Photosynthesis
LN #15
California State Standards for Cell Biology
1f. usable energy is captured from sunlight by chloroplasts and is stored
through the synthesis of sugar from carbon dioxide.
Overview of Photosynthesis
Purpose of photosynthesis is to turn light energy into chemical energy.
Chemical energy is stored in glucose.
glucose C6H12O6
CO2
H 2O
O2
6 CO2 + 6 H2O
Light energy
C6H12O6 + 6 O2
Where does Photosynthesis take place?
• Photosynthesis takes
place in the leaves of
plants.
• Chloroplast is the
organelle responsible
for carrying out
photosynthesis.
– In the figure circle the
chloroplast.
Leaf and Chloroplast Structure
Leaf and Chloroplast Structure
• Leaf structure
– Stomata = tiny pores in the leaf, carbon dioxide enters and
oxygen exits.
• Inside the chloroplast
– stroma = thick fluid enclosed in the inner membrane of the
chloroplast. The stroma is where glucose is made from
carbon dioxide.
– thylakoids = disk like sacs within the stroma. Thylakoids
are connected in stacks called grana. Chlorophyll
molecules are built into the thylakoid membrane.
• chlorophyll molecules are a pigment that capture light energy.
Photosynthesis Occurs In Two Parts
Part One: The Light Reactions
• Light energy is changed into chemical energy.
– Oxygen gas is a waste product of this reaction.
• The light reactions happen in the thylakoid
membrane of the chloroplast.
• Light energy is caught by the chlorophyll and
used to make ATP from ADP and phosphate.
• Light energy is also stored in a molecule called
NADPH.
Part Two: The Calvin Cycle
• During the Calvin cycle sugar is made using
carbon dioxide and the energy storing
molecules (ATP and NADPH) made during the
light reactions.
• Calvin cycle takes place in the stroma of the
chloroplast.
Summary
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What is photosynthesis?
Where does photosynthesis take place?
How many parts does photosynthesis have?
What occurs during the light reactions?
What occurs during the Calvin cycle?