Photosynthesis
6.2 Reactions of Photosynthesis
Photosynthesis
 Purpose: to use _____________________ from sunlight to create
glucose
- solar energy converted to usable chemical energy
 Occurs in the ______________________ membranes within
_______________________
 Requires 6 molecules of __________ and 6 molecules of
__________
 During photosynthesis, many complex chemical reactions form
intermediates and final ______________________ molecules
- ______________: principal energy-supply molecule for living cells
(immediate)
- _________________: electron donor in energy transfers
- ___________________: energy storage for later use by cells
ATP and NADPH
 Used by ___________ living things as an
_____________________ source of energy for cellular
functions
 Formed by addition of ___________________ group (Pi) to a
molecule of lower energy _______.
 _________________ accepts one ______________________
atom and _______ electrons to form
_____________________.
- these electrons can then be ________________ to other
molecules and NADPH becomes ____________________
again.
Reactions
 Stage 1: ____________________ solar energy and transferring it
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to ________________________
Stage 2: using captured solar energy to make ______________
and to transfer high-energy electrons to __________________;
creates _____________________ (electron carrier)
Stage 3: energy stored in ATP and electrons carried by NADPH used
to form __________________ from _______________
Stage 1 & 2: light ______________________ reactions requiring
________________________
Stage 3: light ___________________________
_________________ __________________ forming glucose
(due to carbon fixation)
Capturing Solar Energy (Stage 1)
 _________________________: clusters of
______________________ and pigment molecules
- found on thylakoid _______________________
- 2 distinct but interconnected photosystems (I & II)
 Electrons in chlorophyll capture and absorb
______________________
- electron now has ______________ amount of energy (excited
state)
 High-energy electrons move along electron
_______________________ chain
- NEED TO BE _________________________!
 ___________________________: solar energy used to split
______________ into H+ and O2 gas
- occurs in thylakoid ___________________
- 2 H2O molecules consumed for every 4 electrons transferred
Electron Transfer & ATP Synthesis
(Stage
2)Chain:
 Electron
Transport
_____________ electrons
are passed along the chain,
slowly
__________________
energy in each step
- some of this energy is
captured to make
___________
- electrons eventually rejoin
H+ to form new compounds
Electron Transfer & ATP Synthesis (Stage 2)
 Photolysis: splits __________________, electrons move into
Photosystem _________
 Electrons then passed along ETC toward the inside of the thylakoid
______________________.
- releases ___________________
- draws _______ ions across membrane toward __________
- concentration of H+ ions in lumen increases creating buildup of
_______________________ charge
 Electrons enter Photosystem ______
- replace electrons energized by __________________
 Energized electrons move through chemical complexes to
______________________
- accepts 2 high- energy __________________________ and an
________ ion; becomes __________________
- NADPH used in light-independent reaction (Calvin Cycle)
Chemiosmosis
 H+ ions pulled across membrane into ____________________
- creates concentration __________________; H+ cannot escape
unless through ___________ synthase complexes
- movement through releases _______________
 Combines __________ with _______ .... creates....
_____________!
 Recall: energy stored in H+ ion gradient derived from energy of
____________________ energized in Photosystem ______
Review Stage 2
Light-dependent reactions:
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Calvin Cycle & Carbon Fixation (Stage 3)
 Final stage of photosynthesis
- results in formation of ____________________ organic
molecules from _______ (carbon fixation)
 __________________ Cycle:
- occurs in the _____________________ of chloroplasts
- ____________ must be readily available
-utilizes both __________ and high-energy electrons on
______________ from light-dependent reactions
- makes ____________ (or _________________), a sugar used to
create ___________________
Calvin Cycle & Carbon Fixation (Stage 3)
Steps of Calvin Cycle:
 must cycle ________ times for ______ glucose to be produced
 Atmospheric __________ diffuses into chloroplast
- carbon joins 5-carbon sugar _______________ (ribulose
biphosphate)
- forms ______________________ 6-carbon sugar
 Splits into _____________ 3-carbon sugars ___________
(phosphoglyceric acid)
 PGA’s use energy of _________ to strip H from
__________________
- makes a stable 3-carbon organic compound (__________ or
_____________) and ____________________
 PGAL (G3P): some goes on to make _________________, rest
converted to __________________ to continue cycle
PGAL (G3P)
 The PGAL (phosphoglyceraldehyde) that goes on to make
_______________________ must be united with another
molecule of ___________________ in order for glucose to be
formed.
 PGAL therefore has 3 important functions:
- used for _________________________ to fuel the light
independent reaction
- some can be converted to ___________________ for energy
_______________________
- a portion is used to replenish _________________ and drive the
cycle