10/6/15 PHOTOSYNTHESIS
CONVERTING LIGHT ENERGY TO CHEMICAL ENERGY
PHOTOSYNTHESIS
•  Where did this
redwood tree and
saguaro cactus
come from?
•  Where did the
molecules that
make up the cells
that make up the
plants come from?
PHOTOSYNTHESIS
•  Plants use water +
carbon dioxide to make
sugar
•  Plants use sugars as
material for building
cells and energy to run
cells
•  Humans use sugars for:
•  Food
•  Shelter
•  Energy
•  Clothing
•  Medicines
1 10/6/15 PHOTOSYNTHESIS OVERVIEW
•  Occurs in the leaves of green
plants
•  Occurs in specific cells in the
middle layer of the leaf
•  Occurs in organelles – called
chloroplasts – within the cells of
that layer
Products and Reactants
(6) CO2 + (6) H2O + light energy
(1) C6H12O6 + (6) O2
PHOTOSYNTHESIS OVERVIEW
•  Light-dependent reactions convert light energy to
chemical energy
•  Light-independent reactions convert CO2 to sugar
LIGHT DEPENDENT REACTIONS
•  Use the following resources: textbook; reading
analysis; this power point; internet (esp. videos)
•  Construct a concept map of the light dependent
reactions
•  A concept map makes connections between
important terms and identifies those connections
with verbs
•  Use the following terms:
•  Chlorophyll; light energy; water; H+ ions; electrons; oxygen;
ADP; ATP; NADP+; NADPH; thylakoid space; thylakoid
membrane; electron transport chain
2 10/6/15 LIGHT DEPENDENT REACTIONS
•  Also called light reactions or photochemical reactions
LIGHT DEPENDENT REACTIONS
Water + Light ➜ ATP + NADPH + Oxygen
•  Light energy is
attracted by
chlorophyll pigments
•  Energy splits H2O into
(2) H+ + O + (2) e–
•  O2 is released as
waste
LIGHT DEPENDENT REACTIONS
Water + Light ➜ ATP + NADPH + Oxygen
•  H+ collects in the
thylakoid
membrane
•  Movement of H+
helps to make ATP
•  H+ combines with
NADP to make
NADPH
•  NADPH and ATP
are used in dark
reactions
3 10/6/15 LIGHT DEPENDENT REACTIONS
Water + Light ➜ ATP + NADPH + Oxygen
•  e– (electrons) are
used by electron
transport chain
•  Movement along chain
moves more H+ into
thylakoid
•  Used to combine NADP
and H+ into NADPH
•  NADPH and ATP are
used in dark reactions
LIGHT DEPENDENT REACTIONS
•  Light Dependent Reactions Video
•  http://www.youtube.com/watch?
v=BK_cjd6Evcw&list=PL485BEC8A3222F264
LIGHT INDEPENDENT REACTIONS
•  Use the following resources: textbook; reading
analysis; this power point; internet (esp. videos)
•  Construct a concept map of the light dependent
reactions
•  A concept map makes connections between
important terms and identifies those connections
with verbs
•  Use the following terms:
•  Carbon dioxide (1-carbon molecule); NADPH; NADP+; ADP;
ATP; stroma; carbon fixation; reduction; regeneration; C5
sugar; C3 sugar; C3 sugar
4 10/6/15 LIGHT INDEPENDENT REACTIONS
(3) CO2
(3) C6
Sugar
(3) C5
Sugar
(6) C3
Sugar
ATP
NADPH
ATP
(5) C3
Sugar
(6) C3
Sugar
(1) C3 Sugar
LIGHT INDEPENDENT REACTIONS
•  Also called dark reactions, Calvin cycle or photochemical reactions
•  Three phase cycle that starts and finishes with a 5-carbon molecule
LIGHT INDEPENDENT REACTIONS
ATP + NADPH + Carbon Dioxide ➜ Glucose
•  Stage 1 – Carbon
Fixation
•  1-carbon (CO2) added
to a 5-carbon with help
of enzyme rubisco
•  6-carbon molecule
breaks into (2) 3carbons
5 10/6/15 LIGHT INDEPENDENT REACTIONS
ATP + NADPH + Carbon Dioxide ➜ Glucose
•  Stage 2 –
Reduction
•  H+ added from
NADPH
•  P added from
ATP
•  This ‘energizes’
the 3 carbon
LIGHT INDEPENDENT REACTIONS
ATP + NADPH + Carbon Dioxide ➜ Glucose
•  Stage 3 –
Regeneration
•  3 carbon sugar is
removed
•  5-carbon molecule
is restored (using
ATP)
•  Cycle must
complete (2)
rotations to make
(1) glucose
molecule
LIGHT INDEPENDENT REACTIONS
•  Light Independent Reactions Video
•  http://www.youtube.com/watch?v=o1I33Dgcc_M
6 10/6/15 COMPARING LIGHT DEPENDENT AND
LIGHT INDEPENDENT REACTIONS
•  Construct a Venn diagram comparing the two parts
of photosynthesis
•  Use the following terms:
•  Light energy; chemical energy; ATPèADP; ADPèATP; ATP;
NADPH; NADPèNADPH; NADPH èNADP; H+; e-; CO2; H2O;
thylakoid; stroma; chlorophyll; C6H12O6; electron transport
chain; Calvin cycle
7