3.2 Photosynthesis uses light energy to synthesise organic molecules Flashcards
Where is chlorophyll found?
In thylakoid membranes of the chloroplast
What type of feeding is photosynthesis?
Autotrophic nutrition
4 photosynthetic pigments
Chlorophyll A and B
Carotenes
Xanthophyll
What light is absorbed by chlorophyll?
red and blue-violet
What light is absorbed by carotenoids?
blue violet
Why do plants appear green?
As none of the pigments absorb green light and so it is reflected
Why is it beneficial to have more than 1 pigment type?
To absorb a wider range of light waves, allowing more efficient photosynthesis
Why is it beneficial to have more than 1 pigment type?
To absorb a wider range of light waves, allowing more efficient photosynthesis
What is shown by the absorption spectra?
How much light is absorbed at different wavelengths
What is shown by the action spectra?
The rate of photosynthesis at different wavelengths
What are the main functions of the light dependent stage?
- split water molecules by photolysis releasing H+
- ATP synthesis supplying energy for carbohydrate synthesis
What photosystems are used in non cyclic photophosphorylation?
PS I and PS II
What photosystems are used in cyclic photophosphorylation?
PS I
How do electrons move in non cyclic photophosphorylation?
rise up energy levels and move down electron transport chin to next photosystem
Do not return to original photosystem
How do electrons move in cyclic photophosphorylation?
Electrons rise up energy levels and then return to original photosystem
What shape are chloroplasts?
lens
What shape are mitochondria?
Rod
Organelles of chloroplast (3)
Grana, stroma, thylakoid
Organelles of mitochondria (2)
Cristae, inner matrix
What is chemiosmotic theory?
ATP synthesis takes place by a flow of protons across membranes, down a conc gradient through the enzyme ATP synthetase in stalked particles.
How is light energy absorbed by a plant?
Though Photosynthetic pigments in photosystems
What happens to the absorbed light energy?
it is funneled to the reaction centre where it excited electrons
What happens to the excited electrons at PS II?
They rise up to an electron receiver where they are then passed down the electron transport chain to PS I
What happens as the electrons move down the electron transport chain?
Protons are actively transported out if the thylakoid membrane creating a proton gradient
What happens to the protons after they leave the membrane?
They move from an area of high to low concentration passing through a stalked particle to re-enter the membrane, creating energy
What uses the energy created by the proton flow?
It catalyses the joining of P to ADP forming ATP via ATP synthetase
Where do the electrons and protons come from?
The photolysis of water to form 2 protons and 2 electrons- oxygen released as a bi-product
What cycle occurs in the light independent reaction?
Calvin cycle
What is the first stage of the calvin cycle?
RuBP is fixed with carbon dioxide in a reaction
catalysed by RUBISCO.
What is the second stage of the calivn cycle?
RuBP is converted into two glycerate 3-phosphate
What is the third stage of the calvin cycle?
2 ATP are used to convert glycerate-3-phosphate to glycerate diphosphate
What is the fourth stage of the Calvin cycle?
Reduced NADP is oxidised as GD goes to triose phosphate
What is the 5th stage of the Calvin cycle?
ATP is released and most TP regenerates to RUBP
Some forms glucose
What are the limiting factors of photosynthesis?
Temperature
Light intensity
CO2 Concentration
How does temperature affect photosynthesis?
Enzyme catalysed reaction, therefore has optimum and can denature
How does Light Intensity affect photosynthesis?
Limited by number of photosystems
high Light intensity bleaches photosystems
How does CO2 concentration affect photosynthesis?
Increases the rate of CO2 incorporation in the Calvin cycle and is only limited by other factors
Where does the light independent reaction occur?
Stroma
How does Calvins lollipop experiment work?
- Algae is grown under light
- Radioactive carbon is injected
- At intervals, photosynthesising algae are
- Dropped into hot methanol, stopping any reactions
- Algae are separated in two way chromatography
