain, consisting of several molecules (primarily proteins), is built into the inner membrane of a mitochondrion NADH takes electrons from food to the “top” of the chain At the “bottom”, oxygen captures the electrons and H+ to form water  Final Electron Acceptor: Oxygen is the final electron acceptor in the ETC. Without ROLE OF oxygen, the ETC cannot function OXYGEN IN Oxygen combines with electrons CELLULAR and protons to form water, a byproduct of cellular respiration RESPIRATION Without oxygen, oxidative phosphorylation halts, forcing cells to rely on fermentation or anaerobic respiration SUMMARY OF ELECTRON “FALL” STEPS DURING RESPIRATION - Falling of all H atoms from glucose to O is gradually not at once - It occurs in steps, each one is catalyzed by an enzyme - - H atoms of glucose pass first to the co-enzyme NAD+ to form NADH - - Then from NADH to electron transport chain, and finally to O and releases energy to form ATP Mitochondrion NAD+ e e Food H NADH Transport chain Oxygen Energy ATP ADP