Lesson 4: Photosynthesis Flashcards
What type of reaction is photosynthesis and why?
- Endothermic reaction
- Light energy is transferred from environment to the chloroplasts.
Give ths symbol equation for photosynthesis.
6CO₂+ 6H₂O —> C₆H₁₂O₆+ 6O₂
_ light (on top of arrow!)
What effect does increasing light intesnity have on the rate of photosynthesis?
- More light energy, means the reaction of photosynthesis can take place quicker.
to a limit
What effect does increasing concentration of CO₂ have on the rate of photosynthesis?
- Increased rate of photosynthesis.
to a limit
What effect does increasing temperature have on the rate of photosynthesis?
- KE of reactants increases - increased collisions - increased rate of reaction.
- If too low: rate decreases as enzymes and reactants have decreased kinetic energy so less collisions.
- If too high, enzymes denature
How is the glucose produced by photosynthesis used by the plant?
5 ways
- Respiration
- converted into insoluble starch for storage.
- Used to produce fat / oil for storage.
- Used to produce cellulose, which strengthens the cell wall.
- Used to produce amino acid for protein synthesis.
What else do plants use to form amino acids other than glucose?
- To produce proteins, plants also use nitrate ions that are absorbed from
the soil.
What are the steps to the practical: Investigating light intensity on the rate of photosynthesis?
1.) Place boiling tube 10cm away from LED light - source.
2.) Fill the boiling tube with sodium hydrogen carbonate solution.
3.) Place a piece of pomdweed in the boiling tube with the cut end at the top.
4.) Leave pondweed for 5 mins to allow it to acclimatise to conditions in boiling tube.
5.) After you see bubbles in boiling tube (Oxygen), start a stopwatch and count number of bubbles produced in one minute.
6.) Repeat this two more times and calculate the mean number of bubbles produced per minute.
7.) Repeat experiment at 20, 30 and 40cm from LED.
Why do we use an LED light in the required practical?
- LED lights don’t release too much heat.
- Too much heat will effect the temperature of the experiment (should be a control!!)
If you don’t have an LED and need to use a normal bulb, what should you do to make sure the temperature of the boiling tube doesn’t increase?
- Place beaker of water between boiling tube and bulb.
- Beaker of water will absorb the energy released by the bulb, rather than the boiling tube.
Why do we fill the boiling tube with sodium hydrogen carbonate solution?
- Sodium hydrogen carbonate solution releases carbon dioxide.
- This is needed for any photosynthesis to occur in the experiment.
What are the 2 main problems in the method of the required practical?
1.) Number of bubbles can be too fast to count accurately.
2.) Bubbles aren’t always the same size: some contain more oxygen than others.
How can we solve the 2 problems in the method of the required practical?
- Measure volume of oxygen produced instead of counting bubbles.
- Place pondweed under a funnel, catch bubbles in measuring cyclinder filled with water.
- See how much the water is pushed down –> that’s the volume of oxygen produced.
What is the inverse square law in the required practical?
- As you double the distance of the plant from the light- source, the number of bubbles falls by 4 times.
What is a “limiting factor?”
- A limiting factor is an environmental condition that decreases the rate of photosynthesis when in short supply.
