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This presentation gives a brief introduction to photosynthesis. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities.
1.
4.2 Overview of Photosynthesis
KEY CONCEPT
The overall process of photosynthesis produces
sugars that store chemical energy.
2.
4.2 Overview of Photosynthesis
Photosynthetic organisms are producers.
• Producers make their own
source of chemical energy.
• Plants use photosynthesis and
are producers.
• Photosynthesis captures
energy from sunlight to make
sugars.
3.
4.2 Overview of Photosynthesis
• Chlorophyll is a molecule
that absorbs light energy. chloroplast
• Chlorophylls primarily absorb
red and blue light and reflect
green.
• In plants, chlorophyll is
leaf cell
found in organelles called
chloroplasts.
leaf
4.
4.2 Overview of Photosynthesis
Photosynthesis in plants occurs in chloroplasts.
• Photosynthesis takes place in two parts of chloroplasts.
– grana (thylakoids)
– stroma grana (thylakoids)
chloroplast
stroma
5.
4.2 Overview of Photosynthesis
• The light-dependent reactions capture energy from
sunlight.
– take place in thylakoids
– water and sunlight are needed
– chlorophyll absorbs energy
– energy is transferred to light-independent reactions
– oxygen is released from the splitting of water
6.
4.2 Overview of Photosynthesis
• The light-independent reactions make sugars.
– take place in stroma
– needs carbon dioxide from atmosphere
– use energy to build a sugar (usually glucose) in a cycle
of chemical reactions
7.
4.2 Overview of Photosynthesis
• The equation for the overall process is:
6CO2 + 6H2O C6H12O6 + 6O2
granum (stack of thylakoids)
1s chloroplast
chloroplast
un
lig
ht
6H2O 6O2
2
energy
thylakoid
stroma (fluid outside the thylakoids)
6CO2 1 six-carbon sugar
C6H12O6
3 4
8.
4.2 Overview of Photosynthesis
9.
4.2 Overview of Photosynthesis
10.
4.2 Overview of Photosynthesis
Exercises
• What are the roles of chloroplasts and chlorophyll in
photosynthesis?
• Describe the stages of photosynthesis. Use the terms
thylakoid, light dependent, and light independent
reactions in your answers.
• Suppose you wanted to develop a light to increase plant
growth. What characteristics should the light have?
Why?
• Explain why photosynthesis is important for building the
structure of plant cells.
• Overall, do you think photosynthesis is exothermic or
endothermic? Explain your answer.
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