Photosynthesis - Finished Flashcards
What is Photosynthesis?
The process (occuring in plants and some other organisms) by which carbohydrates are synthesis from carbon dioxide using light energy as an energy source.
What is the equation for photosynthesis?
6CO2 + 6H2O -> C6H12O6 + 6O2
Where is the main site of photosynthesis?
The chloroplasts in the Palisade Mesophyll cells/tissue
What are the 4 main photosynthetic pigments?
- Chlorophyll A
- Chlorophyll B
- Carotene
- Xanthophyll
Where are the photosynthetic pigments located?
in the Thylakoid membranes
What is the fuction of the photosynthetic pigments?
To absorb light energy
What was Engelmann’s experiment?
He reflected a rainbow of light onto a strip of algae and saw that the motile bacteria that fed off the algae clustered towards the algae under the red and blue light. This shows that the red and blue light wavelengths resulted in increased photosynthesis whiched produced more oxygen that attracted the bacteria which need oxygen for respiration.
What is an absorbtion spectrum?
A graph that shows how much light is absorbed at different wavelengths.
What is an action spectrum?
A graph that shows the rate of photosynthesis at different wavelengths.
What is the relationship between the action and absorbtion spectrum?
The graphs have a similar shape. This suggests that it is the absorbance of light that allows photosynthesis to occur.
What is the advantage to a plant of having more than 1 photosynthetic pigments?
Each pigment absorbs light from a limited part of the spectrum .
Additional pigments allow a range of different wavelengths of light to be absorbed.
This enables an increased rate of photosynthesis so more carbohydrates are made.
What is a photosystem made up of?
- Antenna Complex - A cluster of photosynthetic pigments in the thylakoid membrane.
- Reaction centre - where the light is funnelled to.
How many photosystems are there?
Photosystem 2 = Also called P680 as its chlorophyll A molecule has an absorption peak at 680nm
Photosystem 1 = Also called P700 as its chlorophyll A molecule has an absorption peak at 700nm
What are Photosystems for?
For Light Harvesting and Donating Protons
Where would you find a photosystem?
In the light dependant stage of photosynthesis
Where does the light dependent stage happen in a plant?
Thylakoids
What is the light dependant stage also known as?
The Z scheme
What is the light dependant stage made up of?
2 photosystems and an electron transport chain.
What happens in the light dependant stage of photosynthesis?
- When light energy reaches the reaction centre of the photosystem 2. Chlorophyll A emits 2 electrons and leaves the chlorophyll oxidised.
- These electrons are raised up to a higher energy level and are picked up by electron accepters
- The electrons pass along a chain of electron carriers and proton pumps resulting in the generation of ATP from ADP (By a process called photophosphorylation)
What happens to the electrons that are emmitted from photosystem 1?
They either re-enter the electron transport chain to be used in cyclic photoposphorylation
or they are used with 2H+ to reduce NADP
How does the Chlorophyll A in photosystem 2 replenish its electron number?
a molecule of H2O breaks down by photolysis and donates 2e- to photosystem 2 and a 2H+ to reduce NADP
What are the 4 main things the light dependant stage consists of?
- Electron transfer through the z scheme
- reduction of NADP
- photolysis of water
- Synthesis of ATP by photophosphorylation (cyclic/non-cyclic)
THESE PROCESSES ARE INTERLINKED
Where is the source of electrons for cyclic and non-cyclic photophosphorylation?
Cyclic = Derived from photosystem 1 - pass along the first ETC and return to PS1
Non Cyclic = Derived from water. They pass through the z scheme untill they end up in reduced NADP
what photosystems are used in cyclic and non cyclic ?
Non Cyclic: PSI PSII
Cyclic: PSI