bioenergetics

• Using glucose in plants - respiration


  Transfers energy from glucose which enables the plant to convert the rest of the glucose into various other useful substances
• Using glucose in plants - making cellulose

  Glucose is converted into cellulose for making strong cell walls
• Using glucose in plants - making amino acids


  Glucose is combined with nitrate ions to make amino acids, which are then made into proteins
• Using glucose in plants - stored as oils or fats


  Glucose is turned into lipids for storing in seeds
• Using glucose in plants - stored as starch

  Glucose is turned into starch and stored in roots, stems and leaves ready for use when photosynthesis isn't happening, like in the winter. Starch is insoluble, which makes it better for storing than glucose - a cell wall containing lots of glucose would draw in lots of water and swell up
• When is light the limiting factor?

  Night time
• When is temperature the limiting factor?


  Winter
• When is the carbon dioxide concentration the limiting factor?

  When it's warm and bright enough
• Limiting factors - light intensity


  As the light intensity increases, the rate of photosynthesis increases steadily

  
• Limiting factors - carbon dioxide concentration


  As the concentration of carbon dioxide increases, the rate of photosynthesis increases steadily

  
• Limiting factors - temperature

  If the temperature gets too high, the enzymes will denature - 45 degrees

  If the temperature is too low, the enzymes will work very slowly

  
• What is light intensity inversely proportional to?


  Distance²
• Greenhouses - temperature

  Help to trap the sun's heat and ensure the temperature doesn't become a limiting factor

  Heaters are used in winter to maintain a high temperature

  Ventilation is used in summer to prevent the temperature increasing too much
• Greenhouses - light intensity

  Artificial light is used after the sun goes down - gives the plant more quality photosynthesis time
• Greenhouses - carbon dioxide concentration

  Paraffin heaters help increase the concentration of carbon dioxide - as the paraffin burns, it creates carbon dioxide as a by-product
• Other benefits of greenhouses

  1) Easier to keep the plants free from pests

  2) Fertilisers help provide all the minerals needed for healthy growth
• What is respiration?


  The process of transferring energy from glucose which goes on in every cell
• Is photosynthesis endothermic or exothermic?

  Endothermic - energy is transferred from the environment
• Is respiration endothermic or exothermic?

  Exothermic - transfers energy to the environment
• How do organisms use the energy transferred by respiration?

  1) To build up larger molecules from smaller ones e.g. proteins from amino acids

  2) In animals, it's used to allow the muscles to contract

  3) In mammals and birds, the energy is used to keep their body temperature steady in colder surroundings
• Aerobic respiration


  Respiration using oxygen

  Goes on constantly in plants and animals

  Most of the reactions happen inside mitochondria
• Aerobic respiration equation

  Glucose + oxygen --> carbon dioxide + water
• Anaerobic respiration - animals

  Respiration without oxygen

  Incomplete breakdown of glucose

  Happens when your body can't supply enough oxygen to your muscles during vigorous exercise

  Doesn't transfer as much energy as aerobic respiration - glucose isn't fully oxidised
• Anaerobic respiration equation - animals

  Glucose --> lactic acid
• Anaerobic respiration - plants & yeasts

  In yeasts, it's called fermentation

  Fermentation is used to make bread and alcohol drinks
• Anaerobic respiration equation - plants and yeasts

  Glucose --> ethanol + carbon dioxide
• What three things increase with increased respiration?

  1) Breathing rate

  2) Breath volume

  3) Heart rate
• What happens during increased respiration?

  More oxygen diffuses into the blood which causes carbon dioxide to be removed more quickly
• What does anaerobic respiration lead to?

  Oxygen debt - the amount of extra oxygen in your body needs to react with the build up of lactic acid and remove it from the cells
• What forms when oxygen reacts with lactic acid?

  Carbon dioxide and water
• How else does the body cope with a high level of lactic acid?


  The blood that enters your muscles transports the lactic acid to the liver. Here, the lactic acid is converted back to glucose
• Oxygen Production - Method

  1) A source of white light is placed at a specific distance from the pondweed

  2) The pondweed is left to photosynthesise for a set amount of time. As it photosynthesises, the oxygen released will collect in a capillary tube

  3) At the end of the experiment, the syringe is used to draw the gas bubble in the tube up alongside a ruler & the length of the gas bubble is measured. This is proportional to the volume of O2 produced

  4) Any variable that could affect the results should be controlled

  5) The experiment is repeated twice with the light source at the same distance & the mean volume of O2 produced is calculated

  6) Then, the whole experiment is repeated with the light source at different distances from the pondweed
• What are lipid molecules made up of?

  One molecule of glycerol & three fatty acids
• What is metabolism?

  The sum of all the reactions that happen in a cell or in the body
• What is muscle fatigue?

  When over long periods of exercise, the muscles get tired & stop contracting efficiently