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

Photosynthesis Lab

Extracts from this document...


Wednesday 25th of Mach 2009 IB Photosynthesis Experiment: Hill Reaction Aim of the Experiment: To analyse the effects of light intensity on photosynthesis via the Hill reaction. Research Question: How does light intensity affect the rate of photosynthesis more precisely the rate of reaction in photosystem II, at the primary acceptor location? Hypothesis: In the light dependant reactions, an artificial electron acceptor, DCPIP can be substituted for NADP it is very similar to this molecule but changes colour when it is reduced; it changes from blue to colourless. This is because DCPIP is a redox dye. As DCPIP becomes colourless light transmittance is therefore increased and one can use a colorimeter to measure the light acceptance. This means that it is the rate of electron flow in photosynthesis that is being measured. It is also important to note that DCPIP interrupts the passage of electrons from photosystem II to photosystem I, explaining why only photosystem II activity can and is measured. For this experiment the variables are the following: Independent variable: Light intensity - Produced from a lamp at various distances. Dependant variable: Transparency- Light absorbance of the solutions Controlled variable: Ambient Light - The shutters were closed to stop sunlight from entering the room in which the lab took place. ...read more.


A disagreement is noticed in the last set of values. Graph 2. This graph shows the average values plotted and their respective error bar. A trend is easily noticed as the values increase in a logarithmic way, steadily approaching a certain optimum. However the last value (44.5 Wm-2) does not correspond to anything expected and is an admitted error possibly caused by another limiting value of photosynthesis that has changed, such as temperature. Conclusion An undetermined but possibly non-linear regression relation was found; possibly a logarithmic one as Blackman and Wilson's "Physiological and ecological studies in the analysis of plant environment" heavily suggests this as it is stated that "the net assimilation rate during the season of active growth is linearly related to the logarithm of the light intensity". However a clear conclusion that has to be made is that light is indeed a limiting and essential factor to the rate of photosynthesis in photosystem II, as it is light that provides photons and excites electrons as soon as it touches the pigment molecule. In isolated chloroplasts, light is required as the name of the observed reaction states, light dependant reaction. In addition, since DCPIP stopped electrons from passing from photosystem II to I, the primary products of the light dependant reactions, ATP and NADPH2, could not have been required and the Calvin cycle had no resources available to take place. ...read more.


This could have easily been fixed by placing the cuvettes in an alternating fashion, describe in a diagram besides. The experiment's quality was also deteriorated by the light pollution emitted by surrounding experiments in the room. The simple solution is simply to do each experiment one at a time. DCPIP being a blue compound itself when oxidized obscured the light intended for the chloroplasts to react causing the rate of reaction to happen at an increasing rate while the DCPIP reduced, becoming colourless. Another factor that would have increased the quality of the results would have been to use a lux meter to measure the illuminance at various distances and not have to really on the relationship, which is not the most precise way of measuring light intensity. Finally more distances should have been tested, as we have no data for 15 to 45 Wm-2. Distances such as 16, 17 ,20 ,22, 25, 27 would have been extremely useful for two reasons. Firstly because we would have data for the large range of light intensity blank and we would have had 12 different measures allowing a proper statistical test to be used. In this case a non-linear regression test would have been the most suited for testing the relationship. ?? ?? ?? ?? | International School of Paris ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Biology 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 International Baccalaureate Biology essays

  1. Biology Lab Report-Osmosis

    then it becomes iso-osmotic, and eventually (at 0.3M NaCl), the solution becomes hyper-osmotic. Thus, the cells of the potato chips immersed in the solutions of concentrations 0.3M and 0.4M NaCl lose water to their surroundings and become plasmolysed. Conclusion: From the tables, observations and the analysis, these are the conclusions

  2. Plant Tropism Lab

    45 52 T-1 - - - 26 6 - T-2 - - - 15 22 - T-3 - - - - 131 - T-4 - - - 67 113 - T-5 - - - 102 19 - K-1 - - 0 40 25 -50 K-2 - - -30 35 20

  1. Lion King-The Ecological study

    Firstly, there must be water, sun, nutritional soil for grass to grow. After a while, insects, such as grasshopper, begin to go over the grass land and begin to consume the grass. Not just the insects but herbivores (antelope) also came over and eat the grass.

  2. Experiment Colours of Light (Wavelength) absorbed by green plant

    Hence, more wavelengths is absorbed rather than reflected at these points of wavelengths. However, at the bottom of the graph, it can be deduce that the mustard sample does not really absorb much wavelengths at point 540 nm with an absorption percentage of 1.30%.

  1. Bio lab - Oxygen Consumption in germinating and non-germinating seeds

    value from germinating and non-germinating seeds from the room temperature and the ice water were calculated and displayed in the chart. It was calculated at 5 minute interval. Processed Graph 1: The graph of average oxygen consumption in room temperature and in ice water for both germinating and non-germinating seeds is shown.

  2. Factors Affecting the Rate of Photosynthesis Lab

    Place the elodea in the solution so that the stem points upward towards the opening of the beaker 4. Put a glass funnel into the beaker (wide end down, tube pointing upward) so that it helps to keep the elodea at the bottom of the solution and angles the stem upward 5.

  1. Identification of Carbohydrates ,Lipids,and Proteins lab

    humans ? should drink more of it for a balanced healthy diet. This experiment did not run as smoothly as I thought it would. Certain tests had problems that may have resulted in inaccuracy of results or frustration during experimentation.

  2. Plan for an experiment - How does temperature affect the rate of photosynthesis?

    all the temperatures and therefore won?t also affect the experiment and the results. Lux Clamp and Stand 1 To hold the capillary tube and gas syringe. - Capillary Tube 1 To hold the oxygen bubbles produced so they can be measured.

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