Control Systems, Cell Metabolism & respiration - Biology Unit 3 Edexcel b3

Control Systems, Cell Metabolism & respiration - Biology Unit 3 Edexcel b3

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  • Created by: Elouise
  • Created on: 02-04-12 09:57

Cell Metabolism - Energetically favourable or unfa

  • Necessary because organisms are constantly undergoing cellular changes, they are not in a state of equilibrium
  • An attempt to regulate celular conditions by making internal changes to mainain a steady cellular state.
  • Disorderly conditions are energetically favourable; they release energy. Highly ordered and organised conditions are not energetically favourable and require energy to occur.
  • The body produces the energy by breaking down ATP then using the energy to promote energetically unfavourable but bioglogically necessary reactions.
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Cell Metabolism 2 - Phototrophs & Chemotrophs

  • Cells need an external energy source.
  • Phototrophs (eg plants) get their energy from the sun through photosynthesis. They use light energy to convert Carbon Dioxide and water into carbohydrates and Oxygen.
  • Chemotrophs (eg humans) get their energy from the breakdown of organic compounds such as carbohydrates and proteins. 
  • The relationship between Chemotrophs and Phototrophs is complimentary: Chemotrophs need oxygen and expire carbon dioxide, phototrophs need carbon dioxide and expire oxygen.
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Cell Metabolism 3 - Metabolic Pathways

  • Two major pathways - one involves degradation reactions the other involves synthesis reactions
  • Catabolic pathways involve the breakdown of ingested food moleculesBreak down in carbohydrates & proteins into their polysaccharide, or sugar, and amino acid subunits. These reactions release energy.
  • Anabolic pathways involve the synthesis of essential biomolecules. Take the simple products of catabolic degradation eg ATP and use energy from their degradation to synthesise complex biomolecules.
  • Enzymes work in combination with each of these pathways.
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Cell Metabolism 4 - ATP

  • The breakdown of ATP is energetically favourable
  • It involves splitting one larger, more organised molecule into two smaller ones. 
  • The energy released can be used to drive another less favourable reaction.
  • ATP is a major source of energy for cells.
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