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Summary of Metabolism End of Ch9 and Start of CH10 October 9

Understand glycolysis, cellular energy storage, key pathways, and coenzymes for energy transfer in cellular metabolism. Learn about ATP, redox reactions, and the role of mitochondria in generating ATP. Key points for test preparation provided.

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Summary of Metabolism End of Ch9 and Start of CH10 October 9

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  1. Summary of Metabolism End of Ch9 and Start of CH10 October 9 Chapter 6,7, 8 and 9 for Friday’s Lecture test Background to understanding glycolysis What is glycolysis? Cellular specialization and localization Classic molecules of metabolism Requirements for molecules in a cell Requirements to additive Delta G

  2. Overview of Cellular Metabolism (CH9-10) Most cellular energy originates from photosynthesis and carbon fixation Three ways to think about “energy” in a cell: • Energy: storage as triglycerides or glycogen • Energy: transported as glucose or fatty acid • Energy: transfer between reactions as ATP or NADH Key Pathways for releasing energy: • Glycolysis occurs in cytosol and permits partial oxidation of glucose to pyruvate ATP and NADH in presence of oxygen (best) or absence (2nd best). • Fatty acid oxidation by beta oxidation occurs only in mitochondria but only in presence of oxygenacetate • FA and Glycolytic products oxidized to ATP, NADH, FADH2 and CO2 by Citric Acid Cycle in mitochondria (O2 dependent) Mitochondria is key to eukaryotic metabolism: • Oxidative phosphorylationoccurs in mitochondria when NADH and FADH2 are present and requires oxygen as final electron acceptor tremendous ATP yield and water! Idea: generate a proton gradient across inner mitochondrial membrane and use gradient energy to phosphorylate ADP + Pi  ATP.

  3. Localization of metabolism to specific eukaryotic organelles/locations. Remember that Delta G for several chemical reactions is ONLY ADDITIVE if the reactions are not seperated by a phospholipid bilayer! THIS IS SUPER IMPORTANT! Catabolic Pathways • Glycolysis (glucosepyruvate): cytosol • Citric Acid Cycle (PyruvateacetateCO2): mitochondria • Beta-oxidation (fatty acids acetate): mitochondria • Oxidative Phosphorylation (NADH/FADH2 oxygen) mitochondria Anabolic Pathways • Photosynthesis: chloroplast • Gluconeogenesis: cytosol Main Locations of additive Delta G in Eukaryotic Cells: cytosol, mitochondria, chloroplast

  4. Why is adenosine triphosphate (ATP) such a great energy carrier? • ATP: adenosine + Ribose + 3XPO4 • ATP + H2O ADP + Pi • Delta G for Pi hydrolysis: -7.3 kcal/mol • Delta G for ATP synthesis: + 7.3 kcal/mol ATP IS WATER SOLUBLE AND CHEMICALLY STABLE! • Bonds to/from/between phosphate groups: • Phosphoanhydride bonds(X2): X-O-X next to a double bonded oxygen • Phosphoester bond (X1): X-O-X next to no double bonded oxygen • Charge repulsion between (-) charged Pi groups is massive! • Covalent bonds hold groups together against repulsion,,,barely! • Each Pi has an extra electron (-) that resonates between the oxygen atoms and stabilizes the structure!

  5. On a test could you name the bond types, identify the parts, and describe the delta G?

  6. Resonance means that the electron actually splits its time between being located on different atoms in PO4. The electron is moving around the P-center, creating partial negative charges all around it.

  7. Lets review the major types of reaction that occur in cells, especially with regards to energy and enzymes. • 1) Catabolic vs. Anabolic • 2) “XXX-ase” refers to an enzyme that causes a specific reaction • 3) Group transfer reaction: functional group moves location: “Transferase” • 4) Oxidation: electron removed from target • Dehydrogenase: enzyme removes an electron and the proton (hydrogen ion) that goes with it! • 5) Reduction: electron added to target, often with a proton. • Hydrogenase

  8. How do coenzymes help enzyme reactions in a cell? Coenzymes are molecules that carry or stabilize the electrons or functional groups for an enzyme. NAD+ (Nicotinamide Adenine Dinucleotide) is the CLASSIC! Classic coenzyme:Niacin connection to vitamins in diet Contents:Charged nicotinamide+Ribose+Diphosphate Bridge+Ribose+Adenine base Oxidized: NAD+ low energy Reduced: NADH HIGH ENERGY Electron and proton represent potential energy!

  9. The Trick: the nicotinamide functional group either has a charge (NAD+; oxidized;low energy) or has an extra electron and proton (reduced; high energy; NADH). The Nic-ring structure stabilizes the extra electron so the energy in the electon can be transferred between molecules. NADH electrons mostly used in the mitochondria (not cytosol).

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