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oxidation is the X of electrons
loss
reduction is the X of electrons
gain
reactions including both an oxidation and reduction are called..
redox reactions
product of photosynthesis
glucose C6H12O6 (and o2)
product of respiration
ATP (and (6)co2 and (6)h2o)
average solar electromagnetic energy reaching and absorbed by earth is..
160 W/m²
other sources of energy (irrelevant) the earth gets
tidal energy, cosmic rays, geothermal energy
why is sunlight the main energy source for all of earths biosphere
as solar radadiation as an energy source surpasses any others by 5 orders of magnitude (more of it)
how much of this solar radiation the earth receives is converted into chemical energy via photosynthesis?
0.1%
autotrophs meaning
organisms which obtain their energy via converting simpe inorganic compounds to organic (photosynthesis and chemosynthesis)
photoautotrophs def
(obtain energy by) use light as energy source (convert inor to org)
chemoautotrophs def
(obtain energy by) use various chemicals as source of energy (inorg to org)
heterotrophs def
organisms which obtain their energy from consuming/ breaking down organic matter
mixotrophs def
can be autotrophic and heterotrophic eg some dinoflagellates eg dinophysis
prefix ‘litho’ meaning
inorganic
what is anoxygenic/ anaerobic photosynthesis
photosyn without the production of o2, meaning water isnt used as the electron donor. here the photosynthesisers get electrons from other reduced substances
in anoxygenic photosyn, what other reduce(able) substances do organisms get electrons from
h2 (dihydrogen), s (sulfur), alcohols, acids
what organisms use anoxygenic photosynthesis
purple sulfur bacteria, green sulfur bacteria, purple non-sulfur bacteria and heliobacteria
why are chemoautotrophs important
as they provide organic, chemical energy, often in places where there isnt any/ wouldnt be any without them eg deep sea vents, deep below earths surface.
to the global nitrogen cycle
why is autotrophic carbon fixation important
as it provides organic carbon used by all life on earth
whats is photosynthesis the conversion of (what to what)
light energy to chemcial energy AND simple molecules into complex molecules
what is respiration the conversion of
complex molecules into simple molecules
the two components of the photosynthesis reaction
the light, and light independant reaction
simply, what happens in the light reaction
the photolysis of water (oxidation of water (as water loses electrons)), and oxygen becomes a waste product
equation for the light reaction
2H2O + light → O2 + 4H+ (protons) + 4e
what are hydrogen ions essentially
protons
essentially/ simply what happens in the light indepedant reaction
CO2 is fixed into organic molecules (carbs/ glucose) using ATP and NADPH.
equation for light independant reaction
CO2 + 2H+ + 2e → CH2O (glucose)
where does photosynthesis occur (in eukaryotic cells)
light reaction occurs in the thylakoid membrane, light independent reaction occurs in the chloroplasts stroma
what is the electron donor in photosynthesis?
water/ H2O
what is the electron acceptor in photosynthesis?
NADP+ (forms NADPH after accepting electron)
products of the light reaction
ATP, NADPH (and irrelevant O2)
what happens to NADPH in the light independant reaction
oxidised (so loses an electron) to regenerate NADP+ and the electrons and protons from these conversions are used to convert CO2 into glucose
4 phases of the light independant reaction
carboxylation, reduction, regeneration and product synthesis
what happens in the first stage of the LIR - carboxylation?
the enzyme rubisco is used to catalyse the fixation of CO2 into a 6 carbon molecule by adding it to a 5 carbon molecule (RuBP). This 6c mol is unstable so quickly converts into 2, 3c mols
what happens in the 2nd stage of the LIR - reduction?
the 2, 3c mols are reduced (gain an electron) using energy from ATP and NADPH to form a sugar intermediate mol
what happens in the 3rd stage of the LIR - regeneration?
the sugar intermediate mols produced in reduction stage, regenerate RuBP (the 5c mol) so the cycle can continue
what happens in the 4th stage of the LIR - product synthesis?
the remaining sugar intermediate mols from reduction stage are synthesized to form a 6c sugar eg glucose, sucrose etc. these sugars can then be converted into fats, amino acids etc
products of the LIR
sugar eg glucose, ADP and NADP+
how many photons are needed for the LIR
8 photons
