Photosynthesis Flashcards
granum
inner part of chloroplasts made of stacks of thylakoid membranes where the light-dependent stage takes place
photosynthetic pigment
pigment that absorbs specific wavelengths of light and traps the energy associated with light
photosytem
system of photosynthetic pigments found in thylakoids- each contains 300 molecules of chlorophyll that trap photons and pass energy to a primary pigment reaction centre (chlorophyll a)
stroma
fluid-filled matrix of chloroplasts where light-independent stage takes place
thylakoid
flattened membrane-bound sac found inside chloroplasts- contains photosynthetic pigments/photosystems and site of light-dependent
electron carriers
molecules that can accept one or more electrons and then donate them to another carrier e.g. ferredoxin, NAD, NADP
NADP
a coenzyme and electron and hydrogen carrier
photophosphorylation
generation of ATP from ADP + Pi in the presence of light
calvin cycle
metabolic pathway of light-ind stage to make organic compounds
GP
intermediate compound in the calvin cycle
RuBP
a five-carbon compound present in chloroplasts, a carbon dioxide acceptor
TP
a three-carbon compound and product of calvin cycle used to make other larger organic molecules
autotroph
organisms that use sunlight to synthesise large organic molecules from simple organic molecules which form the building blocks of living cells
heterotroph
an organism that ingest/absorbs organic carbon to produce energy and synthesise
chemotroph
organisms that obtain energy through a chemical process (chemosynthesis) rather than photosynthesis
photoautotroph
organisms that photosynthesise because they use light as a source for autotrophic nutrition
photon
a particle of light, each containing an amount of energy
products of photosynthesis
monosaccharide sugar, converted to disaccharides for transport, to starch for storage
how to photosynthesis and respiration interrelate
both cycle oxygen/co2 in the atmosphere, products of one are the raw materials of the other
intensity of light has to be sufficient to allow photosynthesis at a rate that replenishes….
carbohydrate stores used up by respiration
plant reaches its compensation point when….
photosynthesis and respiration proceed at the same rate so there is no net gain/loss of carbohydrate
compensation period
time it takes to reach its compensation point- different for diff species
how do shade plants utilise light of lower intensity
they reach the compensation point sooner when exposed to light after being in darkness
photosynthetic pigments
pigment that absorbs light of a particular wavelength and reflects other wavelengths, appearing the colour it is reflecting to our brain/eyes
the energy associated with the wavelength is funnelled down to the primary pigment reaction centre
photosystems
funnel-shaped structures found within the thylakoid membranes of each chloroplast
chlorophylls
a mixture of pigments- porphyrin group which is a magnesium atom + long hydrocarbon chain
e.g. chlorophyll a (P680/P700), chlorophyll b
types of accessory pigments
carotenoids, xanthophylls
where does the light-dependent stage occur
grana in the chloroplasts
4 processes in the light-dependent stage
light harvesting at the photosystems
photolysis of water
photophosphorylation (ATP production)
formation of reduced NAD
photosystem 1
pigment is a type of chlorophyll a, peak absorption of red light is 700nm
photosystem 2
pigment is a type of chlorophyll a, peak absorption of red light is 680nm
photolysis
when the presence of light splits water molecules into protons, electrons, oxygen with an enzyme in PSII
non-cyclic photophosphorylation
involves PSI and PSII, produces ATP, oxygen, reduced NADP
cyclic photophosphorylation
only PSI produces ATP but smaller quantities than non-cyclic
where does the light-independent stage take place
stroma of chloroplasts
why does the light-independent stage only run in daylight
products of the l-d stage are continuously needed for the Calvin cycle to run and hydrogen ions are pumped into the thylakoid spaces so conc. of free protons in stroma falls, raising pH
role of CO2 in the light-independent stage
fixation of co2 in stroma maintains a concentration gradient that aids diffusion
converted to organic molecules in Calvin cycle
limiting factor
when the rate of a metabolic process depends on a number of factors and is limited by the factor at its least favourable level
factors that affect photosynthesis
light intensity, carbon dioxide conecentration, temperature, water stress
