photosynthesis
DESCRIPTION
Photosynthesis. Life in the Sun. Light is central to the life of a plant. Photosynthesis is the most important chemical process on Earth. Autotrophs are the producers of the biosphere. Plants, some protists , and some bacteria are photosynthetic autotrophs. - PowerPoint PPT PresentationTRANSCRIPT
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Photosynthesis
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Life in the Sun
Light is central to the life of a plant. Photosynthesis is the most important
chemical process on Earth. Autotrophs are the producers of the biosphere.▪ Plants, some protists, and some bacteria are
photosynthetic autotrophs. ▪ They produce the O2 for the atmosphere.▪ They provide food consumed by virtually all
organisms. Autotrophs convert light energy into chemical
signals.
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Life in the Sun
Light can influence the architecture of a plant. Plants that get adequate light are often
bushy with deep green leaves. Without enough light, plants become tall
and spindly with small pale leaves. Too much sun can damage a plant.
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Photosynthesis Overview Photosynthesis is the process by
which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide.
Carbondioxide
Water Glucose Oxygengas
PHOTOSYNTHESIS
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Photosynthesis- The Cell Structure In most plants,
photosynthesis occurs primarily in the chloroplasts of the leaf cells. A chloroplast contains:▪ Stroma (a fluid)▪ Grana (stacks of thylakoids)▪ Thylakoids (contain chlorophyll)▪ Chlorophyll (green pigment that
captures certain wavelengths of light for energy)
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Photosynthesis- The Process sunlight CO2 + H2O C6H12O6 + O2 Two linked sets of reactions:
Light Reactions▪ Convert light energy into chemical energy using
water▪ Produce O2
Calvin Cycle▪ Use chemical energy from light reaction▪ Produce sugar molecules from CO2
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Phase 1 – Light Reactions
Take place in the thylakoids which are stacked into grana
Light-absorbing pigments (chlorophyll) are found in the thylakoids.
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Phase 1 – Light ReactionsThylakoids
GOAL: CHANGE LIGHT ENERGY INTO CHEMICAL ENERGY
Absorption of light is the first step in photosynthesis.
Pigments in the thylakoid capture light energy. The light energy causes: Electrons to become excited in Photosystem II. A water molecule to split.
An electron to be released for use later. H+ to be released for use later. O2 to be released as a waste product.
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Phase 1 – Light ReactionsThylakoids
Following the electrons: Excited electrons move to an electron-
acceptor molecule in the thylakoid membrane. The acceptor molecule moves the electrons
along a series of carriers to Photosystem I. Photosystem I moves the electrons to a
protein, which transfers the electrons to a final carrier: NADP+
An energy-storing molecule NADPH is formed. Another energy-storing molecule ATP is also
formed.
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Phase 2 – The Calvin CycleStroma
GOAL: USE CHEMICAL ENERGY TO PRODUCE SUGAR
Carbon fixation: 6 CO2 molecules combine with 6 5-carbon compounds to form 12 3-carbon molecules called 3-phosphoglycerate (3-PGA).
Chemical energy from ATP and NADPH is transferred to the 3-PGA molecules to form 12 high energy molecules called glyceraldehyde 3-phosphates (G3P).
Two G3P molecules leave the cycle to be used for sugar production.
Finally, an enzyme called rubisco converts the remaining 10 G3P into 5-carbon molecules to combine with future CO2 to continue the cycle.
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Phase 2 – The Calvin CycleStroma
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An overview of photosynthesis
Light
Chloroplast
LIGHTREACTIONS
(in grana)
CALVINCYCLE
(in stroma)
Electrons
H2O
O2
CO2
NADP+
ADP+ P
Sugar
ATP
NADPH