Biology 4

• Photosynthesis


  Process that uses energy to change carbon dioxide and water into glucose and oxygen
• Photosynthesis


  • Endothermic- energy is transferred from the environment
  • Takes place in chloroplasts
  • Chloroplasts contain pigments like chlorophyll that absorb light
• Respiration


  The process that changes energy from glucose into a form that enables the plants to convert the rest of the glucose into various other useful substances
• Making cellulose


  Glucose is converted into cellulose for making strong plant cell walls
• Making amino acids


  Glucose is combined with nitrate ions (food from the soil) to make amino acids, which are then made into protein
• Storing as oils or fats

  Glucose is turned into lipids (oils and fats) for storing in seeds
• Storing as starch


  1. Glucose is converted into starch and stored in roots, stems and leaves, ready for use when photosynthesis isn't happening, like in the winter

  2. Starch is insoluble, which makes it much better for storing than glucose

  3. A cell containing lots of glucose would draw in lots of water by osmosis
• Ideal conditions for photosynthesis

  The most common way to artificially create the ideal environment for plants is to grow them in a greenhouse
• Greenhouses


  1. Help to trap the Sun's heat

  2. Make sure the temperature doesn't become limiting

  3. In winter, a farmer or gardener might use a heater to keep the temperature at the ideal level

  4. In summer, they might use shades and ventilation to cool things down
• Commercial growers


  Can supply artificial light after the sun goes down to give their plants more quality photosynthesis
• Farmers and gardeners


  1. Can increase the level of CO2 in the greenhouse

  2. A fairly common way is to use a paraffin heater to heat the greenhouse, as the paraffin burns it makes CO2 as a by-product
• Rate of photosynthesis affected by:

  1. Light
  2. Co2 concentration
  3. Temperature
  4. Chlorophyll
• Aerobic respiration


  Respiration using oxygen, the most efficient way to transfer energy from glucose to supply all energy needed for living processes
• Aerobic respiration takes place in the mitochondria in plants and animals
• The chemical equation for aerobic respiration is: C6H12O6 + 6O2 → 6CO2 + 6H2O
• Anaerobic respiration


  Respiration without oxygen
• Anaerobic respiration


  1. Incomplete breakdown of glucose

  2. Producing lactic acid
• Anaerobic respiration


  Doesn't produce as much energy as aerobic respiration
• Anaerobic respiration


  • Glucose isn't fully oxidised (doesn't combine with oxygen)
  • Only useful in emergencies e.g. during exercise when it allows you to keep using your muscles for a little longer
• Anaerobic respiration


  Respiration that occurs without oxygen
• Plants and yeast cells can respire without oxygen
• Plants and yeast cells produce ethanol (alcohol) and carbon dioxide instead of lactic acid during anaerobic respiration
• Fermentation by yeast


  • Used to make bread and alcoholic drinks e.g. beer and wine
• Bread making


  Carbon dioxide from fermentation causes the dough to rise
• Beer and wine making

  Fermentation process produces alcohol
• Anaerobic respiration in yeast


  1. Glucose

  2. Ethanol + Carbon dioxide
• Respiration is exothermic
• Muscles need energy from respiration to contract
• When you exercise


  Some of your muscles contract more than normal
• Muscles contracting more than normal

  You need more energy
• Needing more energy

  Comes from increased respiration
• The increased oxygen in your cells means you need to get more oxygen into them
• To get more oxygen into the blood

  1. Breathing rate and breath volume increase

  2. Heart rate increases to get the oxygenated blood around the body faster
• Increased heart rate


  Removes CO2 faster
• Long periods of exercise cause muscle fatigue - the muscles get tired and stop contracting efficiently
• Oxygen debt


  The extra amount of oxygen your body needs to react all the build up of lactic acid and remove it from the cells
• Oxygen debt


  1. Oxygen reacts with the lactic acid to convert it to harmless CO₂ and water

  2. You have to repay the oxygen that you didn't get to your muscles in time, because the lungs, heart and blood couldn't keep up

  3. You have to take deep breaths during exercise to get more oxygen into your blood, which is constricted
• There are high levels of lactic acid

  The pulse and breathing rate stay high
• Removing lactic acid


  Blood transports the lactic acid to the liver where it is converted back to glucose
• Reactions where larger molecules are broken down into smaller ones


  1. Glucose is broken down in respiration

  2. Excess protein is broken down to produce urea