photosynthesis Flashcards
use of energy from sunlight to form carbohydrates, performed by autotrophs
photosynthesis
specializes for photosynthesis
mesophyll cells
pores where gas exchange occurs
stomata
organelles in mesophyll cells where photosynthesis occurs, contain outer, inner and intermembrane space
chloroplasts
thick enzyme rich liquid that fills chloroplast
stroma
in stroma, interconnected flattened membrane sacs that contain chlorophyll
thylakoids
stacked parcel like structures
grana
grana connectors, unstacked thylakoids
lamella
liquid filled space between thylakoid membranes
thylakoid lumen
absorbs light im blue violet & red regions and reflects and transmits green light
chlorophyll colour
primary pigment, with METHYL group
chlorophyll a
accessory pigment, with ALDEHYDE group
chlorophyll b
porphyrin rinf with magnesium @ centre and a long hydrocarbon tail
structure of chlorophyll
reflect yellow orange red
carotenoids
reflect yellow orange
flavonoids
reflect yellow
xanthopylls
reflect red violet blue
anthocyanins
convert solar energy to chemical energy, produce ATP and NADPH
light dependent reactions
makes sugar from carbon dioxide
light independent reactions (calvin cycle)
photoexcitation, electron transport, chemiosmosis
stages in light dependent reactions
antenna complex with hundreds of accessory pigment molecules and reaction center of one or more chlorophyll a molecules
photosystem
photon strikes pigment in ground state its electron undergoes excitation, electron transferred along antenna complex, until reaction center then electron is transferred to a primary electron acceptor which causes chlorophyll to be oxidized and primary electron acceptor to be reduced
photoexcitation
occurs in some bacteria, involves photosystem I, reaction centre of photosystem I is P700, photon energizes antenna complex & transfers electron to p700 gets excited, electron goes to primary electron acceptor ferredoxin, p700 oxidized, ferredoxin reduced
cyclic electron flow 1
chlorophyll a
reaction centre
part of electron transport chain, proton pump
b6f complex
occurs in photosynthetic plants
non cyclic electron flow
how electrons are replaced in photosystem 2, water split into oxygen, H+ and 2 electrons, oxygen is released, H+ added to protein gradient and electrons replace lost ones in p680
z protein
light independent reactions, occur in the stroma of the chloroplast, ATP and NADPH from light dependent used as reactants to reduce co2 into glucose (g3p)
calvin cycle
carbon fixation, reduction, regeneration of RuBP
calvin cycle stages
large enzyme, works very slowly, most abundant protein on earth
rubisco
when O2 is more plentiful in atmosphere than CO2, it binds more often and more easily to rubisco, occurs in light, does not produce ATP or sugar
photorespiration
evolutionary photosynthesis environment used to have higher CO2 than O2 and active site of rubisco would take CO2, now O2 has increased and it binds more easily w rubisco
photorespiration occurs bc?
hot dry day will drain up to 50% if carbon fixed by calvin cycle, will close stomata to prevent water loss but this limits photosynthesis, causing O2 to build up
photorespiration problem
use calvin cycle to fix carbon, lose 25-50% of fixed carbon to photorespiration, evolve to live in moderate climates (15-25C) e.g. deciduous and coniferous trees rice wheat barley
c3 plants
optimal temp 30-47C, live in tropical climates, incorporate CO2 into 4C organic compounds in mesophyll cells, uses PEP carboxylase which has a very high affinity to CO2 and cna fix CO2 even when levels are low, CO2 exported to bundle sheath cells which stores it
c4 plants
cell to cell connections
plasmodesmata
store water, optimal temp is 35C or higher, during night they open stomata and take in CO2, PEP carboxylase used to form organic acids, in day stomata is closed to prevent CO2 entering cells and water loss, calvin cycle occur
CAM plants
