5.2.1 Photosynthesis Flashcards
photosystem
chlorophyll and other pigments arranged in complexes with proteins such as lipids and enzymes
- contains a reaction center
what does the reaction center of photosystem contain?
chlorophyll A
what does the primary photosynhetic pigment do?
abdsorbs light energy at particular wavelength for light dependant reaction
what does action spectrum show ?
rate of photosynthesis at different wavelengths of light
what is chemiosmosis ?
movement of H+ ions through ATP synthase producing a proton motive force to form ATP from ADP and Pi
what molecule is the final electron acceptor
NADP
what molecule is dehydrogenated in non cyclic photophosphorylation
water
where does photolysis of water occur
inside the thylakoid
where does atp synthase occur
in the stroma
what molecule is hydrogenated in non cyclic photophosphorylation
NADP
which wavelenth of light does the chlorophyll absorb in photosystem 2
680nm
which wavelenth of light does the chlorophyll absorb in photosystem 1
700nm
where do protons for chemiosmois come from
from the photolysis of water
why is it called phosphorylation
your in light adding a phosphate group to make ATP
what is phosphorylated
ADP
products of non-cyclic photophosphorylation
ATP
NADPH
O2
general name of pigment complexes in non-cyclic photophosphorolyation
photosystems
why is the pH of the thylakoid lumen lower than that of the stroma
the thylakoid contains a higher concentration of H+ ions than to the stroma so more acidic= lower pH
what is the function of the pH gradient in the non-cyclic photophosphorylation
forms electrochemical gradient so chemiosmosis occurs so H+ ions move down concentration gradient through the ATP synthase to produce the protein motive force to make ATP
explanation of cyclic photophosphorylation
light energy is absorbed by photosystem 1
chlorophyll a releases an electron
shifts to electron carrier and eventually back to PS1 to replace e-
helps keep electrochemical gradient
H+ then move down conc gradient through the ATP synthase to produce ATP by chemiosmosis from ADP and Pi
products of cyclic photophosphorylation
ATP
what is the purpose of cyclic phosphorylation
to produce more ATP so there’s enough for calvin cycle
how are electrons raised to higher energy levels or excited
electrons present in pigment molecules such as chlorophyll are excited by absorbing light from the sun
- high energy electrons are released when chemical bonds are broken in respiratory substrate molecules
what are excited electrons passed into
electron transport chain and used to generate a proton gradient
what makes up an electron transport chain
series of electron carriers
what do pigment molecules do
absorb specific wavelengths of light and reflect others
what causes different colour and shades of leaves
due to the different combinations of pigments
where does the light independant reaction occur
in stroma
what impact does greater light intensity have on photophosphorylation ?
increase
what impact does greater light intensity have on ATP and NADPH production
increase
what impact does greater light intensity have on GP levels
remain the same or could increase
what impact does greater light intensity have on TP levels
increase
what impact does greater light intensity have on RuBP levels
increase
what impact does greater light intensity have on rate of photosynthesis overall
increase
what impact does lower light intensity have on photophosphorylation
decrease
what impact does lower light intensity have on ATP and NADPH production
decrease
what impact does lower light intensity have on GP levels
increase as can’t turn GP into TP
what impact does lower light intensity have on TP levels
decrease
what impact does lower light intensity have on RuBP levels
decrease or stays the same
what impact does lower light intensity have on rate of photosynthesis overall
decrease
what might limit the carbon dioxide concentration that can be taken in through the stomata
if increase transpiration - windy conditions cause stomata to close so CO2 won’t be taken in
what might limit the photosynthetic rate at high temperatures
enzyme denatures
transpiration rate
photorespiration
oxygen competes with CO2 for the active site of rubisco leading to a decrease in the fixation of CO2
what impact does a higher carbon dioxide concentration have on carbon fixation
increases
what impact does a higher carbon dioxide concentration have on GP levels
increase
what impact does a higher carbon dioxide concentration have on TP levels
could increase but would need more ATP and NADH
what impact does a higher carbon dioxide concentration have on RuBP levels
stay same or increase
what impact does a higher carbon dioxide concentration have on overall rate of photosynthesis
increase
what impact does a lower carbon dioxide concentration have on carbon fixation
decrease
what impact does a lower carbon dioxide concentration have on GP levels
decrease
what impact does a lower carbon dioxide concentration have on TP levels
decrease
what impact does a lower carbon dioxide concentration have on RuBP levels
increase as will accumulate
what impact does a lower carbon dioxide concentration have on overall rate of photosynthesis
decrease
why might enzymes and proteins be affected by high temperature
enzyme active site denatures
why is a problem if plants don’t do photosynthesis
can’t produce TP
what is a compensation point
rate of respiration and rate of photosynthesis are equal
what is DCPIP
blue indicator that accepts electrons
what can DCPIP replace in the light dependant reaction
NADP
if DCPIP replaces NADP what happens
DCPIP turns from blue to colourless
explain how pairs of electrons move from chlorophyll to electron carrier system during part of the light-dependant reaction
chlorophyll a absorbs light energy and causes e- to be excited out and be accepted by electron carrier
how are electrons lost from chlorophyll replaced
photolysis of water occurs
the H2O absorbs light and breaks down into O2 and H then the H splits into H+ and e-
explain how ATP is synthased when electrons pass through the atp synthase
electrons pass through and cause an electrochemical gradient so H+ ions move through the ATP synthase by chemiosmosis down a concentration gradient across the thylakoid membrane and causes a proton motive force
the ADP and Pi joinn to form ATP
name the enzyme responsible for fixing CO2 in the light-independant stage
Rubisco
what is light intensity measured in
Lux
what is photorespiration
rubisco can bind to either O2 or CO2
in high temp O2 levels increase so O2 outcompetes the CO2 so less carbon fixation occurs
why are high temperatures a problem for C3 plants
abobe 25 degrees photorespiration exceeds photosynthesis as oxygenese activity of rubisco increases more than carboxylase activty
so reduces rate of photosynthesis
can also denature proteins
also stomata may close due to high water loss so less CO2 enters plant
why aren’t C4 plants affected as much by high temperatures
rubsico is only in the bundle sheath so CO2 from atmosphere binds to PEP carboxylase instead and then CO2 released from their is passed to rubisco
