1. Chapter 8
Photosynthesis

2. History
• Jan Van Helmont (1643) – discovered that
plants must get their food from H2O
• Joseph Priestley (1771) – plants produce
02
• Jan Ingenhousz (1779) – light was
necessary for plants to produce 0 2

3. • Energy – the ability to do work
• Autotrophs – organisms such as plants
can make their own food.
• Heterotrophs – obtain food from other
organisms

4. Chemical Energy
• Living things use chemical energy as fuel
• Adenosine triphosphate (ATP) – principal
compound that cells use to store and
release energy
• Composed of
• Adenine – ribose – 3 phosphate group
• By adding a phosphate to ADP- ATP
snythase - (has 2) (poor energy storer)
ATP is created

5. Releasing energy
• By breaking the bond between the 2 nd and
3rd phosphate, energy is released
• Characteristics of ATP make it an
exceptional source of energy of all cells
• Powers protein synthesis and nucleic
acids, active transport (energy required)
• Cells contain small amounts of ATP (about
90 sec)

6. Photosynthesis
Light
• 6CO2 + 6H2O → C6H12O6 + 6O2
Light
• Carbon Dioxide + Water → Glucose + oxygen
• Uses energy of light to convert carbon
dioxide and water into high energy sugars
and oxygen

8. Structures of Photosynthesis
• Pigments – light absorbing molecules
• Chlorophyll – principal pigment in plants
• light is a form of energy that is found in the
visible spectrum
• Plants absorb light, therefore, they absorb
energy in the form of electrons which
allows photosynthesis to take place
• Plants can use all of the visible spectrum
except green

9. Cont.
• Chloroplast – structure where photosynthesis
takes place
• Thylakoids – saclike photosynthetic membranes
arranged into stacks called granum
• Photosystem – light collecting units of the
chloroplast
• Stroma – region outside thylakoid membrane
where the Calvin cycle takes place

10. Light dependent reaction
• Takes place within the granum (stacked
thylakoids)
• Light is required
• Reaction produces oxygen and converts
ADP and NADP+ into the energy carriers
ATP and NADPH (used in Calvin Cycle)
• These are required to build energy
containing sugars from low energy
compounds

12. Light independent reaction
• Calvin cycle – uses ATP and NADPH from the
light dependent reaction to produce high energy
sugars
• Takes place in the stroma
• Uses 6 CO2 molecules to produce 6 sugar
molecules (high energy)

14. Factors
• Temperature
• Light intensity
• Water

15. Summary
• Two sets of photosynthetic reactions work
together:
• Light dependent reactions trap the
energy from sunlight in chemical form and
the light independent reaction (Calvin
Cycle) uses that energy to produce stable
high energy sugars from water and CO 2
creating O2