Unit 4: bioenergetics

• Photosynthesis


  The process by which plants make glucose from sunlight
• Endothermic reaction


  Energy is transferred from the environment to the chloroplasts by light
• Photosynthesis


  Carbon dioxide + water → glucose + oxygen
• Factors affecting rate of photosynthesis

  • Temperature
  • Light intensity
  • Carbon dioxide concentration
  • Amount of chlorophyll
• Measuring oxygen production to calculate rate of photosynthesis

  1. Pondweed in test tube

  2. Capillary tube and syringe

  3. Lamp at measured distance

  4. Measure distance bubble moves to calculate oxygen volume

  5. Control variables except independent variable
• Limiting factor


  An environmental condition (such as light intensity) which, in low levels, restricts any increase in the rate of photosynthesis
• Light intensity


  Inversely proportional to the square of the distance (inverse square law)
• Uses of glucose from photosynthesis

  • For respiration
  • Converted into insoluble starch for storage
  • To produce fat or oil for storage
  • To produce cellulose to strengthen cell walls
  • Combined with nitrates to form amino acids which produce proteins
• Respiration


  The process of transferring energy from glucose so living processes can occur
• Exothermic


  Energy is transferred to the environment
• Types of respiration


  • Aerobic (with oxygen)
  • Anaerobic (without oxygen)
• Anaerobic respiration in animals

  Glucose → Lactic acid
• Anaerobic respiration in plants and yeast

  Glucose → Ethanol + Carbon dioxide
• Oxygen debt


  The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
• Metabolism


  The sum of all the reactions in a cell or the body, controlled by enzymes
• Metabolic reactions


  • Glucose to starch, glycogen and cellulose
  • Glycerol and fatty acids to lipids
  • Glucose and nitrate to amino acids and proteins
  • Respiration reactions
  • Urea formation from protein breakdown
• Photosynthesis

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

  1. Takes place in chloroplasts

  2. Chloroplasts contain pigments like chlorophyll

  3. Energy is transferred to the chloroplasts from the environment by light

  4. Photosynthesis is endothermic - energy is transferred from the environment in the process

  5. Equation: carbon dioxide + water → glucose + oxygen
• Ways plants use glucose

  • Respiration
  • Making cellulose
  • Making amino acids
  • Stored as oils or fats
  • Stored as starch
• Limiting factors

  • Intensity of light
  • Concentration of CO2
  • Temperature
  • Chlorophyll
• Limiting factor

  Stops photosynthesis from happening any faster
• Light intensity

  Increases rate of photosynthesis up to a point, then no further increase
• CO2 concentration

  Increases rate of photosynthesis up to a point, then no further increase
• Temperature

  Increases rate of photosynthesis up to an optimal point, then decreases as enzymes are destroyed
• Measuring rate of photosynthesis using oxygen production

  1. Place light source at varying distances from pondweed

  2. Measure volume of oxygen gas produced

  3. Repeat experiment with different light intensities, CO2 concentrations, or temperatures
• Inverse square law

  Light intensity decreases proportionally to the square of the distance
• Greenhouses help control temperature, light, and CO2 to create ideal conditions for plant growth
• Farmers and gardeners can supply additional light, heat, CO2, and nutrients in greenhouses to maximise plant growth
• Light is always needed for photosynthesis, so commercial formers often supply light after the Sun goes down to give their plants more quality photosynthesis time
• Famers and gardeners can also increase the level of carbon dioxide in the greenhouse to help the plants grow
• Keeping plants need in a greenhouse also makes it easier to keep them free from pests
• Sorting all this out costs money-but if the farmer can keep the conditions just right the plants will grow much feacher and a decent crop can be harvested much more quickly
• It's important that a farmer supplies just the right amount of heat, light, etc.-not too much or the plants will die, as this would just be wasting
• An experiment was carried out to find out the effect of temperature on the rate of photosynthesis
• Variables that should have been controlled in this experiment

  • 2 variables
• A plant is moved from 15 cm away from its light source to 5 cm away from its light source

  The light intensity becomes nine times greater
• Respiration is NOT "Breathing In and Out"
• Respiration

  The process of transferring energy from glucose
• Respiration transfers energy for all kinds of things
• How animals use the energy transferred by respiration

  • To build up larger molecules from smaller ones
  • To allow muscles to contract (so they can move about)
  • To keep their body temperature regulated in colder surroundings