Transcript adenosine triphosphate (ATP).

Photosynthesis
Plant – multicellular eukaryotes that have
cell walls made of cellulose and
photosynthesize.
“stationary animals that eat sunlight”
Adenosine Triphosphate (ATP)
One of the most important compounds that cells use.
Stores and releases energy - adenosine triphosphate
(ATP).
 ATP consists of adenine, a 5-carbon sugar called
ribose, and three phosphate groups.

Adenosine Triphosphate (ATP)
Adenosine diphosphate
(ADP) has two phosphate
groups instead of three. ADP
does not contain as much
energy as ATP. Another P is
added to ADP to form ATP.
 Cells release the energy stored
in ATP by breaking the bonds
between the second and third
phosphate groups.

Uses of ATP
Powers protein pumps in the
cell membrane
 Powers cilia and flagella
 Power for synthesis of
proteins
 Powers motor proteins that
contract muscles
 Provides cell energy

How could a small seed become a giant tree?
Heterotroph – obtains energy
from food it consumes
Autotroph – uses energy
from the sun to produce food
Photosynthesis - the process by
which autotrophs use the energy
of sunlight to produce highenergy carbohydrates that can
be used for food.
Autotroph or Heterotroph
Photosynthesis
6CO2 + 6H2O
Carbon
Dioxide
LIGHT
C6H12O6 + 6O2
Glucose
Water
Oxygen
What is Light?
Light Speed, c = 2.9979 x 108 m/s
Or 670.6 million mph
Which type of light
carries more energy, blue
or red?
Electromagnetic Spectrum
Wave length and energy are
inversely proportional
• The smaller the wave length, the
more energy
• Blue light is high energy
• Red light is low energy
Why are plants usually green?
They reflect green light
Plant Pigments

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Pigments – light absorbing molecules
Chlorophyll – the most abundant pigment
in plants, that absorbs blue and red light.
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Chlorophyll a - a blue-green pigment
Chlorophyll b - a yellow-green pigment
Accessory Pigments

Carotene - an orange pigment

Xanthophyll - a yellow pigment

Anthocyanin – a red pigment
Accessory Pigments

Why do plants need accessory pigments?

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They absorb light in other regions of the
spectrum
The accessory pigments are always present
in most plants but masked by the
chlorophyll.
Pigments

Why do leaves change color in the fall?
Answer: Shorter day lengths stop chlorophyll production,
and expose accessory pigments
Photosynthesis

Takes place in the
chloroplast
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Thylakoids – saclike
photosynthetic
membrane in the
chloroplast
Grana – stacks of
thylakoids
Stroma - the region
outside of the thylakoid
membranes
Photosynthesis (Overall)
H2O
CO2
Chloroplast
Light
NADP+
ADP
Light
+
Dark
P
CALVIN
CYCLE
(in stroma)
LIGHT
REACTIONS
(in thylakoids)
ATP
NADPH
O
Sugar
Connection between light and dark
reactions

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The electron acceptor NADP+ and ADP
enter the light reaction
NADP+ accepts 2 high energy electrons
and a hydrogen ion making NADPH.
ADP is converted to ATP
Without these products from the light
reaction the dark reaction could not
proceed.
Light-Dependent Reaction

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Inputs = Light, Water, NADP+, ADP
Occurs in the thylakoid membranes
Conversion of light energy to ATP and
NADPH
Oxygen is released through
the stoma.
Light Reaction
Light Reaction Steps
1.
2.
3.
4.
Photosystem II – light energy is absorbed and sends
electrons through electron transport chain (ETC).
Note: H2O is the source of electrons, hydrogen and oxygen
Electrons move along ETC and pump H+ into the thylakoid
space
Photosystem I – electrons are re-energized and NADP+
picks up electrons and H+ (NADPH formed)
H+ builds up in thylakoid space, exits from high to low to
stroma THROUGH ATP SYNTHASE (a turbine that adds P
to ADP = ATP)
THE DARK SIDE
Dark Reaction (Calvin Cycle)

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Takes place in the stroma
Use ATP and NADPH to make
carbohydrates

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Glucose
Starch – long chain of stored glucose.
Cellulose – tough fibers that give plants
strength and rigidity
Dark Reaction (Calvin Cycle)
(PGAL)
(PGAL)
Dark Reaction (Calvin Cycle) Steps
1.
2.
3.
4.
CO2 enters the Calvin Cycle from the atmosphere. The
enzyme rubisco combines CO2 with a 5 carbon compound
called Ribulose biphosphate (RuBP).
The result are six 3 carbon compounds that are reduced and
combine with ATP and NADPH to make Glyceraldehyde 3phosphate (PGAL), a sugar.
One PGAL leaves the cycle at midpoint and becomes the
building block for glucose
The remaining five 3 carbon compounds continue through
the cycle to reform the 5 carbon compound RuBP
Photosynthesis
H2O
CO2
Chloroplast
Light
NADP+
ADP
+ P
LIGHT
REACTIONS
(in
thylakoids)
CALVIN
CYCLE
(in stroma)
ATP
NADPH
O
Sugar
The products of the light reaction fuel the Calvin cycle.
The products of the Calvin cycle fuel the light reaction.
Factors Affecting Photosynthesis

Shortage of water
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Temperature

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H2O acts as the electron
donor in the light
dependent reaction
Photosynthesis is
controlled by enzymes
that work best between 0
C and 35 C.
Light Intensity

More light increases rate
of photosynthesis