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Engineering HSC and IIT-JEE Mains and
advanced videos. Hello students today we
are studying chapter photosynthesis in
that we are studying topic Dack reaction
of Calvin cycle the cycle that takes
place after sunset which is light
independent which is also called as
black Man reaction.
That reaction during the daytime the
reaction of photosynthesis that takes
place is in the presence of sunlight but
when the Sun sets when there is no Sun
present there is a photosynthesis
reaction that happens and that is Dack
reaction the reaction that happens after
sunset it is also called as C3 cycle
because the first stable product is
carboxylic acid it is also called as
Blackmun's reaction since the name of a
scientist that reaction takes place
inside stroma remember the structure of
chloroplast inside that we had pala for
Ana stroma so that reaction basically
takes place in stroma and it said stroma
there are photosynthetic enzymes which
help the dark reaction of calvin cycle
one of the enzyme is rubp that is
ribulose biphosphate carboxylase so what
are the steps of that reaction the first
step of that reaction is carboxylation
when I say carboxylation it means
addition of carbon dioxide during
photosynthesis we all know that carbon
dioxide is used and the by-product are
oxygen in this process glucose is made
so that reaction uses carboxylation that
is addition of carbon dioxide the next
step the next step is reduction
remember blink sight during cyclic
photophosphorylation that's what they
call us
ATP and NADPH now ATP and NADPH energy
molecules ATP is adenosine triphosphate
and NADP is nicotinamide adenine
dinucleotide both these energy molecules
which were formed during cyclic
photophosphorylation
I use during Calvin cycle so basically
reduction steps uses both this energy
molecule to carry out the process and
the last step really generation when I
say the word regeneration what does it
mean to regenerate it means who
get back now doing Calvin cycle there is
an enzyme are you could be used in the
first step in the last step of
regeneration anima P has to be recovered
back so that Calvin cycle continues so
let us see what would be the steps of
Calvin cycle
the steps of back reaction back reaction
has many differently the first name is
c3 cycle because carbocyclic acid or
carboxylic acid is the first stable
product like this form in that reaction
shock reaction is basically tailored in
the stroma of chloroplast whereas light
reaction on cyclic photophosphorylation
is scary
somewhere else dark reaction is also far
less biochemical things now it is what
is biochemical system because in dark
reaction rubp ensues and a UDP is
regenerated again there are chemicals
which are used to start back reaction of
Calvin cycle
the three steps of back reaction of
Calvin cycle are carboxylation which is
addition of co2 the second step is
reduction ATP and nadph on the light
reaction of photosynthesis I use in that
reaction and the third surface
regeneration of getting back off our UDP
ribulose biphosphate now we'll see what
are the chemical components and how this
calvin cycle actually takes place now we
will see what other steps of dark
reaction or you can say calvin cycle the
steps are as follows
the first step carboxylation which is
elation of carbon dioxide the
atmospheric carbon dioxide which we
exhale out or give out adds up to
rubp which's ribulose biphosphate and
this rubp is present inside the stroma
co2 plus rubp
combines under the president of enzyme
rubisco to forms a six carbon unstable
product and now this six carbon unstable
product we all know that unstable
products always want to become stable
immediately splits into two molecules of
3-pga plus three peaches and now this 3
pj is phosphor glycerol
when two molecules of 3-pga are formed
the next type of reaction takes place
which is reduction we all know that
during the light reaction of
photosynthesis ATP and NADPH form and
this ATP and NADPH
like energy molecules so your 3-pga in
the presence of ATP forms 1 comma 3 dye
PG and ATP is reduced to ADP we all know
ADP is adenosine triphosphate
from that if we remove one phosphate we
get a B 1 comma 3 dye PG in the presence
of nad p
when it gets reduced form glyceraldehyde
3-phosphate or you can say g3t and now
comes the last part of the reaction
which is regeneration we all know that
re OPP was used in the first reaction so
we have to get re OPP back in this
reaction g3p gets reduced and ru be
peaceful
basically rubp is regenerated so in the
dark-- reaction oil can recycle the rubp
which was initially used is regenerated
back we get back our you baby and kelvin
cycles goes on continuously to fix one
molecule of oxygen Calvin cycle has to
run six time so this reaction was we
have written has to be done six tends to
generate one oxygen molecule so students
this is all about Calvin cycle I hope
you are clear with the steps of Calvin
cycle and how does Calvin cycle function
thank you
