cell requirements

• All cells require a form of energy for life's processes such as movement, synthesis and maintaining an internal environment
• Autotrophs


  Can convert inorganic materials into organic molecules using light energy in the process called photosynthesis

  
• Heterotrophs


  Need to feed on matter containing organic molecules to provide energy and essential materials for growth and life's processes
• Three important chemical reactions involved in energy changes in organisms

  1. Photosynthesis

  2. Aerobic respiration

  3. Fermentation (in both plants and animals)

  
• Material requirements for autotrophs and heterotrophs

  • Gases
  • Minerals
• Metabolic wastes


  Byproduct of biochemical reactions in cells, need to be excreted from cells and from the body of multicellular organisms to avoid poisoning other cells
• Energy cannot be created or destroyed, it can only be transferred or transformed
• Energy


  • Chemical energy - energy stored within chemical bonds of molecules
  • Radiant (light) energy
  • Thermal (heat) energy - caused by the movement of atoms within a substance
  • Kinetic (movement) energy
• Light energy is transformed into chemical energy in cells performing photosynthesis


  Life stops without continued input of energy
• Chemical reactions in cells

  Require an energy 'push' or activation energy to start, enzymes lower the activation energy required
• Energy in the circle of life

  1. Radiant energy is captured by photo-autotrophs (producers)

  2. Autotrophs create their own energy

  3. Producers are consumed by photo-heterotrophs (consumers)

  4. Heterotrophs gain their energy from another source
• ATP


  Adenosine triphosphate - active and ready for release energy for cell use

  
• ADP


  Adenosine diphosphate - inactive and needs another phosphate (Pi)
• ATP breaks down to form ADP and Pi


  Releasing a constant amount of free energy that is available for cellular use
• Some energy released from aerobic respiration (about 40%) is used to drive the conversion (or synthesis) of ADP and Pi to ATP

  
• Energy not transferred in this way (about 60%) is 'lost' from the cell as heat energy (helping us to maintain a temperature of 37°C)
• ATP can be regenerated very quickly, and as it is soluble, can be transported readily throughout the cell to where it is required
• Photosynthesis


  1. 6CO2 + 6H2O → (light and chlorophyll) → C6H12O6 + 6O2

  2. Carbon dioxide + Water → (light and chlorophyll) → Glucose + Oxygen

  
• Autotrophs convert inorganic molecules materials into organic molecules
• Photosynthesis requires light energy and occurs at the grana (stacks of membranes) in the chloroplast

  
• Aerobic respiration


  1. C6H12O6 + 6O2 → 6CO2 + 6H2O

  2. Glucose + Oxygen → Carbon dioxide + Water

  
• Aerobic respiration occurs when oxygen is available, starts in the cytosol and is completed within the mitochondria
• 1 glucose molecule will produce 36 ATP molecules in aerobic respiration

  
• Fermentation (in both plants and animals)

  1. in plants and yeast: C6H12O6 → 2C2H5OH + 2CO2

  2. Glucose → Ethanol and Carbon dioxide

  3. in animals: C6H12O6 → 2C3H6O3

  4. Glucose → Lactic acid
• Anaerobic respiration (fermentation) occurs in the absence of oxygen, solely in the cytosol
• Anaerobic respiration creates 2 ATP molecules from 1 glucose molecule

  
• Alcohol fermentation


  Occurs in yeast and some plants, ethanol is a waste product
• Lactic acid fermentation


  Occurs in animal cells when oxygen levels decline during strenuous exercise, lactic acid is a waste product
• Material requirements for cells

  • Nitrogen
  • Phosphorus
  • Magnesium
  • Sodium
  • Cobalt
  • Iron
• Metabolic wastes


  Removal of these wastes is called excretion, can occur through passive and active forms of transport
• Carbon dioxide is toxic within our bodies, causing our blood to become acidic, it is excreted through the respiratory system and controls our respiratory rate