1. Photosynthesis
The Flow of Energy

2. ATP adenosine triphosphate
chemical compound used by living things to store energy
When the bond between two phosphate groups is broken – energy is released
ATP  ADP + Pi

3. Photosynthesis Jan van Helmont – plants gain their mass from water
Joseph Priestly – plants release oxygen
Jan Ingenhousz – light is necessary for plants to produce oxygen
6CO2 + 6H2O  C6H12O6 + 6O2

4. Light Visible spectrum – ROYGBIV Red = longest wavelength
Violet = shortest
wavelength
Color of an object
is determined by
the color the object reflects
Plants gather light using pigments

5. Chloroplasts and Pigments
chloroplast – organelle where photosynthesis occurs
chlorophyll – a green pigment, most important in photosynthesis
carotenoids – yellow, orange and red pigments
absorbed light is transformed from light energy to chemical energy

6. Inside a Chloroplast thylakoids – saclike photosynthetic membranes
grana – stacks of thylakoids
stroma – space outside the thylakoids

7. Overview of Photosynthesis
photosynthesis occurs only in producers
endergonic reaction – a chemical reaction that uses or stores energy
Two steps of photosynthesis
Light Reactions
Calvin Cycle

8. Light Reactions require light
use energy from light to produce ATP and NADPH
occurs in the grana
energy from “excited electrons” is used to bond ADP and Pi to form ATP

9. Light Reactions 3 main events
Light energy is absorbed by the chlorophyll and ATP is made
Water is split into hydrogen ions, oxygen and electrons
The hydrogen ions are used to make NADPH

10. Light Reactions
Inputs:
Light
Water
Outputs:
ATP
NADPH
Oxygen (O2)

11. Calvin Cycle
Also called the dark reactions or light-independent reactions
process of synthesizing sugars
occurs in the stroma
does not require light
converts CO2 to sugar

12. Calvin Cycle 3-carbon sugars are produced Some used as energy sources
Some converted to lipids, amino acids, parts of nucleic acids
Two can combine to form 6-carbon sugars

13. Calvin Cycle
Inputs:
ATP
NADPH
CO2
Outputs:
Sugars

14. In the end…
a single 6-carbon sugar is formed from 6 molecules of carbon dioxide
plants use the sugar for energy and to build more complex carbohydrates such as starches and cellulose
other organisms eat the plants and use the energy stored in carbohydrates

15. Factors Affecting Photosynthesis
Shortage of water
Can slow or stop photosynthesis
Temperature
Photosynthesis requires enzymes that function best between 0°C and 35°C
Intensity of light
Increasing light intensity increases the rate of photosynthesis