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bio Module 5
Photosynthesis
light-independent stage
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Created by
Emily Strozynska
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Cards (11)
Phase 1
CO2
enters leaf through
stomata
and diffuses into
stroma
of
chloroplasts
combines with
RuBP
, a 5 carbon compound
this unstable 6-carbon compound quickly breaks down into 2 molecules of a 3-carbon compound called
glycerate 3-phosphate
the enzyme
RuBisCO
catalyses the reaction between the two
phase 2
ATP
from light-dependent reaction provides energy to turn the 3-carbon
GP
into a different 3-carbon compound called triose phosphate (TP)
reaction requires H+ ions which come from reduced NADP.
Reduced NADP
is recycled to NADP
TP converted into many useful organic compounds such as
glucose
phase 3
5
out of every 6 molecules of
TP
used to regenerate
RuBP
regenerating RuBP takes rest of the ATP produced by
light-dependent
reaction
calvin
cycle
RuBP
= 5
carbons
GP
= 3 carbons
triose phosphate
(TP) = 3 carbons
Hexose = 6 carbons
where in the chloroplast does the
light-independent reaction
take place?
stroma
why the amount of
GP
increases after a
photosynthesising
plant has been in darkness for a short time
GP cannot be converted to triose phosphate since this requires
ATP
/
reduced NADP
describe the role of water in the
light-dependent reaction
of
photosynthesis
provides protons (H+ ions) for reduction of
NADP
turns in
calvin cycle
to make
hexose
calvin cycle needs 6 turns to make one hexose sugar
3 turns of cycle makes 6 molecules of
TP
- 2 molecules of
TP
are mae for every one CO2 used
5 out of 6 of these
TP
molecules use to regenerate RuBP
for 3 turns, only one
TP
produced thats used to make hexose sugar
hexose has 6 carbons, 2
TP
molecules are needed to make 1 hexose
cycle must turn 6 times to produce 2
TP
molecules to make 1 hexose
6 turns of cycle need 18 ATP and 12 Reduced NADP from light dependent reaction
calvin cycle
steps
CO2
combines with CO2 acceptor, a 5 carbon compound called ribulose biphosphate (
RuBP
). this is catalysed by enzyme
RuBisCO
RuBP by accepting carboxyl group becomes
carboxylated
, forming unstable 6 carbon compound
product of reaction is 2 molecules of 3 carbon compound
GP
. CO2 now fixed
GP reduced, using hydrogens from
reduced NADP
, to
TP
.
calvin cycle
only runs during the
day