ch 4- photosynthesis Flashcards
photosynthesis
is the process of carbon fixation:
electrons from photolysis (splitting and excitement of water from solar energy) power carbon fixation
-atmospheric carbon dioxide is reduced
-releases o2
-creates chemical energy that can be transferred through food chains
-photons used to synth sugars in photosynth
what energy producing and using recations are reverse of each other
photosynth and cellular respiration
photosynth- non spontaneous and endergonic
cellular respiration- spontaneous and exergonic
mesophyl cells
between upper and lower epidermis of leaves
-facilitate gas movement within the leaf and contain CHLOROPLASTS
where are chloroplasts found
plants
photosynth algae
NOT IN CYANOBACTERIA
membrane of chloroplasts
outer and inner
both made of phospholipid bilayer and contain intermembrane space
stroma
fluid materia that fills area inside inner membrane
location of calvin cycle
thylakoids
membrane structure within STROMA
muliple stacks form a granum
site of light dependent reactions
-the lumen is high in H+ ions
C3 vs C4 photosynth
C3- normal photosynth- three carbon PGA is formed
C4- four carbon intermediate is formed
uses spacial isolation of co2 to prevent photorespiration of plants in hot enviroment
C4 photosynth steps
-CO2 fixed and forms 4 cabon oxaloacetate - converted to malate in mesophyll cells
-malate transferred to bundle sheath cells (low in O2)
-malate decarboxylated and fixed by RuBisCo to enter calvin cycle
bundle sheath cells
leaf cells that form tightly packed layer surrounding the veins
what does CAM stand for
crassulacean acid metabolism
how does CAM photosynth work
uses temporal isolation to prevent photorespiration in hot and DRY enviroments
-stomata closed during day- prevent transpiration
-stomata open at night letting CO2 in to be fixed and form oxaloacetate and malate
-next day, stomata close, malate is decarboxylated temporally isolating CO2 from O2
-cO2 fixed by RuBisCo to enter the calvin cycle
where do light dependent reactions occur
in the thylakoid membrane
ATP generated in the light dependent reactions
is not used to power the cell, it is consumed in the calvin cycle
phoyosystems
contain special pigments like chlorophyll that absorb photons
PII- 680 and PI- 700 are used in photosynth
chlorophyl
pigment in photosystems
absorbs red and blue light and reflects green light
has a porphyrin ring with Mg bound to centre
reaction centre
pair of chlorophyl molecules in the centre of photosystems
what are the steps of non cyclic photophosphorylation
- water is split- photolysis- protons move into thylakoid lumen
- photons excite electons in rxn centre of PII- electrons go to primary acceptor
- electron goes to ETC leading to protons pumping to thylakoid lumen from stroma- then electron goes to PI to excite its pigment
- energized pigments energize electrons in reaction centre- e passed to another primary acceptor
- e passed to short ETC ending in NADP+ reductase
- protons travel down thier electochemical gradient from thylakoid lumen to generate ATP
cyclic photophosphorylation
photosystem I returns it electrons to the first ETC instead of NADP+ reducatse causing more proton pumping and more ATP production and no NADP+ production
calvin cycle
made of light indepenedent reactions- but depends on ATP and NADPH from the light dependent reactions
fixes CO2 in chloroplasts
what are the steps of the calvin cycle
carbon fixation
reduction
regeneration
carbohydrate synth
carbon fixation in calvin cycle
carbon dioxide combines with 5C RuBP
6 carbon molecule breaks into two PGA
reaction catalyzed by RuBisCo
reduction step in calvin cycle
PGA phosphorylated by ATP and reduced by NADPH forming G3P
regeneration and carb synth steps of calvin cycle
most of G3P is converted back to RuBP
while some is used to make glucose
RuBisCo
fixes CO2 to RuBP and can also
bind Oxygen to RuBP- photorespiration -
photorespiration
photorespiration - produces two phosphoglycolate that are converted to PGA
net loss of fixed carbon, no new glucose formed
C2 photosynth
what is c2 photosynth
photorespiration
