2. Photosynthesis: Life from Light and Air

3. Energy needs of life All life needs a constant input of energy
Animals = Heterotrophs
get their energy from “eating others”
eat food = other organisms = organic molecules
make energy through respiration
Plants = Autotrophs
get their energy from “self”
get their energy from sunlight
build organic molecules (food) from CO2
make energy through photosynthesis

4. Carbon Dioxide + Water → Glucose + Oxygen
Photosynthesis: the process that uses the sun’s energy to make simple sugars, such as glucose.
6CO2 + 6H2O → C6H12O6 + 6O2
Carbon Dioxide + Water → Glucose + Oxygen
What are some sources of carbon dioxide for plants? Natural sources of atmospheric carbon dioxide include volcanic outgassing, the combustion of organic matter, and the respiration processes of living aerobic organisms; man-made sources of carbon dioxide include the burning of fossil fuels for heating, power generation and transport, as well as some industrial processes such as cement making. It is also produced by various microorganisms from fermentation and cellular respiration
What are some sources of water for plants?

5. How do plants live? Photosynthesis Energy building reactions
collect sun energy
make ATP
Sugar building reactions
use ATP for energy
use CO2 as carbon for new sugars
build sugars
glucose, cellulose, starch
build all other organic molecules
proteins, lipids, carbohydrates, DNA
store energy for future use
starch in seeds & roots

6. Energy building reactions Sugar building reactions
Photosynthesis
Energy building reactions
Sugar building reactions
sun
ATP
ADP
CO2
sugar
Actually 2 separate reactions
Energy building
use sunlight
make energy (ATP)
Sugar building
use ATP
use CO2
make sugars (C6H12O6)

7. Chloroplasts absorb sunlight & CO2 make energy & sugar
Contain chlorophyll

8. Light-Dependent Reactions
H2O +
light
energy 
ATP + O2
H2O
makes ATP energy
releases oxygen as a waste product
sunlight
Energy Building
Reactions
ATP O2

9. Light-Independent Reactions
sugars
C6H12O6
CO2
Sugar Building
Reactions
ATP
ADP
CO2 + 
ATP
C6H12O6 +
ADP
builds sugars
uses ATP
cycles ADP back to make more ATP
The first phase of photosynthesis requires light and is known as light-dependent reactions. Sunlight comes in and hits the chlorophyll the energy of light is transferred to electrons that are passed along the electron transport chain – which is a series of proteins embedded in the thylakoid membrane.
The second phase of photosynthesis does not require light and is called many things including light-independent reactions, the dark reactions and the calvin cycle. These reactions take CO2 and the energy from the light reactions – in the form o fATP and NADPH – and produces sugar and oxygen.

10. Putting it all together
CO2
H2O
C6H12O6 O2
light
energy  +
H2O
Plants make both:
ATP
sugars
CO2
sunlight
ADP
Energy Building
Reactions
Sugar Building
Reactions
ATP
sugars
C6H12O6 O2

11. So what does a plant need?
Bring In
CO2
H2O
light
Let Out O2
Move Around
sugars
leaves
shoot
roots
6CO2
6H2O
C6H12O6
6O2
light
energy  +