c1.2 - photosynthesis Flashcards
chloroplast
organelle found in plants + green algae
site of photosynthesis
structure of chloroplast
double membrane
grana - stacks of flattened disks (thylakoid) contains ps1 + ps2, ETC, atp synthase
grana connected by intergranal lamellae
stroma
- fluid filled matrix contains enzymes
where are chloroplasts located in angiosperm leaf
mainly in palisade layer
chloroplast adaptations for photosynethis
- thylakoids give large SA for light independent reactions
- photosynthetic pigments affra ged in photosys5ems to maximise light absorption
- stroma directly surrounds grana = products of photosynthesis diffuse directly into stroma
- contain DNA + ribosomes
inner membrane less permeable than outer, enabling control over movement of substances
angiosperm leaf adaptations for photosynthesis
- large SA to maximise light absorption
- think to reduce diffusion distance for co2
- upper epidermis transparent allowing light to strike mesophyll layers
- palisade cells densely packed + contain many chloroplasts
- air spaces reduce diffusion distance for co2
- vein network transports water + minerals to lead to+ takes sugars away
- stomata allow co2 to diffuse into leaf
transducer, why are chloroplasts described as transducers
- something converts one type of energy into another
- transduce light energy into chem energy of ATP
photosynthetic pigment
molecule present in chloroplasts that absorb light energy for photosynthesis
absorbs specific light wavelengths c reflects ithers
examples of photosynthetic pigments
- chlorophyll a+b
- carotenoids
- xanthophylls
why range of photosynthetic pigments
absorbs range of light wavelengths
purpose of chromatography
separates different products from a mixture of
equation used to calculate Rf
distance travelled by component
Rf = ————————————————
distance traveled by solvent
photosynthesis
complex metabolic pathway that synthesises organic molecules from co2 + water in presence of light
6CO2 + 6H2O -> C6H12O6 + 6O2
stages of photosynthesis
light dependent
light independent
photosystem
- protein complex consisting of antennae complex + reaction centre
- involved in absorption of light + transfer of electrons in photosynthesis
- two types: ps1 + ps2
difference between ps1 + ps2
absorb different light wavelengths
process of light harvesting
- antennae complex absorbs light energy of varying wavelengths + transfers it quickly and efficiently to reaction centre
- energy absorbed by two chlorophyll a molecules which emit excited electrons
absorption spectrum
pattern of bands that occurs when a substance absorbs different wavelengths of light
action spectrum
graph of rate of photosynthesis against each light absorbed by a pigment
light dependent stage
- first stage of photosynthesis
- takes place in thylakoids of chloroplast
- uses light energy t9 produces ATO, reduced NADP, and O2
sources of electrons for ETC
cyclic + non-cyclic photophosphorylation
cyclic photophosphorylation
formation of ATP involving ps1 only, where NADP is not reduced
outline cyclic photophosphorylation
- involves ps1 only
- excited electrons enter ETC.to produce ATP then return to ps1
- no reduction of NADP + no water required to replace lost electrons
purpose of cyclic photophosphorylation
produces additional ATP to meet surplus energy demands of cell
non cyclic photophosphorylation
formation of ATP + reduced NADP involving ps1 and ps2
outline non cyclic photophosphorylation
- involves ps1 + ps2
- excited electrons nested ETC to produce ATP
- NADP acts as final electron acceptor + is reduced
- water is photolysed to compensate for electrons lost for ps2
purpose of non cyclic photophosphorylation
produces ATP + reduced NADP for calvin cycle
how does chemiosmosis produce ATP in lds
- protons flow down conc gradient from thylakoid space into stroma via ATP synthase
- ATP synthase phosphorylates ADP to form ATP as protons flow through it
photolysis
splitting of molecule of water in presence of light that occurs in lds
produces protons, electrons, and o2
H2O -> 2H+ + 2e- + 1/2O2
what happens to products of photolysis
H+ - used in proton pumping and to reduce NADP
e- - replace electrons lost from chlorophyll a in ps2
O2 - byproduct, used for respiration or diffuses out of leaf as waste gas
how ETC results in production of reduced NADP
NADP acts as final electron acceptor
subsequently reduced
LIS of photosynthesis
- second stage of photosynthesis
- calvin cycle produces glucose
- doesn’t require light energy + takes place in stroma
- uses CO2 + products of LDS to build organic. ole uses
what is LIS also known as
calvin cycle
main stages of calvin cycle
- carbon fixation
- reduction
- regeneration
carbon fixation of calvin cycle
- reaction between CO2 + RuBP catalysed by enzyme RuBisCo
- forms unstable 6C intermediate that breaks down into 2 molecules of G3P
reduction of calvin cycle
- 2 G3P reduced to 2 TP
- requires 2 reduced NADP + 2 ATP formed during LDS
- forms 2 NADP + 2 ADP that enter LDS
regeneration of calvin cycle
- after 1C leaves cycle, 5C compound forms
- RuBP regenerated from 5C usuing 1 ATP
- forms 1 ADP
how are nutrients produced as a result of photosynthesis
- formation of amino acids for GP (requires nitrates + sulfates)
- TP molecules used to produce sugars
e.g: glucose, fructose, sucrose
limiting factor
variable that limits rate of reaction
limiting factors in photosynthesis, what stage limited
light intensity - LDS
light wavelength- absorption by chlorophyll
CO2 concentration - LIS
temp - enzyme controlled reactions (carbon fixation)
pH - enzyme controlled reactions
role of nitrogen in plant metabolism
synthesis of amino acids, nucleotides, + chlorophyll
what does nitrogen deficiency in plants cause
- stunted growth
- chlorosis (yellowing of leaves due to insufficient chlorophyll production)
role of magnesium in plant metabolism
central component of chlorophyll
what does magnesium deficiency in plants cause
chlorosis (yellowing of leaves due to insufficient chlorophyll production)
