2. Contents
What is photosynthesis?
Overview
Where does photosynthesis occur?(Leaf)
Structure of leaf
Why do plants need photosynthesis?
Requirements
Photosynthesis: the chemical process
Benefits of photosynthesis
3. What is photosynthesis?
The biochemical process in which
sun light fixes carbon dioxide into
glucose in the
presence of water is
called photosynthesis.
4. Photosynthesis in Overview
• Process by which plants and other autotrophs store
the energy of sunlight into sugars.
• Requires sunlight, water, and carbon dioxide.
• Overall equation:
6 CO2 + 6 H20 + sunlight C6H12O6 + 6 O2
• Occurs in the leaves of plants in organelles called
chloroplasts.
6. Leaf Structure
• Most photosynthesis occurs in the palisade layer.
• Gas exchange of CO2 and O2 occurs at openings called
stomata surrounded by guard cells on the lower leaf
surface.
Palisade
Spongy
7. Chloroplast Structure
• Inner membrane
called the thylakoid
membrane.
• Thickened regions
called thylakoids. A
stack of thylakoids is
called a granum.
(Plural – grana)
• Stroma is a liquid
surrounding the
thylakoids.
8. Pigments
• Chlorophyll A is the most important
photosynthetic pigment.
• Other pigments called antenna or accessory
pigments are also present in the leaf.
– Chlorophyll B
– Carotenoids (orange / red)
– Xanthophylls (yellow / brown)
• These pigments are embedded in the membranes
of the chloroplast in groups called photosystems.
9.
10. Why do plants need
photosynthesis?
• Glucose is the food for the plant. It gives
the plant energy to grow.
• They do photosynthesis to gain energy.
12. Photosynthesis: The Chemical Process
• Photosynthesis is a chemical process.
• It occurs in two main phases.
– Light reactions
– Dark reactions (the Calvin Cycle)
13. Light Reactions
• Light-dependent reactions occur on the thylakoid
membranes.
– Light and water are required for this process.
– Light reactions are the “photo” part of
photosynthesis.
– Light is absorbed by pigments and is
transformed into ATP and NADPH molecules
14. Dark Reactions
• Dark reactions (light-independent) occur in the
stroma.
– Dark reactions are the synthesis parts of
photosynthesis
– Trapped energy by pigments is converted into
chemical ennergy
– Carbon dioxide is “fixed” into glucose
– ATP and NADPH molecules created during the
reaction is responsible for production of this
glucose
16. How much glucose does a plant
make?
• Plants make enough glucose to be used
during the night and on cloudy days when
they don’t get sunlight
• The extra glucose is stored in the
plant’s leaves and other parts.
17. Advantages
Basic source of energy for all livings
Production of oxygen
Healthy environment
Lessen global warming
