Photosynthesis
Ancient Earth – Before
Photosynthesis
Today – Lush with Autotrophs
Thanks Plants!
• Up to 85% of the Oxygen on
Earth comes from
photosynthetic autotrophs!
• Plants filter the air and reduce
atmospheric pollutants!
• Shown: Vertical garden in Paris
Photosynthesis
• Autotrophs internally create sugar (food)
through absorbing water, carbon dioxide,
and radiant energy from the sun
• Photo = light
• Synthesis = to make
Simple Sugar Uses
• Glucose – provides immediate energy for
the plant
• Starch – polysaccharide used for energy
storage
• Cellulose – polysaccharide used to
strengthen cell wall
Photosynthetic Organisms
Pigment in green plants
• Chlorophyll – pigment that reflects green
light but absorbs blue and red light
Other pigments
Plant Cell
The chloroplast
• Sites of photosynthesis
• Double membrane
• Pigment: chlorophyll
(located in the thylakoid)
• Light dependent
reactions occur in the
thylakoid
• Light independent
reactions occur in the
stroma
Chloroplasts
Microscope View
Photosynthesis: an overview
• The light-dependent reactions
convert light energy into
chemical energy (ATP).
• The molecules of ATP
produced in the lightdependent reactions are then
used to fuel the lightindependent reactions that
produce simple sugars.
• 6CO2 + 6H2O → C6H12O6 +
6O2
What is ATP???
● ATP= ENERGY
● Adenosine Triphosphate or ATP is an
energy molecule that provides direct
energy to your cells
● ATP is composed of an adenosine
molecule with 3 phosphate groups attached
When the bond breaks, energy is
released
What is ADP???
● When one phosphate group breaks away,
ATP becomes Adenosine Diphosphate
(ADP)
● ADP has only two phosphate groups and
holds less energy than ATP
● ATP
ADP
ATP
Factors that affect the rate of
photosynthesis:
• Limiting factors
Light Dependent Reactions
• Located in the thylakoid
membrane
• Pigment molecules are
struck by light and give off
an electron
• Electron transport produces
ATP
• e- is replaced by splitting
water (releases O2)
Light Independent Reactions
•
•
•
Also called the Calvin
Cycle
Occurs in the stroma of
the chloroplast
6 molecules of CO2 are
converted into glucose
How Autotrophs Use Intermediates and Products of
Photosynthesis
• What do they do with the sugar??
• Glucose is used as cellular fuel and as building
blocks in synthesis of carbohydrates
• Sucrose is transported from leaves to all parts of
the plant
• Starch is the main storage form of carbohydrate in
plants
• Cellulose is used to make plant cell walls
A review of photosynthesis