photosynthesis notes
TRANSCRIPT
Autotrophs vs. Heterotrophs
Autotroph
Make their own
food
Example: Plants
Heterotroph
Obtain energy from
foods they eat
Example: Animals,
fungi
Autotrophs
Photosynthesis occurs within:
Some bacteria
Algae
Within leaves of plants
does NOT happen in ALL cells
Chemical EnergyEnergy – the ability to do work
Adenosine Triphosphate (ATP)
Adenine
Ribose
3 phosphate groups
ADP + P
Adenosine diphosphate + phosphate
Light and PigmentPlants gather the Sun’s energy
with light absorbing molecules
called pigments
Chlorophyll (Green)
chlorophyll a and chlorophyll b
Light-Dependent ReactionsLocation: Thylakoid Membrane
1. Photosystem II
Light energy absorbed by electrons and increases their energy level
Enzymes break up water molecules into: 2 electrons
2 hydrogen ions
1 oxygen atom
2. Electron Transport Chain
High-energy electrons move
hydrogen ions from the stroma
into the inner thylakoid space
Light-Dependent ReactionsLocation: Thylakoid Membrane
3. Photosystem I
Uses energy from light to re-energize the electrons.
NADP+ picks up electron and 2 H+
ions
Produces NADPH
Light-Dependent ReactionsLocation: Thylakoid Membrane
4. Hydrogen Ion Movement
Hydrogen ions move
across the thylakoid
membrane making the
inside positively charged
Light-Dependent ReactionsLocation: Thylakoid Membrane
5. ATP Formation
Hydrogen ions pass through ATP
synthase (protein)
Energy is converted from ADP
to ATP
Light-Dependent ReactionsLocation: Moves from Thylakoid to Stroma
Calvin CycleLocation: Stroma
1. Carbon Fixation
6 CO2 combines with a
five-carbon sugar
Enzyme breaks down to
12 three-carbon molecules
2. Energy Input
ATP is broken down giving each
three-carbon molecule a
phosphate
NADPH gives up electrons to
provide more energy
Calvin CycleLocation: Stroma
3. Sugar Production
2 three-carbon molecules exit
cycle to be used by the plant
10 three-carbon molecules are
recycled
Calvin CycleLocation: Stroma
4.5-Carbon Molecule Regeneration
10 three-carbon molecules are converted back into 6 5-carbon molecules to be used in the next cycle
6 ATP molecules are used to complete this process
Calvin CycleLocation: Stroma
Factors Affecting Photosynthesis
Water
Plants in dry conditions have a waxy coating on the leaves that reduce water loss
Temperature
Photosynthesis depend on enzymes that function best between 0oC and 35oC
Light Intensity
Increasing light intensity increases the rate of photosynthesis
However, a plant has a maximum rate of photosynthesis that can be reached