Energy Carriers
Energy Carriers
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In Photosynthesis, energy in sunlight is
used to make food.
In Respiration, food is broken down to
release energy.
Molecules ADP, NAD+ and NADP+ trap
and transfer this energy
ADP
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ADP = Adenosine DiPhosphate
This molecule is found in ALL living cells.
Adenine—Ribose—Phosphate ~ Phosphate
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Unstable bond
ADP is a low energy molecule
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ATP
ATP = Adenosine TriPhosphate
 Add another phosphate to ADP = ATP
Adenine —Ribose—Phosphate~Phosphate~Phosphate
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Extra energy in unstable bond
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Phosphorylation=adding a phosphate group
ADP + energy + P  ATP + Water
ATP is an Energy rich compound
ATP
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ATP stores energy, not for long though
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It can be moved around inside a cell
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When ATP breaks down to ADP it releases energy
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Energy released is used to carry out most reactions in the
cells.
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ATP + Water  ADP + P + energy
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Cells release energy from ATP 10 million times per second
ATP and ADP
NADP+
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NADP+ = Nicotinamide Adenine Dinucleotide Phosphate
Is a low energy molecule involved in Photosynthesis
NADP+ accepts a Hydrogen proton+ 2 electrons = NADPH
NADP+ + 2 electrons + H+  NADPH
(Low energy) (High energy)
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(High energy)
The Addition of Electrons to a molecule = Reduction
NADP+ is said to be reduced to NADPH
NADPH
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NADPH is a very High energy
molecule.
It is an electron carrier
Energy it carries is used in
photosynthesis
When it breaks down it releases
2 high-energy electrons & a
hydrogen ion
 NADPH  NADP+ + 2 electrons + H+
(High Energy)
(Low Energy)
(High Energy)
ATP Vs NADPH
NADP+ Vs NAD+
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NAD+ = Respiration
NADP+ = Photosynthesis
NAD+ is a low energy molecule just like NADP+
and changes to the high-energy molecule NADH
just like NADPH
Photosynthesis
Plants making their own food
Role of Photosynthesis
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Plants use it to make food
Animals get their food from plants
It produces oxygen which is needed to release
energy in respiration
It is responsible for forming fossil fuels
It removes carbon dioxide from the air
Photosynthesis requires:
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carbon dioxide,
water,
light energy,
chlorophyll.
Photosynthesis produces
glucose
 waste oxygen
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Photosynthesis converts
light energy
chemical energy
Stages in Photosynthesis
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Light is absorbed
- By Chlorophyll in Chloroplast
Water is split
- 2H2O  4H+ +4e- + O2
Products are produced
- Oxygen, hydrogen ion & electrons
Light energises electrons
-sunlight energises electrons through chlorophyll
Glucose is formed
- CO2 + H+ + E-  C6H12O6
Sources of Light CO2 & H2O
Light
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Sun
Artificial bulbs
Carbon Dioxide
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Animals respiring
Burning of fossil fuels
Water
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In soil due to rain or nearby rivers & lakes
2 stages of Photosynthesis
Photosynthesis
Light Stage
Dark Stage
Light Stage
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This takes place in the grana of the chloroplast
It makes energy for converting ADP + P into
ATP
It makes hydrogen ions from the splitting of
water to use in the dark stage of photosynthesis
Light stage
Light Stage
Phosphorylation
Making ATP
Photolysis
Splitting water
Photolysis
The splitting of water
Water
2H20
Hydrogen ions
4H+
Used to convert NADP
To
NADPH
Electrons
4E-
Oxygen
02
Go back to chlorophyll
By product
Excreted through leaf
Water Splitting Equation
Light
2H2O 
+
4H
+4e
+ O2
Phosphorylation
Making ATP and NADPH
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Where do plants get their energy
from?
- Sun Light
There are 7 different colours in
white light, the plant can only
absorb these if it has a pigment.
The most important pigment is
Chlorophyll because it sits next to
an electron acceptor.
The electron acceptor takes the
energy from the pigments and adds
it into electrons.
Chloroplast Pigments – In Grana
Electron acceptor
Energised electrons
passed on
Energy
Passed on
Light energy
absorbed
Pigments
Electron Flow Pathways to make
ATP & NADPH
2 Different Pathways
1.
Cyclic PhotoPhosphorylation
2.
(circle) (light) (adding a phosphate)
Non-Cyclic PhotoPhosporylation
Electron Pathway 1:
Cyclic Photophosporylation
ADP traps this energy by adding
another phosphate
Electron Acceptors
E-
E-
E-
Energy
E-
E-
Chlorophyll
Light
energy
absorbed
Energy
Energy
ADP + P
ATP + Water
Energy
Energy
Energy
Electron flow that
looses energy as it
goes around
Electron Pathway 1:
Cyclic PhotoPhosphorylation
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High energy electrons travel around a series of
electron acceptors & back again to chlorophyll
As they move around they loose energy
This energy is trapped by ADP and a
phosphate within their bonds.
This forms ATP and water.
ADP + energy + Phosphate  ATP + water
Electron Pathway 2:
Non -Cyclic Photophosporylation
Light
2E-
Electron Acceptors
O2
2H2O
4E4H+
2E-
2EADP + P
Chlorophyll
ATP + Water
2E-
Light
energy
absorbed
2E-
NADP+
NADP- + H+
NADPH
Electron Pathway 2:
Non-Cyclic PhotoPhosphorylation
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2 high energy electrons passed along at a time
through a series of electron acceptors
They loose energy as they pass from acceptor
to acceptor, this energy is used to make ATP
At the end 2 electrons combine with NADP+ to
form NADP-.
Water is split using light energy, 2 electrons
return to chlorophyll while the protons attach
to NADP- to form NADPH
Products of Light Stage
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Oxygen
ATP
NADPH
Dark Stage
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This is also known as the Calvin cycle
It takes place in the stroma of the chloroplast
It uses energy got from breaking down
ATP into ADP + P
It uses hydrogen ions and electrons got from
breaking down
NADPH into NADP+ + 2 electrons + H+
Dark Stage Calvin Cycle
6CO2
Oxygen atoms are
removed
12 Hydrogen ions
are added
Glucose is formed
C6H1206
Electrons are
added
Dark Stage Calvin Cycle
NADPH
Carbon Dioxide
NADP+
Glucose (C6H12O6)
ATP
ADP + P
Main events in photosynthesis
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Light energy is absorbed by chlorophyll
Water is split
The electrons are passed to chlorophyll
The protons are stored in the chloroplasts
The oxygen is released
Sunlight transfers energy to electrons
The high energy electrons, stored protons( the
hydrogen ions) and carbon dioxide are used to
make glucose
Light
Released
Chlorophyll
Electron Deficient
Chlorophyll
High Energy
Electrons
Water
Protons + electrons + oxygen
ADP
Proton Pool
ATP
NADP+
NADPH