Flashcards
photosynthesis
Cards in this deck (24)
- 1what is the equation for phtotsynthesis?
- 2what energy is converted in photosynthesis?- Plants, algae and some types of bacteria uses light energy from sunlight into chemical energy.
- They can use the chemical energy to synthesise large organic molecules. - 3define Autotrophs- An organism which has the ability to form nutritional organic matter, from simple inorganic substances e.g CO2.
- 4define Heterotrophs- Organism that cannot manufacture its own food, so they must consume it.
- 5define Chemo-autrophs- An organism that obtains energy through chemical process. By oxidation of electron donating molecules.
- 6define Photo-autotrophs- Organism that use light as the energy source for autotrophic nutrition
- 7structure of a chloroplast- Small flattened, disc shaped organelles about 2-10um
- They have a double membrane (chloroplast envelope)
- Stroma (fluid filled matrix)
- Grana (containing thylakoids), also the intergranal lamellae which links two grana together - 8Explain the structure the Double Membrane- The outer membrane is more permeable
- The inner membrane is less permeable meaning tighter control of what goes in and out
- The space between the two membranes is called the Inter-membrane space. - 9What is the role of Grana- First stage of photosynthesis, the light-dependent stage takes place here
- Each stack of thylakoids is called = granum (up to 100 thylakoids)
- Grana (plural)
- Granum (singular) - 10what is the structure of Stroma and what happens here- It is a fluid filled matrix
- Light-independent stage occurs here
- It contains enzymes, sugars and organic acids
- Carbohydrates produced are stored as starch grains here - 11what are Photosynthetic Pigments and Photosystems- Photosystems are funnel shaped structures in the thylakoid membrane
-The photosystems contain Photosynthetic Pigments
- These are substances that absorb certain wavelengths of light and reflect others. - 12What are the two types of photosynthetic pigments?1) PRIMARY PIGMENTS
- ChlorophyllA
- They are reaction centres
2) ACCESSORY PIGMENTS
- ChlorophyllB
- Carotenoid (Xanthophyll and Carotenes)
- These make up light-harvesting systems, surrounding the reaction centres and transfer light energy to them to boost the availability of energy. - 13what colour does Chlorophyll-a appear? and what are their absorption peaks- Appear blue/green (so absorb red light)
- Situated at the centre of photosystems
- Different absorption peaks:
-> P680 found in PS2
-> P700 found in PS1
- Also absorbs some blue light, wavelength around 440nm - 14what colour does Chlorophyll-b appear? and what are their absorption peaks- Absorbs light; 400-500nm and 640nm
- Appears yellow/green - 15what light does Carotenoids photosynthetic pigment absorb- Absorbs blue light of wavelength 400-500nm
- Reflect yellow/orange light - 16what light does Xanthophyll photosynthetic pigment absorb- Absorb blue and green light of wavelengths 375-550nm
- They reflect yellow light - 17Characteristics of the Light-dependent reaction- Two types; cyclic and non-cyclic
- In the thylakoid membrane
- The light energy is absorbed by photosynthetic pigments in the photosystems and converted to chemical energy
- Light energy is used to add a phosphate group to ADP to form ATP and to reduce NADP
-ATP transfers energy and NADHP transfers hydrogen to the light-independent reaction.
- During this process H2O is oxidised to o2 - 18what happens in CYCLIC - photophosphorylation- Only produces ATP
- Involves only PS1
1) Light energy is absorbed by PS1
2) Pair of e- in the chlorophyll gain energy, becomes excited.
3) They escape from the chlorophyll and pass to an electron carrier system
4) e- loses its energy as it is passed along, this is used to make ATP
5) e- then return back to PS1
- Chloroplasts in guard cells only contain PS1
- They produce only ATP which actively brings potassium ions into the cells, lowering the water potential so that the water follows by osmosis
- Causing the guard cells to swell and opens the stoma - 19what happens in NON-CYCLIC photophosphorylation- Produce ATP and reduced NADP
- Involves both PS1 and PS2
1) Photon of light strikes PS2, in the primary pigment reaction centre
2) Light energy excites 2e- and caused them to escape out of the chlorophyll
3) The e- are captured by an electron carrier ( a protein with iron in centre, embedded in the thylakoid membrane)
4) Escaped e- do not come back therefore are replaced by new e- deprived from photolysis.
5) Iron ion (Fe3+) combines with e- and become reduced (Fe2+). Then donates e0 to the next electron carrier.
6) Energy is released as the e-'s are passed along the chain
7) This energy is used to pump protons (H+) across the thylakoid membrane into the thylakoid space
8) The e- are captured in PS1
9) As protons accumulate, a proton gradient forms across the membrane
10) Protons move down their conc gradient (chemiosmosis), into the stroma via an enzyme called ATP synthase. The energy from this movement combines ADP and inorganic phosphate to form ATP
11) Electrons and protons are accepted by NADP which becomes reduced. This is catalysed by NADP reductase - 20differences between the cyclic and non-cyclicNON CYCLIC
- Both photosystems involved
- Active reaction centre is P680
-ATP and NADPH produced
- Photolysis present
- E- does not comeback to PS2
CYCLIC
- Only PS1
- Active reaction centre is P700
- Produces ATP
- Photolysis not present
- E- comes back - 21Characteristics of the Light Independent stage- Also known as the Calvin cycle
- Also Carbon Dioxide Fixation because carbon is fixed into an organic molecule
- Takes place in the Stroma* - 22What happens in the Calvin Cycle1) CO2 enters the leaf through he stomata and diffuses into the storm of the chloroplast
2) Here it is combines with ribulose bisphosphate (RuBP), a 5-carbon compound. This gives an unstable 6-carbon compound, which breaks down into two molecules of a 3- carbon compound called glycerate 3-phosphate (GP)
3) Ribulose bisphosphate carboxylase (RuBisCO) catalyse the reaction between CO2 and ribulose bisphosphate
4) Now ATP (providing energy) and H+ ions (from reduced NADP) from the light independent stage is used to turn GP into trios phosphate (TP), another 30carbin compound
5) TP is then converted into many useful organic compounds
6) 6 cycles make 12TP, 2 TP (2x 3-carbon compound) is the product.
7) The 10TP is regenerated to form 6RuBP using the inorganic phosphate from ATP produced in the light dependent stage.
8) Six turns of the cycle requires 18 ATP (12 for converting GP-TP and 6 used to regenerate RuBP) and 12 reduced NADP. - 23why does the calvin cycle only run in the day- Products of the light dependent stage is continuously needed for the Calvin cycle
- During the LDS H+ are pumped from the stream into the thylakoid spaces, so the conc of free H+ falls in the storm rising the Ph to about 8.
- This ph is optimum for the enzyme RuBisCO
- RuBisCO is also activated by the presence of extra ATP in the stroma.
- In daylight, the conc of magnesium ions increases in the storm, these ions attach to the active site of RuBisCO acting as cofactors
- The ferredoxin that is reduced by e- from PS1 activates enzymes involved in the reactions of the Calvin Cycle. - 24Uses of TP- Some glucose is converted to sucrose/starch/cellulose
- Some Tp is used to synthesise amino acids,fatty acids and glycerol.
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- A-Level Biology (module 5.6 photosynthesis) Flashcards on photosynthesis, created by Hina Nagano on 08/10/2016.
- Created by
- Hina Nagano · Oct 2016
- Updated
- Apr 15, 2017
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