bio

• Cellular respiration is the complete oxidation of glucose
• NAD+ accepts 2 electrons and 1 proton to become NADH
• Energy metabolism


  • Concerned with redox reactions and dehydrogenations
• Cellular respiration


  Series of reactions where cells utilize enzyme-facilitated redox reactions to convert energy from food sources to ATP
• Redox reactions

  Electrons carry energy from one molecule to another
• Final electron acceptor in anaerobic respiration

  Is an inorganic molecule (not O2)
• Nicotinamide adenosine dinucleotide (NAD+) is an electron carrier and enzymatic cofactor used in oxidation-reduction reactions
• High-energy electrons from initial chemical bonds are transferred to a final electron acceptor
• During redox reactions, electrons carry energy from one molecule to another
• Types of organic compounds in foods

  • Carbohydrates, proteins, fats
• Organisms can be classified based on how they obtain energy: Autotrophs (self-feeders) and Heterotrophs
• All organisms use cellular respiration to extract energy from organic molecules
• Final electron acceptor in fermentation

  Is an organic molecule
• Final electron receptor in aerobic respiration

  Is oxygen (O2)
• Cellular respiration

  The oxidation of organic compounds to extract energy from chemical bonds
• Free energy can be even higher than -686 kcal/mol in a cell
• Fermentation


  Final electron acceptor is an organic molecule
• Electron transport

  ATP is generated when electrons transfer from one energy level to another. Electrons "fall" to lower and lower energy levels in steps, releasing stored energy with each fall as they tumble to the lowest (most electronegative) electron acceptor, O2
• Cells make ATP by two fundamentally different mechanisms
• In animals, when ATP is plentiful, the reducing power of accumulated NADH is diverted to supplying fatty acid precursors with high-energy electrons, reducing them to form fats used for long-term energy storage
• ∆G (free energy) of hydrolyzing terminal phosphate = -7.3 kcal/mol
• This large amount of energy in aerobic respiration must be released in small steps rather than all at once
• Electron carriers

  • Soluble carrier (NAD+), membrane-bound carrier, carrier that moves within membrane
• Aerobic respiration


  C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (heat & ATP)
• Two mechanisms for synthesis of ATP: Substrate-level phosphorylation and Oxidative phosphorylation
• Cells use ATP to drive endergonic reactions
• Oxidative phosphorylation

  ATP synthase uses energy from a proton gradient formed by high-energy electrons from the oxidation of glucose passing down an electron transport chain. ATP synthase catalyzes the reaction: ADP + Pi → ATP
• NAD+ acquires two electrons and a proton to become NADH. NADH carries the 2 energetic electrons and can supply them to other molecules and reduce them
• Some carriers carry just electrons, some carry electrons and protons
• Structure of NAD+ and NADH: NAD+ serves as an "electron shuttle" during cellular respiration. NAD+ accepts a pair of electrons and a proton from catabolized macromolecules and is reduced to NADH
• Final electron receptor in aerobic respiration is oxygen (O2)
• Free energy in aerobic respiration = -686 kcal/mol of glucose
• Some molecules like phosphoenolpyruvate (PEP) possess a high-energy phosphate bond similar to ATP. When PEP's phosphate group is transferred enzymatically to ADP, the energy in the bond is conserved, and ATP is created
• Anaerobic respiration


  Final electron acceptor is an inorganic molecule (not O2)
• In most organisms, Glycolysis and oxidative phosphorylation are combined. Cells convert glucose and O2 to CO2 and H2O and use the energy released to make ATP. This involves a complex series of oxidation reactions that remove energetic electrons and pass them to an electron transport chain (ETC)
• Ability to supply high-energy electrons is critical to energy metabolism and biosynthesis of many organic molecules, including fats and sugars
• All carriers can be reversibly oxidized and reduced
• Substrate-level phosphorylation


  Transfer phosphate group directly to ADP from another molecule
• Stages of the complete oxidation of glucose

  • Glycolysis
  • Pyruvate oxidation
  • Citric acid cycle
  • Electron transport chain & chemiosmosis
• Glycolysis is a 10-step biochemical pathway that occurs in the cytoplasm