4.2 Overview of Photosynthesis
Season 3: Respiration, Photosynthesis,
and Fermentation
Episode 1: Function of the Chloroplast
Objective: Describe the chloroplasts' role in
photosynthesis and what is produced.
4.2 Overview of Photosynthesis
KEY CONCEPT
The overall process of photosynthesis produces
sugars that store chemical energy.
4.2 Overview of Photosynthesis
Gamma
raysX-rays UV Infrared
Micro-
waves
Radio
waves
Visible light
Wavelength (nm)
Why are plants green?
• Different wavelengths of visible light are seen by the
human eye as different colors
4.2 Overview of Photosynthesis
• Pigments absorb
certain wavelengths
of light and reflect
others.
4.2 Overview of Photosynthesis
• What color of light do
green plants use for
photosynthesis???
4.2 Overview of Photosynthesis
• Plant cells contain
the photosynthetic
pigment chlorophyll
• Found in chloroplasts
4.2 Overview of Photosynthesis
The chemical energy used for most cell processes is
carried by ATP.
• Molecules in food store chemical energy in their bonds.
• Photosynthesis creates sugars that is later used to
make ATP.
Starch molecule
Glucose molecule
4.2 Overview of Photosynthesis
Photosynthesis occurs in the chloroplast.
• The chloroplast is made of
two parts.
– Thylakoids: Like
stacks of pancakes
– Stroma: the syrup you
put on those yummy
pancakes
chloroplast
stroma
grana (thylakoids)
4.2 Overview of Photosynthesis
• The light-dependent reactions capture sunlight.
– Uses water and sunlight, creates ATP
– Occurs in the thylakoid membrane
Photosynthesis has two main steps.
4.2 Overview of Photosynthesis
• The light-independent (Calvin cycle) reactions make
sugars.
– Uses carbon dioxide and ATP, creates glucose
– Occurs in the stroma
4.2 Overview of Photosynthesis
• The equation for the overall process is:
6CO2 + 6H2O C6H12O6 + 6O2
C6H12O6
granum (stack of thylakoids)
thylakoid
1 six-carbon sugar
6H2O
6CO2
6O2
chloroplast1
2
43
energy
stroma (fluid outside the thylakoids)
4.2 Overview of Photosynthesis
4.2 Overview of Photosynthesis
• Pg. 104
• Fill in the blanks
• Color and give a written description of photosynthesis and
function of chloroplast
• 15 min.
4.2 Overview of Photosynthesis
• Draw two circles
• Make a wet mount with elodea leaf
• Start with low power, focus and then move to medium and
high. Draw a picture for each.
• Label and include magnification
4.2 Overview of Photosynthesis
• Around how many chloroplasts were in one leaf cell?
Now estimate around how many leaf cells were in the
entire leaf you observed, keeping in mind that the leaf is
three cell layers thick. Based on these two estimations,
predict how many chloroplasts would be in the picture of
the elodea plant that is on the front of this page. SHOW
ALL YOUR MATH!
• Chloroplasts are responsible for harvesting light energy
and transferring this energy to a usable form: sugar.
Consider your estimation of the number of chloroplasts in
the elodea plant. In relative terms, what does your
estimation tell you about the amount of energy a single
chloroplast can make? (Do you think it makes a lot of
energy?) Explain why plants have so many leaves