B4

• Photosynthesis is represented by the equation: carbon dioxide + water light glucose + oxygen
• Photosynthesis


  An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
• Factors affecting the rate of photosynthesis

  • Temperature
  • Light intensity
  • Carbon dioxide concentration
  • Amount of chlorophyll
• Limiting factors are important in the economics of enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while still maintaining profit
• Uses of glucose from photosynthesis

  • Used for respiration
  • Converted into insoluble starch for storage
  • Used to produce fat or oil for storage
  • Used to produce cellulose, which strengthens the cell wall
  • Used to produce amino acids for protein synthesis
• To produce proteins, plants also use nitrate ions that are absorbed from the soil
• Cellular respiration


  An exothermic reaction which is continuously occurring in living cells
• Processes that organisms need energy for

  • Chemical reactions to build larger molecules
  • Movement
  • Keeping warm
• Aerobic respiration is represented by the equation: glucose + oxygen carbon dioxide + water
• Anaerobic respiration in muscles is represented by the equation: glucose lactic acid
• Anaerobic respiration in plant and yeast cells is represented by the equation: glucose ethanol + carbon dioxide
• Anaerobic respiration in yeast cells


  Called fermentation and has economic importance in the manufacture of bread and alcoholic drinks
• During exercise the human body reacts to the increased demand for energy

  Heart rate, breathing rate and breath volume increase to supply the muscles with more oxygenated blood
• If insufficient oxygen is supplied anaerobic respiration takes place in muscles. The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt. During long periods of vigorous activity muscles become fatigued and stop contracting efficiently
• Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose. Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
• Photosynthesis


  1. Takes place in the leaves

  2. Takes place in chloroplasts

  3. Chlorophyll absorbs light energy

  4. Converts carbon dioxide and water into glucose and oxygen
• Photosynthesis is an endothermic reaction, where energy is transferred from the environment to chloroplasts by light
• Carbon dioxide and water supply for photosynthesis

  1. Carbon dioxide diffuses into leaves through stomata

  2. Water is taken up from soil by roots and transported to leaves via xylem
• Products of photosynthesis


  • Glucose is the main product
  • Oxygen is also produced but not as important
• Uses of glucose produced by photosynthesis

  • Cellular respiration
  • Making cellulose
  • Making starch
  • Making amino acids
  • Making oils and fats
• Plant growth rate is often dependent on the rate of photosynthesis
• Factors affecting the rate of photosynthesis are light intensity, temperature, carbon dioxide concentration, and the amount of chlorophyll
• Factors affecting photosynthesis


  • Light intensity
  • Temperature
  • Concentration of carbon dioxide in the air
  • Amount of chlorophyll that the plants have
• Chlorophyll


  The pigment within chloroplasts that absorbs the light energy needed for photosynthesis
• Plants have less chlorophyll


  They won't be able to carry out as much photosynthesis
• Factors that can reduce chlorophyll levels

  • Disease (e.g. tobacco mosaic virus)
  • Environmental stress
  • Lack of nutrients (e.g. water)
• Limiting factors for photosynthesis are normally light, carbon dioxide and temperature
• Graphing limiting factors for photosynthesis

  1. Plot light intensity on x-axis

  2. Plot rate of photosynthesis on y-axis
• As light intensity increases

  Rate of photosynthesis increases
• The line flattens out when something else becomes the limiting factor, such as carbon dioxide concentrations or temperature
• As carbon dioxide concentration increases

  Rate of photosynthesis increases
• As temperature increases


  Rate of photosynthesis increases initially, then starts to drop as enzymes denature
• Anything beyond 45 degrees, the enzymes are fully denatured and the rate of reaction falls to zero
• Graphs can show multiple limiting factors, by comparing curves at different conditions
• Farmers creating conditions to increase photosynthesis

  • Using greenhouses to trap heat and provide artificial light
  • Pumping in carbon dioxide
  • Using paraffin heaters for heat and CO2
  • Applying fertilizers for essential minerals
  • Using pesticides to control pests
• Creating optimal conditions for photosynthesis can be costly for farmers, so they have to weigh the extra cost against the expected yield increase
• Cellular respiration


  An exothermic reaction which transfers energy from glucose and is continuously occurring in living cells
• Cellular respiration


  Breaking apart glucose molecules to release the energy that's trapped inside
• How organisms use their energy

  • Building up larger molecules from smaller ones (e.g. combining amino acids to form proteins)
  • Muscular contraction for movement
  • Maintaining body temperature
• Energy is needed for loads of reactions in our cells, most of which are catalyzed by enzymes