Transcript Photosynthesis lecture

PHOTOSYNTHESIS
Autotrophs
• Are organisms
that are able to
synthesize their
own food from
inorganic
substances using
sunlight for
energy.
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Heterotrophs
• Heterotrophs are
organisms that can NOT
make their own food
• They NEED the
autotrophs as a source of
“organic macromolecules
that contain energy” AKA
Food!
Heterotrophs can NOT directly use the sun’s energy
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What is Photosynthesis?
• An anabolic, endergonic, carbon
dioxide (CO2)-requiring process that
uses light energy and water (H2O)
to produce organic macromolecules
(e.g. Glucose and starch).
6CO2 + 6H2O  C6H12O6 + 6O2
Sunlight
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Where in plants does
photosynthesis occur?
• Photosynthesis takes place in
any cell of a plant that is
green (mostly the cells in
the leaves)
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Structure of a Leaf Cell
Chloroplast
[The green part]
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The Chloroplast
• The structure within a cell (organelle) where photosynthesis takes
place.
• Thylakoids: Disk shaped membranes containing photosynthetic
pigments. Site of light dependent reactions.
• Grana: Stacks of thylakoids.
• Stroma: Fluid filled space surrounding grana. Site of light
independent reactions.
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Pigments
• In addition to water,
carbon dioxide, and light
energy, photosynthesis
requires Pigment
molecules.
• Chlorophyll is the
primary light-absorbing
pigment in autotrophs.
• Chlorophyll is found
inside the thylakoids
[inside the chloroplast].
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Light & Pigments
• Photons of light “excite”
electrons in the plant’s pigments
• Excited electrons carry the
absorbed energy.
• Other molecular machinery use
the electrons to make ATP
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Photosynthesis Reactions
• Two main parts (reactions)
• Light Reaction or Light
Dependent Reaction produces
energy from sunlight to form
ATP & NADPH
• Dark Reaction or Light
Independent Reaction uses ATP
and NADPH to convert CO2 into
Glucose
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Light Reaction
• Occurs in the Thylakoid
membranes
• The light reaction uses light
energy to split water into
O2, H+, and e• O2 is released and the H+
and e- is used to produce
ATP and NADPH.
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Lets give Hydrogen a break!
• Hydrogen is the
smallest atom.
• It consists of a
single proton [+] and
a single electron [-].
• In photosynthesis
the H+ is carried by
NADP and the
electrons energy
goes to make ATP
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Light Dependent Reaction
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Dark Reaction
• Calvin Cycle or Light
Independent Reaction
• Uses energy (ATP and NADPH)
from light reaction to make
glucose
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Photosynthesis Overview
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Matter cycles as energy is transformed
P P P
Glucose
ATP
CHEMICAL
ENERGY
LIGHT
ENERGY
ENERGY
FOR CELLULAR
WORK
P P
Carbon dioxide
P
ADP + P
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Trace how the energy is transformed
Photosynthesis
Cellular respiration
P P P
Glucose
ATP
CHEMICAL
ENERGY
LIGHT
ENERGY
P P
P
Carbon dioxide
Light
energy
Photosynthesis
Energy stored
in glucose
Cellular respiration
Energy stored
in ATP
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