photosynthesis Flashcards
Joseph priestly
in 1770 revealed the essential role of oxygen in the growth of green plants, inn 1774, hypothesised that plants restore the air that animals breath in and burning candles remove
Joseph priestly
in 1770 revealed the essential role of oxygen in the growth of green plants, inn 1774, hypothesised that plants restore the air that animals breath in and burning candles remove
jan ingenhouz
showed that sunlight is essential to the plant process and with the help of an aquatic plant revealed that it is only the green parts of plant that release oxygen
julius von sachs
1854 revealed that glucose in the form of starch is formed in chloroplasts in green parts of plants
t.w englemann
split light into spectral components then illuminated green algae cladophora and saw that oxygen evolved in the places of blue and red region of light, action spectrum of photosynthesis described, as well as of chlorophyll a and b
cornelius van niel
on his studies of purple and green bacteria, demonstrated that photosynthesis is a light dependent reaction in which hydrogen from a suitable oxidisable compound reduces co2 to carbs, oxygen evolved comes from h20 not co2
mesophyll cells have a large number of
chloroplasts
position of chloroplasts with respect to chlorophylls
usually align themselves wala of mesophyll cells such that they get maximum incident
labour in chloroplasts
clear division of labour in chloroplasts
system responsible for trapping light energy and synthesizing atp and nadp
membrane system
light reactions
trapping light energy, atp and nadp synthesis
enzymatic reactions synthesizing sugar which is formed into starch occurs in
stroma
dark reactions
enzymatic reactions synthesizing sugar and forming starch
light reactions are also called; dark reactions are also called
photochemical ; carbon reactions
are dark reactions light dependent or independent
dependent on the products of light reaction, atp and nadp
chlorophyll a
bright or blue green
chlorophylls b
yellow green
xanthophylls
yellow
carotenoids
yellow to yellow orange
what are pigmentw
substances that have an ability to absorb light at different wavelengths
photosynthesis occurrs in the range
400-700 nm- photosynthetic active radiation
where is chlorophylla effective
more effective in red region than blue region
maximum absorption takes place
in blue and red region
chief pigment associated with photosynthesis
chlorophyll a
accessory pigments
thylakoid pigments like chlorophyll b, xanthophylls, carotenoids, absorb light and transfer energy to chlorophyll a, enable wider range of wavelength of incoming light to be utilised for photosynthesis, protect chlorophylls a firm photo oxidation
what is photoxidation
damage to others due to high light intensity
light reactions include
light absorption, water splitting, oxygen release, formation of high energy chemical intermediates atp and nadph
pigments system are divided into two parts
light harvesting complex and reaction centre
LHC is associated with
ps1 and ps2
components of lhc
made up of accessory pigments molecules bound to proteins
ps of lhc has all pigments
except a forming an lhc also called as antenna
function of lhc
help to make photosynthesis more efficient by absorbing light at different wavelengths
reaction centre is composed of
chlorophylls a
chlorophylls a converts
light energy to chemical energy
the reaction centre is different/same
different in both photosystems
in ps 1 chlorophyll a has absorption peak at
700 nm
at ps 2 chlorophyll had absorption peak at
680 nm
electron transport system is also called as
oxidative phosphorylation
fixed electric carrier
cytochrome b-6f
mobile electron carrier
plastoquinome
copper containing mobile electron carrier
plastocyanin
primary electron acceptor in ps2
pheophytin
primary electron acceptor in ps 1
ferrodoxin reducing substrate
movement of electrons in non cyclic ets
downhill in terms of oxidation reduction or redox potential scale
which has higher redox potential frs or pheophytin
frs
nadph is reduced to nadp + h where is the h displaced
pumped to stroma
function of plastoquinome
pumped h+ from stroma to lumen
electron from frs is passed onto ; effect
nadph ; reduced to nadp+h
z schemes shaped is formed when electron carriers are arranged in
sequence of redox potential scale
splitting of water is associated with
ps2
net products of photosynthesis
oxygen
electrons needed to replace those removed by ps 1 is provided by
ps2
splitting of water occurrs
inner side of thylakoid membrane
living organisms extract energy from oxidisable compound and store in form of
bond energy
process by which atp is synthesized by cell is called
phosphorylation
phosphorylation occurrs in
mitochondria and chloroplast
photo phosphorylation
synthesis of atp and adp and inorganic phosphate in presence of light
which ps works first in photo phosphorylation
ps 2
when is atp formed in z scheme
when electron is carried from plastoquinome to cyt-b6f
when only ps 1 is functional electron transport chain
circulated through cyclic form
where does cyclic phosphorylation occur
stroma lamellae
ps 1, 2 is present/absent in
both present in membrane and grana membrane but stroma lamellae membrane lacks ps 2 and nadp reductase enzyme
does cyclic ets result in nadph synthesis
no
range in which cyclic phosphorylation occur
above 680 nm
chemiosmotic hypothesis
explaine how atp is synthesized in chloroplasts, given by p Mitchell
atp synthesis is linked to
development of proton gradient across thylakoid membrane
protom accumulation in photosynthesis is towards
inner side of thylakoid membrane
splitting of water place
on inner side of thylakoid membrane
h or proton produced by splitting of water accumulates in
lumen of thylakoid
primary acceptor of electron is located in
outer side of membrane
h from plastoquinome is released in
inner side of lumen of thylakoid
nadp reductase is located
on stroma side of thylakoid membrane
with the proton gradient there is a measurable decrease in
ph of lumen
breakdown of proton gradient leads to
atp synthesis
the gradient is broken due to
movement of protrons from stroma through transmembrane channel of CF0 of atp synthase
atp synthase enzyme consists of two parts
cf0, Cf1
cf0
embedded in thylakoid membrane , carries out facilitated diffusion is proton
cf1
protrudes on outer surface, faces stroma
breakdown of gradient; cf1
provides enough energy to cause a confirmational change in cf1 which makes the atp synthase synthesizer several molecules of atp
chemiosmosis requires
a proton gradient, pump, atp synthase, membrane
energy is used to
pump protons, make a gradient or a high concentration of protons in lumen
chemical intermediates in chemiosmotic
atp and nadph are used immediately in the biosynthetic reaction in stroma
result of o2 after light reaction
diffuses out of chloroplast
biosynthetic phase of photosynthesis
synthesis of sugar
dark reaction also carried
biosynthetic phase
biosynthetic phase is dependent on
products of light reaction atp nadp ,co2 and water
what led to the discovery of the first co2 fixation product
the use of radioactive c14 in algal p photosynthesis
what was the first co2 fixation product
3 carbon organic acid
3 carbon organic acid
3 phosphoglyceric acid
4 carbon organic acid as the product o of co2 fixation
oxaloacetic acid
co2 assimilation is of two types
c3 and c4 pathway
c3 pathway
co2 fixation product is 3c
c4 pathway
co2 fixation product is 4c
how many carbon atoms would a molecule have which after accepting co2 has 3 carbons of pga
5 carbon RuBP
Calvin cycle occurrs in what manner
cyclic
what is regenerated in calvin cycle
RuBP
in which plants does calvin cyclce occur
all p photosynthetic plants
three steps of calvin cycle
carboxylation, reduction , regeneration
what is carboxylation
fixation is co2 into a stable organic intermediate
most crucial step of calvin cycle involves
fixation of co2 for RuBP, carboxylation
carboxylation of RuBP is catalysed by
RuBP carboxylase
carboxylation of RuBP results in
formation of 2 molecules of 3pga
nature of RuBP carboxylase
oxygenation and carboxylation c/a RuBP carboxylase- oxygenase
steps that lead to formation of glucose
utilisation of 2 molecules of atp for phosphorylation and two of nadph for reduction per co2 molecule fixed
how many molecules of co2 ,atp and nadph and turns are required for formation of one molecule of glucose
6 co2 molecule, 2 atp per molecules of co2=12 atp, 2 nadph per molecule of co2= 12 nadph, 6 turns of cycle
regeneration of component is crucial if the cycle is to continue uninterrupted
co2 acceptor molecule RuBP
regeneration step requires how many atp, and what for
1 atp for phosphorylation to form RuBP
for every co2 molecule entering the calvin cycle , atp, nadph required
3 atp and 2 nadph are required
how many molecules of atp are required to make 1 glucose
18 atp
how many molecules of nadph are required to make 1 glucose
12 nadph
how many co2 are fixated to make 1 glucose
6 co2
c4 pathway occurs in plants which live in
dry tropical regions
main biosynthetic pathway is c4 plants
c3 cyclce
how are c4 plants different than c3 plants
different leaf anatomy, tolerate higher temperature, lack photo respiration, respond at higher light intensity, greater productivity of biomass
particularly large cells around vascular bundle on c4 plants
bundle sheath cells
leaves having bundle sheath cells around vascular bundle
kranz anatomy
bundle sheath cells
May form several layers around vascular bundle, large number of chloroplasts, no intercellular spaces, thick walls impervious to gaseous exchange
examples of c4 plants
maize, sorghum
c4 pathway also called
hatch and slack pathway
primary co2 acceptor molecule in c4 pathway present in
pep, present in mesophyll cells
pep undergoes carboxylation form; under influence of enzyme
oaa;pep carboxylase
mesophyll cells lack
rubisco enzyme
bundle sheath cells lack
pepcase enzyme
oaa forms ____ in c4 pathway
malic or aspartic acid in mesophyll cells
malic/Aspartic acid is transported to
bundle sheath cells
c4 acid decarboxylated to form
3c molecule and co2
3c molecule is transported back to
mesophyll where it is converted to pep again
the co2 released in bundle sheath cells enters
c3 pathway
where does calvin pathway occurs in c3 plants
all mesophyll cells
where does calvin pathway occurs in c4 plants
only in bundle sheath cells
rubisco is characterized by
the fact that it’s active site can with both co2 and o2
rubisco has greater affinity for___ under the condition
co2 when the ration ratio of co2 and o2 is nearly equal
binding of rubisco with co2 or o2 can be described as
competitive
what determines whether co2 binds with rubisco or o2
relative concentration of o2 and co2
in c3 plants rubisco binds with o2 hence
co2 fixation is decreased
in photo respiration rubp binds with o2 to form
1 molecule of phosphogllycolate, and phosphoglycerate(2c)
photorespiration does not lead to synthesis of ; instead
atp, sugar; results in release of co2 with utilisation of atp
why does photorespiration not occur in c4 plants
they have a mechanism that increases the intracellular concentration of co2 at ensure site this occurs when c4 acid is decarboxylated in bundle sheath cells to release co2
what does the i inactivity of photorespiration ensure
that rubisco functions as a carboxylase- minimising oxygenase activity
photorespiration can be called as
wasteful oxygenation reaction
how do the internal and external factors affect photosynthesis
simultaneously when a plant photosynthesizes
rate of photosynthesis is very important in determining
the yield of plants like crop plants
photosynthesis is under the influence of several factors both
internal (plant) and external
plant factors includw
number, age, size, orientation of leaves, mesophyll cells, chloroplasts, internal co2 concentration, amount of chlorophylls
internal factors are dependent on
genetic disposition and growth of plant
external factors include
availability of light, temperature, co2 concentration and water
rate of photosynthesis at any point is determined by
the factor available at sub optimal levels
what kind of relation does incident light have with co2 fixation rates at low light intensity
linear relationship
light saturation occurrs at
10 percent of full sunlight
light is rarely a limiting factor except for
plants in shade, dense forests
increase incident light beyond a point causes
breakdown of chlorophylls a and decrease in photosynthesis
co2 as a factor
Major limiting factor
concentration of co2 in atmosphere
0.03 to 0.04 percent
increase in concentration of co2 upto 0.05 percent can cause
increase in co2 fixation rates and beyond this level become damaging for longer periods
at low light intensity which group responds to high co2 concentration c3,c4
none
at high light intensity which group shows increase in rate of photosynthesis due to high co2 concentrations
both
c4 plants show saturation at about
360
c3 plants show saturation at
beyond 450
c3 plants ability to respond to higher cimo2 concentration leads to
higher productivity due crops such as tomato and bell pepper
dark reactions are controlled by
temperature
light reactions are also temperature controlled but
are affected at a much lesser extent
c4 plants respond to which temperature for higher rate of photosynthesis
higher temperature
c3 plants show higher rate of photosynthesis in temperature optimum
low temperature
effect of water as a factor is more
through its effect on plant rather than directly on photosynthesis
effect of water as a factor on plant
water stress causes stomata to close, reducing co2 availability, makes leaves wilt, reducing surface area of leaves and reducing metabolic rate
