1. Photosynthesis

2. Chemical Energy Where do you get your energy?
You eat food!
Carbohydrates and lipids have the most energy
This energy is only useable after it is broken down
Adenosine triphosphate (ATP) is a molecule that carries energy from the breakdown of food
When ATP is broken down to ADP (adenosine diphosphate), energy is released

3. Energy Sources Heterotrophs Autotrophs (producers)
Need to eat other organisms to gain energy
Autotrophs (producers)
Make their own food
Chemoautotrophs- use chemical energy to make food
Photoautotrophs- use energy from sunlight (through the process of photosynthesis)

4. Photosynthesis Overview
Photosynthesis: the process through which energy from sunlight is converted to chemical energy
Takes place in the chloroplasts
Two basic processes:
Light-dependent reactions capture energy from sunlight
Light-independent reactions use the energy captured in light-dependent reactions to make sugars
6 CO2 + 6 H2O C6H12O6 + O2
Carbon dioxide + water light, enzymes sugar oxygen

5. Chloroplast Grana: stacks of pancake-shaped thylakoid membranes
Stroma: fluid surrounding the grana
Chlorophyll: a molecule in the chloroplast that absorbs light energy
Chlorophyll a and chlorophyll b
Absorb mostly red and blue wavelengths of light; reflect green wavelengths
This is how plants get their color!

6. Light-Dependent Reactions
Energy is captured and transferred in the thylakoid membranes by two groups of molecules called photosystems
Energy is transferred to electrons
This is used to make energy-carrying molecules
ATP and NADPH

7. Photosystem II and Electron Transport
Energy absorbed from sunlight
Chlorophyll and other molecules absorb energy
Energy is transferred to electrons
High energy electrons enter the electron transport chain (series of proteins in thylakoid membrane)
Water molecules split
Oxygen, hydrogen ions (H+), and electrons separated
Oxygen is released as waste
H+ ions transported
Energy from electron transport chain is used to pump H+ ions from outside to inside the thylakoid membrane against a concentration gradient (active transport)
H+ ions build up inside thylakoid membrane
Electrons move on to photosystem I

8. Photosystem II

9. Photosystem I and Energy-Carrying Molecules
Energy is absorbed from sunlight and energizes electrons
NADPH (an energy molecule) is produced by electrons being added to NADP+ molecules
H+ ions diffuse through a protein channel called ATP synthase in the thylakoid membrane
Concentration is higher inside than outside (chemiosmotic gradient)
As H+ ions flow through ATP synthase, ATP is formed by phosphorylation of ADP molecules

10. Photosystems I and II

11. Summary of Light-Dependent Reactions
Energy is captured and transferred to electrons that enter the electron transport chain
Water molecules are broken down into oxygen, H+ ions, and electrons
Electrons provide energy for H+ ion transport and are added to NADP+ to form NADPH
H+ ions flowing through ATP synthase make ATP

12. Products of Light-Dependent Reactions
Oxygen is released as waste
Small amounts of NADPH and ATP

13. Light-Independent Reactions
Do not need sunlight
Uses energy from light-dependent reactions
Take place inside the stroma (fluid surrounding thylakoid membranes)
Also called the Calvin Cycle
Use carbon dioxide and ATP and NADPH molecules to build simple sugars

14. Calvin Cycle
Carbon dioxide is added to 5-carbon molecules inside the Calvin cycle to form 6-carbon molecules
Energy from light-dependent reactions is used to split 6-carbon molecules, forming two 3-carbon molecules
Out of every 3 CO2 molecules added to the Calvin cycle, one high-energy 3-carbon molecule exits
After two 3-carbon molecules have exited, they are bonded together to build a 6-carbon sugar
3-carbon molecules left in the cycle are changed back into 5-carbon molecules using ATP

15. Calvin Cycle Summary Calvin cycle turns 6 times
Produces 6-carbon simple sugars
Typically glucose molecules
Most important enzyme: ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO)
Most abundant enzyme on earth

17. Photosynthesis

18. Photosynthesis Summary
Light-dependent reactions
Photosystem II
Energy captured and transferred to electrons
Water molecules split, releasing oxygen
H+ ions build up inside thylakoid
Photosystem I
Energy absorbed, energizing electrons
NADPH produced
ATP produced by flow of H+ ions through ATP synthase
Light-independent reactions
Calvin cycle
CO2 is broken down and ATP and NADPH is used to build 6-carbon sugar
Uses the enzyme RuBisCO