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21 Cards in this Set
- Front
- Back
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What was required practical 1? |
TLC of photosynthetic pigments of shade tolerant and intolerant plants |
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Give a brief overview of the method. |
Place the leaf in a mortar and pestle and grind with silver sand. Add a solvent a place a drop onto the base line of a TLC plate. Add a solvent and allow it to run up the plate, before it reaches the top, remove the plate |
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How do we calculate Rf values? |
Distance travelled by spot/ distance travelled by solvent |
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What results did we find? |
Shade tolerant plants have more photosynthetic pigments than shade intolerant as they encounter less light. So, more pigments mean they can absorb more wavelengths of light. |
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What was the second required practical? |
The effect of different wavelengths of light on the rate of photosynthesis |
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What chemical do we use in this practical and why? |
DCPIP as it acts like NADP and accepts an electron to become reduced. It changes colour from blue to colourless. |
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Give a brief overview of the method. 2 |
Extract some of the leaf solution into a capillary tube and place on a white tile. Add DCPIP to the leaf extract until it goes from green to blue-green. Then wrap the container in foil. We then set up a lamp and made up a new capillary tube and placed it next to the colour standard. We put a purple filter over them, switched the light on and recorded how long it took for the colours to become the same. We repeated for different coloured filters. |
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How do we work out rate of reduction? |
1000 / t in seconds |
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What precautions did we take? |
We put foil around the beaker to stop light reaching it, slowing photosynthesis. We kept the light 20cm away from the tubes to ensure light intensity was constant. |
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What other control should we have used? |
We should've made a capillary tube of DCPIP alone,to show it doesn't change colour by itself |
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Why did it not matter that CO2 concentration wasn't controlled? |
It affects the LIR not the LDR |
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What was the third required practical we did? |
Investigating the effect of light intensity on the rate of photosynthesis and identifying the compensation point. |
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How do we make the algae balls? |
Place sodium alginate into a clean test tube with concentrated algal suspension and mix. Use a syringe to drop the suspension into calcium chloride and leave to form solid algae balls. Extract with a tea strainer and rinse with distilled water. |
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Give a brief overview of the method. 3 |
Place the McCartney bottles filled with indicator and algae balls in a line drawn on graph paper. Set up the lamp on its side facing the bottles. Switch it on and measure the light intensity at each point. Place the caps on the bottles, leave, transfer the solutions into cuvettes and measure absorbance. |
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What filter is used in the colorimeter? |
Green |
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What indicator solution do we use and why? |
Hydrogen carbonate indicator solution. It's yellow at a low pH, then goes to red and then goes to purple at a high pH. |
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What happened as light intensity increased? |
Absorbance increased as the rate of photosynthesis increased, so there was less CO2 in the solution and it became more purple |
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What controls were used? |
Bottles with no algae balls at all light intensities. A bottle in the dark |
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What was required practical 4? |
The effect of different substrates on the rate of yeast respiration |
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Give a brief overview of the method.4 |
We filled a beaker with warm water and placed an upside down Durham tube with yeast and glucose in a test tube. We measured the length of the air bubble at the top of the Durham tube. We did this for each sugar. We recorded the height of the bubble at 5,10,15 and 20 minutes. We then subtracted the initial height from readings. |
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What control did we use? |
A Durham tube containing only yeast and no substrate. Or just substrate. |
