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01 The need for Energy in Living Organisms


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01 The need for Energy in Living Organisms

  1. 1. ENERGY AND RESPIRATIONThe need for energy in living organisms ALBIO9700/2006JK
  2. 2. • Supply of energy: either from the absorption of light energy or from chemical potential energy• Photosynthesis supplies: energy supply and usable carbon compounds• Autotrophs – organisms which can use an inorganic carbon source in the form of carbon dioxide• Heterotrophs – organisms needing a ready- made organic supply of carbon• Organic molecules can be used in 2 ways: – Serve as ‘building bricks’ for making other organic molecules – Represent chemical potential energy released by breaking down molecules in respiration (energy used for work)• Heterotrophs depend on autotrophs for material and energy ALBIO9700/2006JK
  3. 3. • Energy is used for: – The synthesis of complex substances from simpler ones (anabolic reactions) – polypeptides from amino acids – The active transport of substances against a diffusion gradient – sodium-potassium pump – Mechanical work such as muscle contraction and other cellular movements – cilia and flagella, amoeboid movement and vesicles through cytoplasm – Bioluminescence and electrical discharge – Maintaining a constant body temperature (mammals and birds) ALBIO9700/2006JK
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  5. 5. ATP• Structure: – Consists of adenine (organic base) and ribose (pentose sugar) – adenosine (nucleoside) – Combined with 3 phosphate groups (phosphorylated) – Small, water soluble (transported easily) ALBIO9700/2006JK
  6. 6. Adenosine 14.2 kJmol-1 30.5 kJmol-130.5 kJmol-1 ALBIO9700/2006JK
  7. 7. • Energy currency – ATP is the universal intermediary molecule between energy-yielding and energy-requiring reactions used in a cell – Interconversion of ATP and ADP is all-important in providing energy fro the cell • ATP + H2O ↔ ADP + H3PO4 30.5 kJ – The cell’s energy-yielding reactions are linked to ATP synthesis and ATP is used in all forms of work – Excess energy is converted to thermal energy – Energy currency molecule: acts as the immediate donor of energy to the cell’s energy-requiring reactions – Energy storage molecule: is a short-term (glucose or sucrose) or long-term (glycogen, starch or triglyceride) store of chemical potential energy ALBIO9700/2006JK
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  9. 9. • ATP Synthesis: – Energy for ATP synthesis can become available in 2 ways: • Chemical potential energy – glycolysis and Krebs cycle • Electrical potential energy – transfer of electrons by electron carriers in mitochondria and chloroplasts – stored as a difference in H+ concentration across some phospholipid membranes in mitochondria and chloroplasts – H+ are then allowed to flow down concentration gradient through a protein (ATP synthase) – Transfer of 3 H+ allows the production of 1 ATP molecule (ADP and an inorganic phosphate group, Pi, are available inside the organelle) - chemiosmosis – ATP synthase has 3 binding sites and a part of the molecule (γ) that rotates as H+ pass – Produces structural changes in binding sites and allows H+ to pass sequentially through 3 phases: • Binding ADP and Pi • Forming tightly bound ATP • Releasing ATP ALBIO9700/2006JK
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