CH-8 Photosynthesis - Newark City Schools

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How do organisms get energy?
• Autotrophs and Heterotrophs
–Autotrophs – organisms that
can capture energy from
sunlight or chemicals and use
it to produce its own food.
How do organisms get energy?
• Autotrophs and Heterotrophs
–Heterotrophs – organism that
obtains energy from the
foods it consumes
Chemical Energy and ATP
 ATP (adenosine triphosphate) = The
principal chemical compound that
living things use to store energy
o ATP = 3 Phosphate groups
 ADP (adenosine diphosphate) has a very
similar structure to ATP, but with only two
phosphate groups.
o ADP = 2 Phosphate groups
Chemical Energy and ATP
• The energy stored in ATP is released
when ATP is converted to ADP. The
breaking of the bond between the
second and third phosphate group
releases this energy.
Chemical Energy and ATP
ATP
ADP
Fully
charged
battery
Partially
charged
battery
Investigating Photosynthesis
• When a tiny seedling grown into a tall tree
with a mass of several tons, where does
the tree’s increase in mass come from?
From soil? From water? From air?
Investigating Photosynthesis
 Van Helmont – 1600s
o Wanted to know if plants grew by taking
material out of the soil.
o Weighed a pot of dry soil and a small
seedling. He watered it regularly and at the
end of five years the seedling had gained 75
kg. The mass of the soil was exactly the
same.
o Helmont concluded that the mass gain came
from water
o HE WAS WRONG
Investigating Photosynthesis
 Priestly – 1700s
oPut a candle under a bell jar, the
fire went out. Added a small plant
and the fire continued to burn for a
few days.
Through the work of all these scientists it was discovered that…..
• In the presence of light, plants
transform carbon dioxide and
water into carbohydrates and
release oxygen
Investigating Photosynthesis
 Ingenhousz
o Showed that Priestly’s results were only valid
if the plant was exposed to light.
Photosynthesis
 6CO2 + 12H2O + light → C6H12O6 + 6O2
 Photosynthesis uses the energy of
sunlight to convert water and carbon
dioxide into oxygen and high-energy
sugars
Light and Pigments
 Plants gather the sun’s energy with lightabsorbing molecules called pigments.
 The plant’s principal pigment is
chlorophyll
Inside a Chloroplast
 Photosynthesis takes place inside
the chloroplast
oChloroplasts contain saclike
membranes called thylakoids (looks
like a pancake)
oA stack of thylakoids is known as
grana (looks like a stack of pancakes)
oThe area outside of the grana, but
inside the chloroplast is known as
stroma (kind of like the syrup on the
pancakes)
Inside a Chloroplast
The Chemical Reactions of
Photosynthesis
• NADPH
 Like ATP, the molecule
NADPH can also store
energy.
o NADP+ + Energy  NADPH
o So when an organism
breaks down NADPH energy
it gets NADP+ and energy
NADPH
NADP+
Fully
charged
battery
Partially
charged
battery
The Chemical Reactions of
Photosynthesis
• Light-Dependent
Reactions
 REQUIRE LIGHT
 Light-dependent reactions
produce oxygen gas and
convert ADP and NADP+
into the energy carriers ATP
and NADPH
 Harvests the sun’s energy
and charges the battery
The Chemical Reactions of
Photosynthesis
• Calvin Cycle
 Because the Calvin Cycle does not require
light, it is also called light-independent
reactions
 The Calvin cycle uses ATP and NADPH
form the light-dependent reactions to
produce sugar
Uses the energy stored in
the light-dependent
reactions to create food.
Factors Affecting Photosynthesis
 Weather
oAmount of rain
oTemperature
oIntensity of light
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