2.9 Photosynthesis Flashcards
What is Photosynthesis? SL
It is the production of carbon compounds in cells using light energy. It is an example of energy conversion as it converts light energy into chemical energy.
How do you separate photosynthetic pigments?
By chromatography. Because different photosynthetic pigments absorb different wavelengths of light they look different colours to us. These can be separated.
This is best done with TLC, thin layer chromatography paper.
1) Extract pigments from the leaf by tearing it into small pieces, grinding and adding propanone (acetone).
2) Filter out the liquid from the solids and then hairdry off the propanone so you just have the pigments.
3) When it has all been evaporated then you can add some more propanone and then put the solution on to the bottom of the TLC strip.
4) This dot need to be very very very dark, so keep putting the pigment solution on, drying it with a hairdryer and putting another dot on to when it is dry.
5) Then put the paper into the solvent, THE SOLVENT MUST NOT BE HIGHER THAN THE BOTTOM OF THE PIGMENT AND MUST NOT TOUCH IT.
6) Leave it alone and let the solvent run up. Then measure the distance of the solvent and each of the spots and measure the retention factor.
Which light is absorbed best by chlorophyll?
Red and blue light are absorbed the best and green light is absorbed the worst it is reflected more than any other colour. This is why the leaves appear green to us because all of the light is absorbed except green which is reflected.
Draw the absorption and action spectra of chlorophyll?
A line graph with percentage absorption (absorption spectra) or percentage photosynthesis (action spectra) on the y axis and wavelength ranging from 400 to 800 on the x axis.
The absorption one should have a few lines on it and rise over 400 - 550 and then drop over 550-700 and then rise again, as there is hardly any absorption of green light.
The action spectrum should be the same but be higher up so a higher percentage and just be one line.
How is oxygen produced in photosynthesis?
From the photolysis of water. H2O + H+ + 2e- + O.
What are the effects of photosynthesis on earth millions of years ago?
It caused a rise in the oxygen concentration, which reduced the greenhouse gases and then when the first prokaryotes started photosynthesising the first glaciation took place 2,200 million years ago.
2,400 to 2,200 million years ago increase in the oxygen concentration of the sea caused the oxidation of dissolved iron in the rock causing it to precipitate on to the seabed. A distinctive rock formation was produced called the banded iron formation, with layers of iron oxide alternating with other minerals. The reasons this happened are not well understood but they are the most important iron ores SO THANKS PHOTOSYNTHESIS.
What are the limiting factors of photosynthesis?
- Temperature
- Light
- Carbon dioxide concentration
