4.1 Photosynthesis
7.1.d Students know that mitochondria
liberate energy for the work that cells do
and that chloroplasts capture sunlight
energy for photosynthesis.
Sources of Energy
• ALL cells need energy!
• Photosynthesis- process by
which a cell captures energy in
sunlight and uses it to make
food
• Key Concept: “Nearly all living
things obtain energy either
directly or indirectly from the
energy of sunlight captured
during photosynthesis."
• Autotroph- organism that
makes its own food
• Heterotroph- organism that
cannot make its own food
Sources of Energy
The Two Stages of Photosynthesis
Stage 2
The captured light
energy is used to
produce sugars and
oxygen from water and
carbon dioxide.
Carbon dioxide enters the
leaf through openings
called stomata
Water inters the plant
through roots and moves
upward to the leaves
Key Concept: “During photosynthesis, plants
and some other organisms use energy from
the sun to convert carbon dioxide and water
into oxygen and sugars.”
Sugar
produced
are used
by the
plant cells
for energy
Oxygen exits
through the
stomata on the
underside of
the leaf.
The Two Stages of Photosynthesis
• Photosynthesis takes place in 2 stages: capturing
sunlight and producing sugar
• Pigments- colored chemical compounds that absorb
light
• Chlorophyll- main photosynthetic pigment in
chloroplasts
• Chloroplasts- are the green organelles in plant cells
that give the plant its color
• Chlorophyll is like solar “cells” or cells that capture the
energy in light in a calculator
• The captured light is used to power the second stage
The Two Stages of Photosynthesis
• 2 raw materials needed for stage 2 are water and carbon
dioxide
• Roots absorb water, water then moves up through stem to the
leaves, carbon dioxide enters through the stomata
• Once the water and carbon dioxide are in the leaf they move
into the chloroplasts
• Stomata- small openings on the underside of leaves
• In the chloroplasts the water and carbon dioxide go through
chemical reactions
• These chemical reactions are powered by the energy
captured in stage 1
• One important byproduct of this chemical reaction in oxygen
and exits through the stomata
The Two Stages of Photosynthesis
• The Photosynthesis equation:
Sugar
Light energy
Oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
Carbon Dioxide
Water
The Photosynthesis Process Activity
• Click the Active Art button to open a browser window
and access Active Art about the photosynthesis
process.
Review
How does the sun supply living
things with the energy they
need?
What happens during the
process of photosynthesis?