Objectives
2.Mix 5cm3 of algal culture with 5cm3 of 3% sodium alginate solution in a very small beaker with a cocktail stick
3.Clamp a syringe barrel above a beaker of calcium chloride solution making sure the tip of the syringe is well above the solution in the beaker
4.Pour the alginate mixture through the syringe so it drips through and forms beads in the beaker. Swirl the beaker gently as the drops fall. If the solution is too thick dilute with a little more algal suspension. If it is running through too quickly, mix in more alginate
5.Allow the beads to harden for a few minutes before straining them out of the beaker through a tea strainer
6.Rinse the beads in distilled water which will allow the algae to stay alive
2.Add an equal number of algal balls to each container; 20
3.Added 5cm3 of indicator to each container
4.Replace the lid
5.Surround each vial with a different coloured light filters and have one without a filter
6.After 3 days note the colours of the vials and compare this to the indicator spectrum
7.Record results in a suitable table
Results
- Learn how to trap algae in alginate beads
- Use algae in beads to investigate how light wavelength affects photosynthesis
- Evaluate this method for investigating photosynthesis and plan your own investigations
- Scissors to cut the light filters are sharp
- 3% sodium alginate solution
- Algal culture
- Hydrogen carbonate indicator solution
- 50cm3 syringe
- Clamp
- Different colour light filters
- Making your algal beads
2.Mix 5cm3 of algal culture with 5cm3 of 3% sodium alginate solution in a very small beaker with a cocktail stick
3.Clamp a syringe barrel above a beaker of calcium chloride solution making sure the tip of the syringe is well above the solution in the beaker
4.Pour the alginate mixture through the syringe so it drips through and forms beads in the beaker. Swirl the beaker gently as the drops fall. If the solution is too thick dilute with a little more algal suspension. If it is running through too quickly, mix in more alginate
5.Allow the beads to harden for a few minutes before straining them out of the beaker through a tea strainer
6.Rinse the beads in distilled water which will allow the algae to stay alive
- Investigating photosynthesis
2.Add an equal number of algal balls to each container; 20
3.Added 5cm3 of indicator to each container
4.Replace the lid
5.Surround each vial with a different coloured light filters and have one without a filter
6.After 3 days note the colours of the vials and compare this to the indicator spectrum
7.Record results in a suitable table
Results
Analysis of results
Light filters wrapped around the bottles can be used to filter different wavelengths of light. “If photosynthesis can proceed at a rate that exceeds respiration, the indicator solution will change towards the more purple/ alkaline”. Therefore, if the algae cannot photosynthesis at a rate exceeding respiration the solution will be more acidic / yellow. The reason that the rate of photosynthesis changes depending on the wave length of light is because within algal cells are chloroplast which contain different photosynthetic pigments which all operate at different wavelengths of light. At certain wave lengths of light, more pigment may be used and in different quantities. This can be shown in an action spectrum which shows the absorbance of light at different wave lengths of light. The spectrum below is for a plant[1], not specifically algae which would have a different spectrum to be adapted to living in water in which water has to penetrate. When there is no filter of different wave lengths of light the algae’s photosynthesis should be unaffected so we would expect this to be the highest pH, which it is. If the filter is green this means that the only colour allowed into the bottle which is wavelength 475-590nm. As the pH is around 7.7 this means that the algae was photosynthesising at a reduced rate than respiration. This is because the area in of the action spectrum that the chlorophyll is being utilised is relatively low so therefore the solution becomes more acidic. This is the same for each wavelength
[1] http://photobiology.info/Gorton.html
Light filters wrapped around the bottles can be used to filter different wavelengths of light. “If photosynthesis can proceed at a rate that exceeds respiration, the indicator solution will change towards the more purple/ alkaline”. Therefore, if the algae cannot photosynthesis at a rate exceeding respiration the solution will be more acidic / yellow. The reason that the rate of photosynthesis changes depending on the wave length of light is because within algal cells are chloroplast which contain different photosynthetic pigments which all operate at different wavelengths of light. At certain wave lengths of light, more pigment may be used and in different quantities. This can be shown in an action spectrum which shows the absorbance of light at different wave lengths of light. The spectrum below is for a plant[1], not specifically algae which would have a different spectrum to be adapted to living in water in which water has to penetrate. When there is no filter of different wave lengths of light the algae’s photosynthesis should be unaffected so we would expect this to be the highest pH, which it is. If the filter is green this means that the only colour allowed into the bottle which is wavelength 475-590nm. As the pH is around 7.7 this means that the algae was photosynthesising at a reduced rate than respiration. This is because the area in of the action spectrum that the chlorophyll is being utilised is relatively low so therefore the solution becomes more acidic. This is the same for each wavelength
[1] http://photobiology.info/Gorton.html
Questions
1.What tips would you have for someone making algal beads like this?
I believe my results are valid, the light filters were all put onto the vials in the same way and all vials received nearly the exact same amount of light over the time period. I think I could make my results more reliable by adding more light filters and see if the wavelength of light changes the results like expected
1.What tips would you have for someone making algal beads like this?
- Use a syringe to add the algae into the solution so that the beads of algae are all uniform size and thickness
I believe my results are valid, the light filters were all put onto the vials in the same way and all vials received nearly the exact same amount of light over the time period. I think I could make my results more reliable by adding more light filters and see if the wavelength of light changes the results like expected