(4)Bioenergetics

• What is photosynthesis?

  Process by which plants use energy to convert carbon dioxide; water into glucose and oxygen
• What type of reaction is photosynthesis?

  Endothermic- energy is transferred from environment to chloroplasts by light
• Photosynthesis word and symbol equation?

  Carbon dioxide + water (light)→ glucose + oxygen

  6CO2 + 6H2O + light energy → C6H12O6 + 6O2
• 5 uses of glucose?

  1. Respiration (transfers energy from glucose enabling plant to convert glucose into other useful substances
  2. Making Cellulose (makes plant cell wall strong)
  3. Making amino acids (Combined with nitrate ions from soil,this makes proteins)
  4. Stored as fats or oils (lipids- energy stored in seeds)
  5. Stored as insoluble starch ( better storage used in night/winter when photosynthesis not happening)
• What happens if plant has lots of glucose?

  Draws in lots of water and swell up
• What are the 4 limiting factors for photosynthesis?

  • Light intensity
  • Temperature
  • CO2 concentration
  • Chlorophyll amount
• What is meant by limiting factor?

  A factor which prevents a reaction from happening any faster
• How is the amount of chlorophyll a limiting factor?

  Amount of chlorophyll can be affected by disease like TMV or lack of nutrients this causes chloroplasts to be damaged or not make enough chlorophyll so not as much light absorbed so lower photosynthesis rate
• How does light intensity affect photosynthesis?

  1. When light intensity is 0, photosynthesis rate is 0
  2. As light increases, photosynthesis rate increases as more light so faster reaction (rise on graph means that light is limiting factor)
  3. When rate of photosynthesis doesn't Increase graph levels off, meaning light intensity is no longer the limiting factor and something else is
• How does CO2 concentration affect photosynthesis?

  1. As co2 level increases, photosynthesis rate increases(rise on graph means co2 is limiting factor)
  2. When rate of photosynthesis doesn't increase, co2 is no longer the limiting factor and something else is
• What does patchy leaves mean?

  They trap less light energy than normal leaves so they have a lower rate of photosynthesis due to not that much chlorophyll
• How does temperature affect rate of photosynthesis?

  1. As we increase temperature, enzymes involved will work faster so the photosynthesis rate increases(graph rises)
  2. If temperature is too high(45C), enzymes will denature and rate of photosynthesis falls. (graph falls)
• Explain a photosynthesis graph with light intesity but with 2 different temperatures

  1. Both of the lines show light intensity increases, rate of photosynthesis increases steadily
  2. Lines level off when light no longer limiting factor. Line at 25C, levels off at a higher point than one at 15C, showing temperature was a limiting factor at 15C
• Explain a photosynthesis graph with light intensity but same temperature and different CO2 conc

  1. Graph shows photosynthesis affected by light intensity and CO2 conc
  2. Both lines level off when light no longer limiting factor
  3. Line at higher CO2 conc levels off at a higher point than lower CO2 conc.This means CO2 was limiting factor at the lower level conc. Limiting factor IS NOT temperature
• What method to artificially create ideal conditions for farming?

  Greenhouses. This increases the rate of photosynthesis as it increases yield of crops produced. It traps the sun heat and can use heaters and ventilation for ideal temperature
• Importance of economics with greenhouse?

  If farmer keeps conditions just right for photosynthesis, plants will grow faster and decent crop harvested more often to be sold. Important that right amount heat,light,etc as you want enough for plant to grow but not more than plants need
• Benefit of parafin heater and oil heater?

  Releases heat and carbon dioxide at the same time
• RP6: Photosynthesis, effect of light using pondweed

  1. Take a boiling tube and place it 10cm away from LED light/ place beaker with water
  2. Fill boiling tube with sodium hydrogen carbonate solution
  3. Put piece of pondweed in boling tube with cut end at top
  4. Leave for 5 minutes to acclimatise to conditions in boiling tube
  5. Use stop watch and count bubble produced in 1minute
  6. Repeat 2 more times to calculate mean bubbles in 1 min
  7. Do experiment again from start at 20,30,40cm
• Why is LED light used in RP6

  It doesn't release very much heat, as too much heat can change temperature of experiment
• What happens if we use a normal lightbulb?

  Place a beaker of water between light and boiling tube as this absorbs heat produced by bulb
• Why use sodium hydrogen carbonate solution?

  It releases CO2, which is needed for photosynthesis
• What are the bubbles of gas produced?

  Oxygen that is produced by photosynthesis
• What are the 2 main problems with RP6?

  • Number of bubbles too fast to count accurately
  • Bubbles are not the same size, a large bubble would be the same as a small bubble
• How to counteract with RP6 problems?

  Measure the volume of oxygen instead of bubble produced.

  Add: place pondweed under funnel and catch bubbles in measuring cylinder. Use measuring cylinder with water to measure volume of oxygen gas produced.
• What is the inverse square law?

  If we double the distance, then the number of bubbles per minute falls by factor 4. If we double the distance, the light intensity falls by 4 times. Because we need light for photosynthesis, that also causes the number of oxygen bubbles to fall by 4 times.
• Inverse square law?

  If you halve distance, light intensity 4 times greater

  
• What is respiration?

  Process of transferring energy from breakdown of glucose which happens in every cell in the body continuously
• What type of reaction is respiration?

  Exothermic- transfers energy to the environment
• 3 uses of energy transferred by respiration

  1. Chemical reactions to build larger molecules from smaller ones
  2. Allow muscles to contract to move
  3. Keep body temperature steady in colder surroundings for warmth
• Aerobic respiration?

  Occurs in mitochondria, releases alot of energy because the glucose molecule has been fully oxidised
• Aerboic Respiration formula?

  glucose+oxygen--> carbon dioxide + water (+energy)

  C6H12O6+O2--> CO2+H2O
• Anaerobic respiration in muscles?

  When shortage of oxygen, muscles respire anaerobically. Releases much less energy than aerobic because the oxidation of glucose is incomplete
• Anaerobic respiration in muscles formula?

  glucose--> lactic acid (+energy)
• Anaerobic respiration in plants and yeast?

  In yeast its called fermentation. Used to make alcoholic drinks, alcohol in drinks is ethanol and is produced by fermentation. Used to make bread, CO2 produced, creates bubbles in dough to rise
• Anaerobic respiration in plants and yeast formula?

  glucose--> ethanol+ carbon dioxide
• What is metabolism?

  Sum of all reactions that happen in a cell or the body
• What are the chemical reactions controlled by?

  Enezymes and many reactions are linked to form bigger reactions.

  Reactant +enzyme--> product+enzyme--> product
• • Lots small glucose molecules joined to form starch(storage in plant), glycogen(storage in animal), cellulose(plant cell wall)
  • Lipid molecules made from 1 molecule glycerol and 3 fatty acid
  • Glucose combined nitrate ions to make amino acids, then into proteins
• • Glucose broken down in respiration. Respiration transfers energy to power all reactions that makes molecules.
  • Excess protein broken to produce urea, then excreted in urine
• What happens when you exercise?

  • Muscles need energy from respiration to contract and you need more energy when doing exercise, so need more O2
  • Breathing rate and volume increases and heart rate increases to get O2 blood around body faster
  • You cant supply o2 to muscles fast enough so respire anaerbic
  • This is bad= lactic acid build up(painful), also causes muscle fatigue(tired), stop contracting efficiently