• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The effects of light intensity on the rate of photosynthesis.

Extracts from this document...


Biology Investigation The effects of light intensity on the rate of photosynthesis Introduction Photosynthesis involves an energy conversion in which light energy usually in the form of sunlight is converted into chemical energy stored in molecules of carbohydrate. The equation for photosynthesis is: The chlorophyll in the leaves of the plants absorbs the light energy. Some of this energy is used to produce ATP and some is used to split water molecules in the photolysis of water1. Light intensity as a limiting factor The amount of light available affects the amount of chlorophyll, which has excited electrons and therefore the amount of NADPH and ADP produced in the light-dependant stage. If there is a low level of light then insufficient NADPH and ATP will be produced to allow the reactions of the light independent stage to progress at their maximum rate. In this situation light is said to be the limiting factor for the process2. Also, not all wavelengths of light are equally effective at powering photosynthesis. However in my experiment I will be using a bulb, which will produce white light, as I know this, is an effective wavelength because the light from the sun is also white light3. Controlling the other limiting factors in photosynthesis If there is an insufficient supply of carbon dioxide in the reaction then there will not be enough available for fixation on the Calvin cycle, which means that the reaction cannot proceed at the maximum rate. ...read more.


Materials * Photosynthometers * Elodea- freshly cut at each end * Thermometer * Water * Clamp stand * Metre rule * Light bulb (100W) * Syringe * Sodium Hydrocarbonate Diagram of apparatus Method * Assemble the apparatus as shown in the diagram * Push in the plunger to the end of the syringe, making sure that there are no air bubbles in the tubing * Add 0.25g of Sodium Hydrocarbonate to the test tube with the elodea and stir it to dissolve * Measure the distance between the light bulb and the Elodea * Switch on the light bulb * Leave the Elodea to equilibrate * Then collect the oxygen given off for 5 minutes * Using the plunger in the syringe, carefully draw the bubbles up into the tube so that you can measure the length of the bubble. * Record this length * Repeat this procedure, each time moving the lamp away from the Elodea and measuring the distance * Throughout the experiment regularly checking the thermometer to make sure the temperature of the water remains constant. Results Length of bubble produced in mms Distance between light bulb and Elodea in cms Test 1 Test 2 Test 3 Average 0 70 34 76 60 10 12 15 32 19.66 20 6 10 23 13 30 3 6 12 7 40 2 3 5 3.33 50 1 1 2 1.33 After repeating my experiment 3 times I ...read more.


In my preliminary work I did a couple of tests using different amounts of sodium hydrocarbonate each time so that I knew that there would be an excess of carbon dioxide so that it would not be a limiting factor. I left the elodea to equilibrate before I began each test to let the plant adjust to the surroundings and allow it to perform photosynthesis at a constant rate I was also extremely vigilant with the amount of time I left the elodea to equilibrate, as I knew that this would have a rather dramatic effect on my results. I put a thermometer into the water surrounding the test tube so that I was able to keep a constant temperature. It was difficult to use exactly the same amount of Elodea each time so if I did this experiment again I would consider weighing the Elodea so that my results were more accurate. If I were to perform this experiment again then I would use a larger piece of elodea. This would mean that the amount of oxygen would have been larger and I could possibly decrease the light intensity to a greater extent and still be able to accurately measure the length of the bubble produced. Overall I think that my experiment worked out fairly well, as my results were similar to those, which I had expected. In my experiment I was able to prove that the rate of photosynthesis is affected by the light intensity. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Green Plants as Organisms essays

  1. Marked by a teacher

    Investigation to find out how light intensity effects the rate of photosynthesis

    4 star(s)

    But since only bubbles were counted, the volume of bubbles was not as important. But to volume of oxygen produced is important, since it was volume in terms of bubbles that were measured. As the rate of photosynthesis decreased due to a decrease in light intensity, the size of the bubbles produced also became smaller.

  2. Marked by a teacher

    Investigate the relationship between wavelength of light and the rate of photosynthesis using pondweed.

    3 star(s)

    After that the most bubbles produced were from the white light closely followed by red light, green, magenta and finally yellow. In the second run through, it did not show the same results, as white light produced the most bubbles, directly followed by blue, and then red light.

  1. Peer reviewed

    An Investigation into the Effects that Different Light Intensities have on the Speed of ...

    5 star(s)

    be with regard to the other results at their respective light intensities. This must have been a result of something slowing the woodlice down. I have offered explanations of these anomalous results in my evaluation. Evaluation: Explanation of results: First of all, I am going to consider the explanations for the experimental results that I obtained.

  2. Experiment to Investigate the Effect of Temperature on the Rate of Photosynthesis in Elodea.

    Instead of falling back into the photosystem and losing its energy as fluorescence, it is captured by an electron acceptor and passed to a chlorophyll a (P700) molecule via a chain of electron carriers. During this process enough energy is released to synthesise ATP from ADP and an inorganic phosphate group.

  1. Investigating the effect of Light Intensity on Elodea.

    * 1 Scalpel to cut the ends of the Elodea * 1 Stop clock to time the experiment * 1 white tile * 1 Spatula * 3x 1/4 Spatula of sodium hydrogen carbonate * 1m ruler Safety: * Keep the lamp and electricity plug + socket away from any water.

  2. Investigating the effect of temperature on the rate of photosynthesis

    This could have caused the enzymes to work at different speeds, causing the rate of photosynthesis to alter. Limitations: We could not fully control the light intensity, as even thought the room was blacked out to ensure no excess light contributed to the experiment, there were many other experiments occurring in the same room, therefore many other lamps.

  1. How temperature affects the rate of photosynthesis.

    As more products are formed by the reactions controlled by enzymes like photolysis and carbon fixation, the rate of photosynthesis is quicker. So higher the increase in temperature, higher the amount of kinetic energy gained by the enzyme and substrate molecules, higher the probability of successful collisions and therefore faster the rate of photosynthesis.

  2. This experiment involves using a photosynthometer to investigate how temperature affects the rate of ...

    photosynthesis is extremely slow due to the very slow diffusion of enzyme and substrate molecules through the ice lattice. Therefore I can make a firm prediction that for this particular investigation, the volume of oxygen produced will be rather small as oppose to being zero.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work