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Cell Energy
Photosynthesis and Respiration
How do Cells Store Energy?


Adenosine Triphosphate (ATP) – the
molecule where the energy is stored for cell
processes.
NADP+ and NADPH- carrier molecules that
carry high energy electrons for reactions in the
cell.
ATP Model
Adenine
Ribose
3 Phosphate groups
ATP- ADP Cycle

When ATP loses a phosphate group it
releases energy and becomes ADP
(Adenosine Diphosphate).
ATP vs. ADP
compared to a battery
ADP
ATP
Adenosine diphosphate (ADP) + Phosphate
Partially
charged
battery
Adenosine triphosphate (ATP)
Fully
charged
battery
ATP-ADP Cycle
ATP is
formed
Energy is
added with a
phosphate to
ADP
Energy is
released with a
phosphate
ADP is
formed
Photosynthesis

Photosynthesis – plants trap the sun’s energy
and store it in molecules of glucose.

Process of using sun’s energy to make food for the
plant.
Photosynthesis Formula
Process of Photosynthesis
sunlight

Carbon Dioxide + Water
glucose + oxygen
chlorophyll
Reactants
Products
Photosynthesis takes place in leaves
(primarily)…

Leaves are the
major sites of
photosynthesis
(although any
green vegetation
can do so).
Within cells of the leaf, photosynthesis
takes place in the CHLOROPLASTS…
Elodea cells with small,
circular chloroplasts
Thought it didn’t go any smaller?
Within those crazy chloroplasts…

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Thylakoids: sacs
containing
chlorophyll (pancake)
Grana: stack of
thylakoid disks
(stack of pancakes)

Stroma: the region
outside the grana.
(syrup)
So where’s the juice?

Nature of Sunlight—
 Light = electromagnetic energy (radiation), travels in
rhythmic waves ( wavelengths)
 Entire range = electromagnetic spectrum
 Visible light drives photosynthesis
Photons & Pigments

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Light behaves like individual particles called
photons
Light can be absorbed, reflected, transmitted
Things that absorb —called pigments
Photosynthesis pigments:
 chlorophyll a (blue-green)
 chlorophyll b (yellow-green)
 carotenoids (yellow-orange)
Two Steps of
Photosynthesis:
1.
2.
Light Dependent Reaction
Light Independent Reaction
(also called Calvin Cycle or
Dark Cycle).

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Light-Dependent Reactions- 1st step
of Photosynthesis
Takes place in thylakoid membranes
(pancakes).
Requires light energy
Sunlight and water enter the grana as
reactants.
Oxygen is produced.
ATP and NADPH go to the Calvin
Cycle.
Sunlightreactant
Carbon
Dioxidereactant
Waterreactant
NADP+
ADP +
P
Calvin
Cycle
LightDependent
Reactions
ATP
NADPH
Oxygen- product
Glucose/Sugarproduct
2nd Step: Light-Independent
Reactions
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(Calvin Cycle/Dark Cycle)
No light required
Takes place in the stroma (syrup)
Carbon dioxide enters as reactant.
Glucose is produced.
For every 6 molecules of CO2, only one
molecule of glucose is formed.
ADP and NADP+ go to Light Dependent
Step.
Sunlightreactant
Carbon
Dioxidereactant
Waterreactant
NADP+
ADP +
P
Calvin
Cycle
LightDependent
Reactions
ATP
NADPH
Oxygen- product
Glucose/Sugarproduct
Cell Respiration
The process where food molecules are broken down
in the presence of oxygen to release energy.
 Takes place in mitochondria and cytoplasm.
 This process may be:
 Aerobic ( in the presence of oxygen)
 Anaerobic (without oxygen)
 The equation for cellular respiration is:
6O2 + C6H12O6
6CO2 + 6H2O + Energy

3 Main Stages of Cell Respiration
1.
2.
3.
Glycolysis
Krebs Cycle
Electron Transport Chain
Glycolysis
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Occurs in cytoplasm
One molecule of glucose is broken in half,
producing pyruvic acids.
2 molecules of ATP are produced
Does not require oxygen (anaerobic)
2 Pyruvic
acid
After Glycolysis
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If oxygen is present ( aerobic) the second stage
is the Krebs cycle.
If oxygen is not present, glycolysis is followed
by Fermentation.
Krebs Cycle
(also called citric acid cycle)
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At end of glycolysis about 90% of the chemical
energy from glucose is still unused. Oxygen needed
to extract that energy.
Aerobic (requires oxygen)
Occurs in mitochondria.
Pyruvic acid is broken down into carbon dioxide.
Electron Transport Chain
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Uses high energy electrons to convert ADP to
ATP
34 more ATP molecules per glucose molecule
are produced in addition to the 2 ATP
molecules produced during glycolysis.
Water is also a product.
Respiration: AnOverview
Section 9-1
Mitochondria
Electrons carried in
NADH
Pyruvic
acid
Glucose
Glycolysis
Cytoplasm
Go to
Section:
Krebs
Cycle
Electrons
carried in
NADH and
FADH2
Electron
Transport Chain
Mitochondria
Section 9-2
Flowchart
Cellular
Respiration
Glucose
(C6H1206)
+
Oxygen
(02)
Go to
Section:
Glycolysis
Krebs
Cycle
Electron
Transport
Chain
Carbon
Dioxide
(CO2)
+
Water
(H2O)
Fermentation

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Releases energy form food molecules in the
absence of oxygen (anaerobic)
The two main types of Fermentation are :


Alcoholic fermentation
Lactic Acid Feremtation
Alcoholic Fermentation
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Occurs in yeasts and other microorganisms.
Converts pyruvic acid to ethyl alcohol
Causes bread to rise
Lactic Acid fermentation
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Lactic acid is produced in your muscles during
rapid exercise.
Lack of oxygen to the muscles- causes muscle
soreness.
Pyruvic acid is converted into lactic acid
Section 9-1
Chemical Pathways
Glucose
Glycolysis
Krebs
cycle
Fermentation
(without
oxygen)
Go to
Section:
Electron
transport
Alcohol
or lactic
acid