topic 4- bioenergetics

• what does photosynthesis produce


  glucose using light
• where does photosynthesis take place

  in chloroplasts
• how is energy transferred to the chloroplasts

  by light
• what type of reaction is photosynthesis

  endothermic
• what is word equation for photosynthesis

  carbon dioxide + water -----> glucose + oxygen
• what is symbol equation for photosynthesis

  6co2 +6h2o ----> c6h12o6 +6o2
• What plants use glucose for

  1. Respiration - transfers energy from glucose which enables plants to convert the rest of the glucose into various other substances

  2. Cellulose - glucose is converted into cellulose to make strong cell walls

  3. Amino acids - glucose is combined with nitrate ion to make amino acids, which are then made into proteins

  4. Stored as oil or fats - glucose is turned into lipids (oils or fats) for storing in seeds

  5. Stored as starch - glucose is turned into starch and stored in roots, stems and leaves, ready for when photosynthesis isn't happening, like in the winter. Starch is insoluble, which makes it better for storing than glucose
• what limiting factors affect the rate of photosynthesis

  intensity of light- at night there is a lack of light

  concentration of co2- if its warm and bright enough the amount of co2 is usually limiting

  temperature - in winter its normally colder

  chlorophyll- the amount of chlorophyll in a plant can be affected by disease or environmental stress, such as lack of nutrients. these factors cause chloroplasts to become damaged or to not make enough chlorophyll. this means they cannot absorb as much light
• light provides energy needed for photosynthesis- as the light level increase so does the rate of photosynthesis, but only up to a certain point. this is because the temperature of co2 will be a limiting factor
• what is the inverse square law

  the inverse square law is light intensity is proportional to 1/ distance squared

  it means that if you halve the distance the light intensity will be 4 times greater, or if you third the distance the light intensity will be 9 times greater and etc
• why are greenhouses helpful to let plants grow

  because they help trap the suns heat, making sure temperature doesn't become limiting, in winter a heater can be used , they often supply artificial light after sun goes down, and the gardener often increases the level of co2 in the greenhouse.

  it also helps keep plants away from pests and disease

  however it does cost a lot of money
• energy is transferred by respiration
• respiration is the process of transferring energy from glucose, which goes on in every cell
• all living things respire- its how they transfer energy from food to cells
• respiration is exothermic- it transfers energy to the environment
• how do organisms use energy transferred by respiration


  to build up larger molecules from smaller ones

  in muscles it helps them contract

  in mammals and birds the energy is used to keep there body temperature steady in colder surroundings
• metabolism is all the chemical reactions in an organism
• chemical reactions are controlled by enzymes
• aerobic respiration is the respiration using oxygen- its the most efficient way to transfer energy from glucose
• where do most of the reactions in aerobic respiration happen


  in the mitochondria
• what is the word equation for aerobic respiration

  glucose +oxygen ---> carbon dioxide + water
• what is symbol equation for aerobic respiration


  c6h12o6 + 6o2 ----> 6co2 + 6h2o
• anaerobic respiration is used if there is not enough oxygen
• what is the word equation for anaerobic respiration in muscle cells

  glucose ----> lactic acid
• why doesn't anaerobic respiration transfer as much energy as aerobic 


  because glucose is not fully oxidised
• what is fermentation

  anaerobic respiration in yeast cells
• plant and yeast cells can respire without oxygen, but they produce ethanol and carbon dioxide instead of lactic acid
• when you exercise you respire more
• when doing exercise why do your breathing rate and breath volume rate increase

  to get more oxygen into your blood
• when doing exercise why does your heart rate increase

  to get oxygenated blood around the body faster
• what is oxygen debt


  the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from your cells