CB6 - Plant & functions (Photosynthesis)

• Whats the word equation for photosynthesis?

  Carbon dioxide + water --> glucose + oxygen
• Where does photosynthesis take place?

  In the chloroplasts of the plant cell:

  They use energy from light to transform carbon dioxide and water into glucose and oxygen.
• Why is photosynthesis important?

  It provides oxygen so we can breathe
• What substance allows for light to be absorbed during photosynthesis?

  Chlorophyll (green substance found in chloroplasts)
• In which part of the plant does photosynthesis mostly take place?

  On the leaf
• Is photosynthesis endothermic or exothermic?

  Endothermic - light energy is taken in from the environment
• Why would the products of photosynthesis have more energy than the reactants?

  Because photosynthesis is an endothermic so more energy is being absorbed than released.
• What is biomass?

  The mass of living material in an organism
• What polymer is formed when glucose molecules link together?

  Starch
• 5 ways that the plant can use the glucose they produce

  ~ Cellular respiration - Break down the glucose to release the energy.

  ~ Make cellulose - which is used to create strong cell walls.

  ~ Make starch - which is used to store glucose for later use.

  ~ Make amino acids - which is used to make proteins.

  ~ Make lipids - these store energy as fats and oils for later use.
• What type of sugar molecule is transported around the plant?

  Sucrose - made when glucose forms it
• What is sucrose used for?

  ~ Storage - for excess sugars and carbs (like in Potatoes) and stored in the from of sucrose

  ~ Providing energy for the plant as it releases energy through respiration
• What is a 'limiting factor'?

  Something that stops photosynthesis happening faster or stops it completely
• What are 3 environmental factors that affect the rate of photosynthesis

  ~ Temperature

  ~ Light Intensity

  ~ CO2 Concentration
• Why is photosynthesis slower as you go higher above sea level?

  ~ Theres less CO2 in their air and CO2 is a substrate in photosynthesis hence distrupting photosynthesis

  ~ Theres gonna be increased exposure to UV radiation damaging chloroplasts and other cells
• Describe and explain how the rate of photosynthesis varies with temperature

  ~ In the graph the rate initially increases with the temperature as particles have more energy and are moving faster, hence they react more frequently.

  ~ The highest rate occurs at the optimum temp for the enzymes.

  ~ At higher temperatures the rate starts to decrease as bonds holding the enzymes together start to break & the enzyme denures, changing shape so they're no longer complementary w/ the substrates.

  ~ The rate falls to zero as enzymes denature.

  
• What could be the limiting factors in a light intensity graph?

  And some other details abt light intensity

  ~ In this graph the rate initially increases then levels off.

  ~ The limiting facts would be less CO2 and less temp.

  ~ The more light, the more stomata will be open, meaning more CO2 going in hence more photosynthesis.

  ~ But the distance from the light source is directly proportional to the light intensity.

  
• What could be the limiting factors in a CO2 concentration graph?

  ~ In this graph the rate initially increases then levels off.

  ~ The limiting factors would be less light and less temp.

  
• Why do farmers use greenhouses?

  ~ Greenhouses help trap the heat energy from the sun so the temperature doesnt become limiting.

  ~ They keep pests and animals out that can potentially damage the plant.

  ~ They make it easier to control the conditions like CO2, levels , water, temp and fertilisers so theres no limiting factors.
• What are paraffin heaters and why are they used in greenhouses?

  ~ Paraffin heaters burn a fossil fuel called parrafin.

  ~ This produces carbon dioxide and heat energy, both of which help plants grow.
• What's the method for investigating light intensity using pondweed? (core practical)

  1. Add pondweed to hydrogen carbonate solution (contains the CO2 the plant needs).

  2. Place the light at a specific distance.

  3. Leave the pondweed to photosynthesise for a set amount of time.

  4. Measure oxygen released by counting bubbles or using a gas syringe (more accurate).

  5. Repeat with light source at diffent distances.

  
  

  ~ The more oxygen, the more photosynthesis

  This can be changed to test another variable
• Whats the method of measuring light intensity using algae balls? (core practical)

  1. Put a set number of algae balls and volume of hydrogen carbonate indicator in each tube.

  2. Measure the initial pH (by comparing the solution with a chart or with buffered solutions).

  3. The bottles are kept equal distances along 1m rule.

  4. Light switched on for set amt. of time.

  5. Measure the final pH and calculate the change in pH.

  
  

  ~ C02 makes the solution acidic, so the more the photosynthesis, the more CO2 used hence higher ph

  ~ Higher ph = more photosynthesis

  This can be changed to test another variable
• What saftey precautions would you have to take when making algae balls?


  ~ Wear gloves

  ~ Wear goggles

  ~ Ensure the area is ventilated