Photosynthesis Flashcards
what type of activity is photosynthesis
biosynthetic
what are two significant outcomes of PS
produces all organic material required by consumers, produces oxygen required by animals
where is photosynthesis performed
chloroplasts in green tissue of leaves
what are the parts of chloroplasts
thylakoid
granum = stacks of thylakoids
stroma = aqueous phase where many BC reactions takes place
what is the energy source of PS
sun
where is energy stored in glucose
chemical bonds within carbs
what is photosynthesis the transfer of
light energy —> chemical energy
what is oxidized/reduced in PS
water = oxidized
co2 = reduced
where is water split
H2O: O –> O2, H —> C5H12O6 and H2O
CO2: C —> C6H12O6, O —> C6H12O6 and H2O
what are the three steps of PS, where do they occur
- photochemistry (light) = thylakoid
- production of NADPH and ATP (light) = thylakoid
- incorporation of Co2 —> carbohydrate (dark) = stroma
what do pigments do in step 1
transfer radiant energy to chemical bonds
what do enzymes do in steps 2 and 3
transfer chemical energy
what is light
electromagnetic radiation characterized by its energy
what are three things that can occur when light meets matter
reflected, transmitted, absorbed
what are three classes of pigments
chlorophylls (chl a and b)
carotenoids
phycobilins (red algae and cyanobacteria, chl a and c, not b)
what can pigments do
absorb certain wavelengths of visible light, reflect or transmit the rest
why are leaves green
chloroplasts dont absorb green light, green light bounces back to eye
what is the absorption spectrum
absorbance response of a pigment exposed to a series of wavelengths of light
what is the action spectrum
physiological response of the organisms to specific wavelengths
which wavelengths are most effective for driving photosynthesis?
red and blue
which wavelength is least effective for driving photosynthesis
green
what is the difference in structure of chl a and b
chl a = ch3, chl b = cho
what is the function of the porphyrin ring in chlorophyll
light absorbing head with magnesium in the centre
what is the function of the hydrocarbon tail of chlorophyll
interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts
what is the function of conjugated double bonds in the porphyrin ring
allows electrons to flow in ring –> creates electron cloud around Mg
what happens when light hits the double bond system
1 or 2 electrons go into an excited state by absorbing the energy and emit light as photon/heat
what are light harvesting complexes
where chl a, b and carotenoids transfer energy, embedded in protein complex, link together pigments
what are light harvesting complexes connected to
reaction centres
what occurs in reaction centres
transfer of electrons to primary electron acceptor
what makes up a photosystem
light harvesting complexes and reaction centre
what is the first step in photosystem II
light excites pigment —> excited e- —. e- falls to ground state while another e- is excited —> energy passed until e- in P680 is excited
what is the second step that occurs in PSII
transfer of e- from chl a pair (P680) to primary electron acceptor
P680 —> P680+
what is the third step in PSII
e- hole in P680+ must be filled (strongest oxidizing agent) —> pulls e- from water
what is the reaction between water and P680+
H2O + 2P680+ —> 1/2O2 + 2H+ + 2e- + 2P680
what happens after PSII
ETC transfers electron down through a cytochrome complex to PSI, synthesizing ATP
what occurs at PSI
same as PSII, pigment gets excited, electron excited, energy passed through electrons until P700 is reached and transfers electron to primary acceptor
how is the whole is P700 filled
by electron coming from PS II via the ETC
what occurs after PS I
second ETC transports electron to NADP+ reductase, synthesizing NADPH
In ATP production, where is the H+ gradient, what is this process called
high in thylakoid space, low in stroma, photophosphorylation
what happens when the lights go out?
all light reactions stop, co2 absorption and sugar production continues as long as substrates are available
what are the three steps of the calvin cycle
carbon fixation, reduction, regeneration
what is the input/output of the calvin cycle
Input: 3 Co2 molecules
6 G3P molecules are made (5 stay one leaves)
Output: 1 G3P, 9 ADP, 6 NADP+
what occurs in carbon fixation
3 Co2 molecules enter one at a time and react with RuBP
what occurs during reduction
6 ATP —> 6 ADP
6 NADPH —> 6 NADP+ & 6Pi
Output: 1 G3P
what occurs during regeneration
3 ATP —> 3 ADP
how many turns of the calvin cycle are needed to generate one glucose molecule
6
what can G3P create
proteins, lipids, carbs, DNA/RNA, hormones, secondary metabolites
