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8.2 Photosynthesis
How do plants get energy?
What factors effect photosynthesis?
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Objectives12a) I can describe the role of ATP in cellular
activities.
12b) I can explain where plants get the energy they need to
produce food.
13a) I can explain the role of light, pigments, and electron
carrier molecules in
photosynthesis.
13b) I can state the overall equation for photosynthesis.
14a) I can describe what happens during the light-dependent and
light-independent
reactions.
14b) I can identify factors that affect the rate at which
photosynthesis occurs.
15a) I can explain where organisms get the energy they need for
life processes.
15b) I can define cellular respiration and compare it to
photosynthesis.
16a) I can describe what happens during glycolysis and the Krebs
cycle.
16b) I can explain how high energy electrons are used by the
electron transport chain
and identify how much ATP cellular respiration generates.
17a) I can explain how organisms get energy in the absence of
oxygen.
17b) I can identify the pathways the body uses to release energy
during exercise.
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An Overview of PhotosynthesisPhotosynthesis uses the energy of
sunlight to convert water and carbon
dioxide into high-energy sugars and oxygen.
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Chloroplasts
● Chloroplast - organelle where photosynthesis occurs. ●
Thylakoid - a photosynthetic structure within the chloroplast. ●
Grana - stacks of thylakoids ● Stroma - fluid portion outside of
thylakoid
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High-Energy Electrons
● NADP+ (nicotinamide adenine dinucleotide phosphate) is an
energy carrier molecule.
● NADP+ accepts and holds two high-energy electrons, along with
a hydrogen ion (H+). In this way, it is converted into NADPH.
● NADPH can then carry the high-energy electrons to chemical
reactions elsewhere in the cell.
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Lets Draw!
What is really going on in a chloroplast? (p. 111)
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Lets Draw!
What is really going on in a chloroplast? (p. 111)
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Energy Collection
Because light is a form of energy, any compound that absorbs
light absorbs energy. Chlorophyll absorbs visible light especially
well.
When chlorophyll absorbs light, a large fraction of the light
energy is transferred to electrons. These high-energy electrons
make photosynthesis work.
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Light-Dependent Reactions
● Photosynthesis involves two sets of reactions.● The first set
of reactions is known as the light-dependent reactions
because they require the direct involvement of light and
light-absorbing pigments.
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Light-Dependent Reactions
● Light-dependent reactions use energy from sunlight to produce
ATP and NADPH. ● These reactions take place within the thylakoid
membranes of the chloroplast.● Water is required as a source of
electrons and hydrogen ions. Oxygen is released
as a byproduct.
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Light-Independent Reactions
Plants absorb carbon dioxide from the atmosphere and complete
the process of photosynthesis by producing sugars and other
carbohydrates.● Light-independent reactions - ATP and NADPH
molecules produced in
the light-dependent reactions are used to produce high-energy
sugars from carbon dioxide.
