bioenergetics

• How can we artificially keep temperature at the ideal level?

  By growing plants in a greenhouse, which can trap the sun's heat, and so make sure that temperature is not a limiting factor. We can also use a heater during winter to keep the temperature at the ideal level. However, if it gets too hot during the summer, you can use shade and ventilation to cool things down.
• What is photosynthesis?


  The endothermic reaction where plants use sunlight to synthesise glucose (which has energy stored in it as chemical bonds) from carbon dioxide and water.

  Energy is transferred from the environment to the chloroplasts by light.
• Where does photosynthesis occur?

  Chloroplasts in the leaves in the palisade mesophyll
• What is the name of the green pigment in chloroplasts that absorbs the light?

  Chlorophyll
• What is the word equation for photosynthesis?

  Carbon dioxide + water --> glucose + oxygen
• What is the symbol equation for photosynthesis?

  6CO2 + 6H2O --> C6H12O6 + 6O2
• Is photosynthesis an exothermic or endothermic reaction?

  Endothermic, because energy is transferred from the environment to the chloroplasts by light.
• What is one thing that the glucose is used for?

  Respiration, which transfers energy from glucose.
• What is another thing that the glucose is used for?

  It is converted into cellulose, which strengthens the plant cell wall.
• What is another thing that the glucose is used for?

  It is used to produce fat or oil for storage.
• What is another thing that the glucose is used for?

  It is combined with nitrate ions that are absorbed from the soil to make amino acids, which are then made into proteins.
• What is one final thing that the glucose is used for?

  It is turned into starch and stored in roots, stems and leaves, ready for when photosynthesis isn't happening, like in the winter.
• List the four uses of glucose

  - cellulose

  - starch

  - combined with nitrate ions = amino acids

  - fat + oils
• Why is starch better to be stored than glucose?

  Because starch is insoluble - a cell with lots of glucose would draw in lots of water and swell up.
• Describe how glucose from the small intestine is moved to a muscle cell.

  glucose is absorbed by diffusion into the bloodstream

  blood delivers glucose to muscles in capillaries
• What is a limiting factor?


  A factor that prevents the rate of photosynthesis from increasing.
• Give the four factors limiting photosynthesis

  Light intensity, CO2 concentration, temperature and number of chlorophyll in the leaves
• For example, what would be the limiting factor on a cloudy day?

  Light intensity
• What does the graph showing how light intensity affects the rate of photosynthesis look like?

  
• Why does the graph look like this?

  The greater the light intensity, the higher the rate of photosynthesis, as there is more energy for photosynthesis to occur. However, about a certain light intensity, the rate levels. Increasing the light intensity has no effect as there is now a new limiting factor.
• What does the graph showing how levels of carbon dioxide affect the rate of photosynthesis look like?

  
• Why does the graph look like this?

  The higher the levels of CO2, the higher the rate of photosynthesis, as more CO2 means an increased amount of substrate, leading to a higher rate of photosynthesis. However, above a certain level of CO2, there is another limiting factor, so increasing the CO2 levels will have no effect.
• What does the graph showing how temperature affects the rate of photosynthesis look like?

  
• Why does the graph look like this?

  Because photosynthesis is an enzyme-controlled reaction. This means that as the temperature increases, the rate also increases, as higher temperatures give the enzymes more kinetic energy, leading to more frequent successful collisions. However, after a certain temperature, the enzymes begin to denature, causing the rate of photosynthesis to rapidly decrease.
• What is the inverse square law?

  The light intensity is directly proportional to one over the distance squared. Distance doubled = light intensity falls by 4 times
• What is the equation for the inverse square law?

  Light Intensity = 1 / distance squared
• What benefits does keeping plants in greenhouses provide?

  It is an artificial means of increasing the rate of photosynthesis which would increase yield and profit

  It makes it easier to keep the plants from pests and diseases.
• How can we artificially make sure light intensity isn't a limiting factor?

  By supplying artificial light after the sun goes down.
• How can we artificially make sure carbon dioxide levels are not a limiting factor?


  By using a paraffin heater/ oil burner, because as the paraffin burns, it makes carbon dioxide as a by-product. It provides both heat and CO2
• Why is it important that a farmer supplies just the right amount of heat, light etc?


  The extra cost of working a greenhouse needs to be justified by the profits. Excess heat and light will waste money.
• What is respiration?


  The chemical reaction that provides energy for organisms to function.
• Is respiration an exothermic or endothermic reaction?

  Exothermic
• What is one thing that the energy is used for?

  Maintenance of internal body temperature
• What is another thing that the energy is used for?

  Muscle contraction
• What is one final thing that the energy is used for?

  Synthesis reactions - chemical reactions to build larger molecules or to break larger molecules into smaller ones. E.g. protein synthesis from amino acids
• What is the word equation for aerobic respiration?

  Glucose + oxygen --> carbon dioxide + water + (energy)
• What is the symbol equation for aerobic respiration?

  C6H12O6 + 6O2 --> 6CO2 + 6H2O
• How much energy does aerobic respiration release?

  38 ATP because the glucose has been fully oxidised
• In which organelle does aerobic respiration occur?

  Mitochondria
• What is anaerobic respiration?

  The incomplete breakdown of glucose, which occurs during strenuous exercise in the absence of oxygen.