5.6 photosynthesis Flashcards
autotroph
produce their own energy
general FORMULA equation for photosynthesis
6CO2 + 6H2O -> C6H12O6 + 6O2
compensation point
- photosynthesis and respiration occur at same rate
how many membranes does a chloroplast have?
3
outer
inner
thylakoid
large circle in chlorplast
starch grain
where does LDR take place
thylakoid
where does LIR take place
stroma
adaptatiosn of grana
- large SA so many photosystems so max absorption of light
- more membrane space for ETC and ATP synthase enzymes
chloroplast DNA
- naked circular DNA not associated w histones
- used to make some of the proteins and enzymes for phot
chloroplast ribosomes
70s ribosomes allows for translation of proteins coded for by cpDNA
2 different types of chlorophyll a
- p680
- p700
p680 is in PS…
2
P700 is in PS…
1
accessory pigments
- carotenoids (reflect yellow orange)
- xanthophylls (reflect yellow)
what can you use to separate photosumthestic pigments
TLC
where does photolysis occur
PS2
Photolysis
- PS2
- splitting of water
2h20 = 4h+ + 4e- + o2
how is oxygen produced in LDR? and what happens
- photolysis of water at PS2
- diffuses out through stomata
- used for respiration
2 uses of water (ps)
- source of h+ used for photophosphorylation
- donates e- to chlorphpyll to replace those lost
non cyclic phosphorylation involves…
ps1 AND ps2
cyclic phosphorylatin involves…
ps1
STEPS of ldr (non cyclic)
- photon of light strikes PS2 (p680), energy is channelled to primary pigment reaction centre
- light energy excites a pair of electrons in the chlorophyll
- energised electrons escape chlorophyll and are captured by an electron carrier embedded in the thylakoid membrane
- electrons then replaced by electrons from photolysis
- iron ion in the Electron carrier protein is reduced to Fe2+, but can then pass it on and become reoxidised to Fe3+ and pass this to the next EC in the chain
- e- are passed down ETC and energy is released. e- eventually return to PS1
- energy from first etc used to ACTIVELY PUMP protons across the t membrane into the t space
- protons accumulate in the t space, proton gradient formed
- protons diffuse down CG through ATP synthase channels. proton motor force causes adp + pi -> atp
- protons and eectrons from PS1 are accepted by NADP to reduce it to NADPH ,(NADP REDUCTASE ENZYME)
CYCLIC PHOSPHORYLATION
- light striked PS1 so ONE ELECTRON become excited and do the ETC stuff
- NO PHOTOLYSIS OF WATER, so no h+ or o2 produced
- no NADPH made
ONLY PRODUCT IS ATP
chloroplasts in guard cells
- only do cyclic, only have PS1
- produce only ATP which brings in k+ to cells so water will enter by osmosis
overall products of LDR
- atp
- NADPH
(oxygen waste)
LIR
- co2 + RuBP(5carbons) (catalysed by RuBisCO ) forms an unstable 6 carbon compound
- breaks down into 2 x 3c compound, GP
- GP reduced to TP (atp -> adp+pi AND nadph -> nadp)
- 1/6 TP out, 5/6 used to regenerate RuBP. involves atp -> adp + pi
electron donor c vs nc
cyclic: p700 in PS1
nc: water
final electron acceptor in c vs nc
c: p700 in ps1
nc: nadp
uses of TP
- 5/6 used for regeneration of rubp
- 1/6 can form glucose, to from starch, sucrose, cellulose
- lipids
- amino acids
effect of LI on photosynthesis
- as increases, the faster the LDR
- more atp and nadph for LIR
effect of co2 on photosynthesis
- needed in LIR for CARBON FIXATION to combine w RuBP to form gp
effect of temperature
- LDR not very affected as driven by energy from light NOT ke
- calvin affected eg RuBisCO enzyme
- ALSO INC TEMP = stomata close to reduce water loss so less CO2
PRACTICAL : how to change LI
- change distance of light source
- use inverse square law. LI proportional to 1/d^2
PRACTICAL : how to change conc CO2
- add different conc of sodium hydrogen carbonate to the water. dissolves to produce co2
PRACTICAL : how to change temp
- electronic water bath
PRACTICAL : how to CONTROL temp
heat sink ; glass tank between light source and plant
PRACTICAL : how to measure rate of LDR
- Use an indicator that will accept electrons instead of NADP
purpose of adding SODA LIME
- removes carbon dioxide
how many thylakoids per granum
10-100
importance of photosynthetic pigments (5)
- absorb light
- electrons excited, raised to higher energy level
- accessory pigments pass energy to primary pigments in reaction centres
4, primary pigments are oxidised, pass on e- to ETC - for light dependent reaction
what can be used as stationary phase in TLC
silica
state exact location of photosynthetic pigments in a chloroplast
- photosytems
- in thylakoid membrane
carbohydrates during compensation point
- carbs produced by photosynthesis = carbs USED in respiration
limtiing factor defitnion (2)
- a factor that will determine the rate
- when at lower levels
describe light harvesting
- pigments in a photosythem
- pigments absorb LE
- electrons get excited and move to higher energy level
- energy passed from accessory pigment to REACTION CENTRE (primary pigment chlorophyll a)
- large range of accessory pigments allows a large range of wavelengths to be absorbed
how to increase co2 in AIR
- burning fuels
what happens w green filter on phtoosyntehseis
- chlorophyll reflects green
- little photosynthesis (no LDR)
- NO PHOTOLYSIS
- no co2 used in calvin cycle, but some produced in resp
- so increase in co2 increases aciditiy
purpose of contro (2)
- comparison
- to show that X VARIABLE is producing the effect
suggest adaptation of plants in deep water (2)
- MORE pigments as lower LI so can absorb what little light there is
- pigments that absorb shorter wavelengths that can penetrate the deeper water
3 adaptations of granum
- contain photosystems
- contain electron carriers
- larhe SA for more photosystems etc
autottroph
make organic molecules from carbon dioxide and light and water
heterotroph
feeds on and digests organic molecules made by another organism
importance of fat droplet in chloroplast
- membrane formation
CYCLIC phosphorylation key points
- only PS1
- P700
- electrons return from ETC to photosystem
- only ATP produced
NON cyclic key points
- PS2 P680 does the atp chemiosmosis, using water photolysis
- PS1 does etc, but at the end, the e- + h+ dombine with NAD to form NADH
- which then goes to calvin cycle
1 GP to 1 TP
atp => adp + pi
nadh => nad
tp to rubp how to regenerate
atp => adp + pi
