Unit 2 - Light Independent Rxn Flashcards
where does the light dependent rxn occur
Thylakoid membrane = chloroplast
what is photolysis
splitting of water into O2 and water
what did our light dependent rxn produce
ATP
NADPH2
and
O2 (waste)
Light Independent RXN
- stroma of chloroplast a series of 11 reactions uses NADPH to reduce co2 into sugar
- endergonic (energy supplied by hydrolysis of ATP)
- Calvin Cycle (11 enzymes catalyzed)
Melvin Calvin
- An American biochemist won the 1961 NP for chemistry for discovering the chemical pathway of photosynthesis using c14. he started with CO2 from the atmosphere and ended up as carbohydrates that r the principal food for animals
Plants produce…
all organic mol necessary for growth (carbs/ lipids/ proteins/ nucleic acids)
Plants need to store…
chemical energy (ATP) produced from light rxn
- more stable
- moved around plant
- saved for a rainy day
plant chemical equation
6co2 + 6h20 + light energy =
glucose (c6h1206) +602
light rxn
converts solar energy to chemical energy
-ATP = energy
-NADPH = reducing power
what can we now do?
BUILD STUFF
CO2 to C6H1206
- co2 v little chemical energy =
fully oxidized - c6h1206 lots of chemical energy = highly reduced
reduction of co2 to c6h1206 makes?
many small uphill steps
- each catalyzed by specific enzymes
-using energy stored in ATP and NADPH
From Light rxn to Calvin cycle
cc = occurse in the stroma of chloroplast and needs products of light to drive synthesis rxn to make (ATP AND NADPH)
Calvin cycle 3 phases
1) carbon Fixation
2) reduction reactions
3) regeneration of RuBP
Calvin cycle use of CO2
using carbon from CO2 e- from NADPH and energy from ATP the cycle constructs G3P which is used to build glucose and other organic mols
Phase 1: carbon fixation
at the beginning of the CC, CO2, an inorganic compound reacts w a mol of ribulose 1-5 bisphosphate (RuBP), a 5c sugar to make 3c mols of 3-phosphoglycreate.
step 1 of carbon fixation
co2 from atmosphere is added to ribulose 1,5- bisphosphate (RuBP) which ha 5c forming a 6c mol
step 2 of carbon fixation
6c is v unstable and immediately splits into two 3-phosphoglycerate (3PG)
Rubisco
- enzyme: RUBP carboxylase/oxygenase
- catalyzes first rxn: fixes carbon
- most abundant protein on earth
-undergo photorespiration
Photorespiration
when rubisco binds O2 instead of CO2 (it slows down the Calvin Cycle and wastes CO2 and ATP)
Phase 2: Reductase of G3P
Reduction:
in the second stage, ATP and NADPH r used to ocnver the 3-PGA mol into mol of a 3c sugar,
glyceraldehyde-3-phosphate (G3P)
how did phase 2 get its name
bc NADPH donates e- to or reduces, a three-carbon intermediate to make G3P
step 1 of phase 2
each mol of 3-PGA receives a phosphate group from ATP, turning into a double phosphorylated mol called 1,3-bisphosphoglycerate (leaving ADP as a by-product)
step 2 of phase 2
1,3, BPG mol r reduced. each mol gets two e- from NADPH and loses one of its phosphate group, turning into a 3c sugar called G3P (produces NADP + Pi as a by-product)
G3P
important intermediate
glucose = ?
lipids = ?
aa = ?
nucleic acids = ?
= carbs
= fats, waxes, phospholipids
= proteins
= DNA and RNA
Phase 3: RuBP regeneration
- 5 G3P r rearranged back into 3RuBP w the help of ATP
step 1 phase 3
out of every 6 G3P formed, 5 r rycled to from 3 RuBP by + of 3 ATP
step 2 of phase 3
6 rotations of CC create 1 mol of glucose. of the 12 G3P mols that r produced in 6 cycles, 10 r used to generate RuBP, and 2 r used to make one glucose
Summary of CARBON of Calvin cycle
3 CO2 combine w 3 RuBP acceptors making 6 mols of G3P
- 1 G3P exits to make glucose
- 5 G3P r recycled, regenerating 3 RuBP acceptor mols
Summary of ATP of Calvin cycle
9 ATP r converted to 9 ADP (6 during the fixation step 3, during the regeneration step)
Summary of NADPH of Calvin cycle
6 NADPH r converted to 6 NADP ( during the reduction steps)
plants use of G3P (4)
1) 50% is used for structures (CELLWALL)
2) glucose is converted for energy storage
3) 1/3 is made into starch and stored for leafs use during the night
4) 2/3 is converted to sucrose and transported to rest of plant (roots/ stem/ fruit)
supporting a biosphere
on a global scale, photosynthesis is the most important process of life on earth
each year photosynthesis… (2)
1) captures 121 billion tons of co2
2) synthesizes 160 billion ton of carbon
where in plant cells does the calvin cycle take place
stroma
what is the mol that leaves the Calvin cycle to be converted into glucose
G3P
whic part of the Calvin cycle would be affected if a cell could not produce the enzyme RuBisCO
none of the parts of the CC could take place
reactant or products of CC
1) co2
2) ATP
3) NADPH
4) G3)
1) reactant
2) reactant
3) reactnat
4) both
