photosynthesis Flashcards
ATP
-Adenosine triphosphate
-nitrogenous organic base
-ribose sugar
-3 phosphate groups
-used as an energy source
Use of ATP
-provides energy ( active transport)
-phosphorylation ( binds to enzymes/substrates and lowers the Ea or alters the 3 structure
why is ATP useful
-releases energy in small manageable amounts
-broken down in one step
-immediate energy compound
-phosphorylates
-lowers activation energy
-reformed
forming ATP
-ADP and inorganic phosphate
-requires energy to add a phosphate to ADP-forms ATP with a high energy bond
-condensation reaction
breaking ATP
-into ADP and inorganic phosphate
-bond between 2nd and 3rd phosphate breaks
-releasing small manageable amounts of usable energy
-hydrolysis reaction which requires 1 molecule of water
Give two ways the hydrolysis of ATP is used in cells
-muscle contraction
-active transport
NADP
- Nicotinamide Adenine Dinucleotide Phosphate
-acts as a hydrogen acceptor
-reduced to form NADPH
-NADPH is a reducing agent
-it can donate H+ to other molecules in REDOX reaction
-NADPH becomes oxidised (to NADP) and the other molecule that accepts the H+ is reduced
Photosynthesis equation
6CO2 + 6H20 —> C6H12O6 + 6O2
chloroplasts
site of photosynthesis
thylakoids
-contains chlorophyll in the membrane
-Large SA
-Has light dependent reactions
Granum
a stack of thylakoids
stroma
-enzyme controlled reactions take place
-light independent reactions
starch grain
- alpha glucose monomers
-linked by glycosidic bonds
70s ribosomes
-site of protein synthesis
circular DNA characteristic
-shorter DNA
-not associated with histones
-has genes that code for proteins involved with photosynthesis
membranes
-inner membrane
-outer membrane
Light dependent reactions
-in the Granum
-light + H2O —> O2 + NADPH +ATP
Light independent reactions
-in the Stroma
-CO2 + NADPH + ATP —-> Glucose
Light dependent reactions ( 6 marks)
-chlorophyll absorbs light energy via (photoionisation)
-electrons become excited so chlorophyll is oxidised
-electrons then move across the electron transport chain
-energy released by electrons produces a proton gradient
-H+ ions then diffuse through the ATP synthase via (photophosphorylation)
-provides energy to join ADP + Pi to form ATP
-electrons that left chlorophyll are replaced by electrons from water molecules via (photolysis) so chlorophyll is reduced
- H+ and an associated electron are used to reduce a Hydrogen carrier NADP to form NADPH
site of photolysis
thylakoid space
proton electrochemical gradient
- high conc. of H+ ions in thylakoid space than on the other side of the membrane
-H+ ions diffuse from high to low conc. to try to reach equilibrium
-can only move through ATP synthase
herbicide
-Reduced transfer of protons across thylakoid membrane
-Reduced proton gradient across thylakoid membrane
-less ATP produced
-less NADPH produced
-light-independent reaction slows/stops
Fluorescence
- ETC not available for excited electron
-releases energy as light
suggest why LID reaction is not the only source of ATP
- plants don’t photosynthesise in the dark
-not all parts can photosynthesise (roots)
-plants require more ATP then what is produced in the LDR
-ATP used in active transport
Light Independent reaction 3 phases:
- Carbon fixation
- Reduction
- Regeneration
Light independent reaction ( 5 marks )
- CO2 fixes with RuBP
produces 2x glycerate-3-phosphate
-GP reduced to triose phosphate
-using NADPH
-using energy from ATP hydrolysis
-TP converted to glucose/amino acid
-most TP used to regenerate RuBP
RP7: Chromatography method
-draw a straight line in pencil 1cm above bottom of filter paper
-place leaf in mortar, add acetone + use pestle to grind up leaf + release the pigments
-use capillary tube to extract some of pigment + blot it on centre of pencil line
-suspend paper in solvent and ENSURE the liquid isn’t above the pencil line
-leave paper until the solvent has run up paper to near the top
-remove paper from solvent + draw a pencil line marking solvent front
-calculate Rf value for each spot
RP7: why use a pencil to mark the line?
- ink and pigments would mix
RP7: Rf value equation
Rf= distance moved by pigment/ distance moved by solvent front
factors affecting photosynthesis
- temp
- light intensity
- co2 conc.
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours.
Use your knowledge of photosynthesis to describe these changes and explain why they occur. [5]
-High concentration of carbon dioxide linked with night
-No photosynthesis in dark as light is required for photosynthesis
-In dark plants respire instead
-Plants use more carbon dioxide than they produce
-Decrease in carbon dioxide concentration with height
-At ground level less light
(e.g. roots do not photosynthesise)
