Bio energetic

• Plants are autotrophs – this means that they can make their own food using light, water and carbon dioxide
• Photosynthesis is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
• The leaves of the plant are where most photosynthesis takes place, in specialised mesophyll cells which are packed with chloroplasts containing chlorophyll to absorb as much light energy as possible
• Cellular respiration is an exothermic reaction which is continuously occurring in living cells
• Word equation for photosynthesis

  Carbon dioxide + Water → Glucose + Oxygen
• Cellular respiration


  The chemical process that releases energy
• Reactants for photosynthesis obtained by a plant

  • Light
  • Water
  • Carbon dioxide
• Organisms need energy for

  • Chemical reactions to build larger molecules from smaller molecules
  • Muscle contraction to allow movement
  • Keeping warm (to maintain a constant temperature suitable for enzyme activity)
• Water is not considered a limiting factor as the amount needed is relatively small compared to the amount of water transpired from a plant so there is hardly ever a situation where there is not enough water for photosynthesis
• Aerobic respiration


  Glucose is reacted with oxygen
• Temperature


  • Affects the kinetic energy of particles, increasing temperature increases the likelihood of collisions between reactants and enzymes
  • At higher temperatures, enzymes that control the processes of photosynthesis can be denatured

  
• Aerobic respiration


  Respiration in cells that takes place using oxygen
• As temperature increases


  The rate of photosynthesis increases
• Anaerobic respiration in animals

  Incomplete breakdown of glucose into lactic acid
• Anaerobic respiration


  Respiration in cells that takes place without oxygen
• As light intensity increases

  The rate of photosynthesis increases
• Anaerobic respiration in plants & yeast

  Breaking down glucose in the absence of oxygen to produce ethanol and carbon dioxide
• As carbon dioxide concentration increases

  The rate of photosynthesis increases
• Fermentation


  Anaerobic respiration in yeast cells
• Chlorophyll


  The pigment in chloroplasts that absorbs light energy for photosynthesis
• Differences between anaerobic and aerobic respiration

  • Need for oxygen
  • Products
  • Relative amounts of energy transferred
• The amount of chlorophyll can be affected by diseases, lack of nutrients, and loss of leaves
• Exercising increases muscle contractions

  Greater energy demand, requiring greater supply of oxygen for aerobic respiration
• More than one limiting factor can affect the rate of photosynthesis
• Body's reactions to increased oxygen demand during exercise

  1. Breathing rate and breath volume increase

  2. Heart rate increases
• Inverse square law


  Light intensity and distance are inversely proportional, as distance doubles the light intensity decreases by a factor of 4
• Vigorous exercise cannot be met by oxygen supply


  Some energy supplied by anaerobic respiration, resulting in lactic acid formation
• Commercial horticulturists grow plants in greenhouses to control limiting factors and maximise the rate of photosynthesis
• Oxygen debt


  Extra oxygen needed after exercise to react with lactic acid produced via anaerobic respiration
• Investigating photosynthesis rate


  1. Place pondweed in water

  2. Use a light source at different distances

  3. Record number of oxygen bubbles produced in 3 minutes

  4. Repeat for different distances

  5. Plot graph of distance vs bubbles per minute
• How body deals with lactic acid

  1. Oxidised to form carbon dioxide and water

  2. Transported to liver and converted back into glucose
• Uses of glucose from photosynthesis

  • Respiration
  • Conversion to starch for storage
  • Production of fat or oil
  • Production of cellulose
  • Synthesis of amino acids and proteins
• Metabolism


  The sum of all the reactions in a cell or the body
• A test to show a plant is photosynthesising is to test the leaf for the presence of starch using iodine
• Enzymes


  • Control all the reactions occurring in cells
  • Products of one reaction are often the reactants for another
• Metabolic substrates


  • Sugars
  • Amino acids
  • Fatty acids
  • Glycerol
• The products of digestion are used to build substances, and some of these are then broken down - this is metabolism
• Metabolism includes conversion of glucose to cellulose, glycogen, lipids, amino acids, and breakdown of excess proteins