1. Chapter 8: Energy and Photosynthesis

2. Energy and Photosynthesis
Energy is necessary for all life
Plants and green organisms:
Trap light energy in the form of sunlight and store it for later use
All other organisms:
Eat green plants to obtain energy

3. Adenosine Triphosphate (ATP)
Energy molecule
Composed of:
Adenosine molecule
Ribose sugar
3 phosphate groups

4. ATP becomes available for a cell to use when the bonds between the phosphate groups are broken
Releases energy when a phosphate group is removed
Bond breaks between the 2nd and 3rd phosphate groups
Results in adenosine diphosphate (ADP)
ATP is a small molecule
Stored energy (ex: a battery)
Cells use energy to maintain homeostasis

5. Photosynthesis Photo-: means light Synthesis: to put together
Process that uses the sun’s energy to make simple sugars
2 phases
Light-dependent reactions
Light-independent reactions

6. History Van Helmont (1600’s) Priestley (1700’s) Ingenhous
Planted seedling in pot of soil, watering it regularly
Concluded plant mass comes from the water
Priestley (1700’s)
Candle with glass jar cover  flame died
Mint sprig and candle with glass jar cover  flame burned
Conclusion: plants release oxygen
Ingenhous
Supported Priestley  will occur only when mint plant is exposed to light

7. Photosynthesis Requirements
Light (sun)
Carbon Dioxide (from the air)
Taken in to plants through little openings in the leaves called stomata
Water (from the ground)
Taken in through the roots of plants
Chlorophyll and enzymes in the plant
Rate of photosynthesis depends on:
The availability of sunlight, CO2, and H2O
The intensity (brightness) of light
Temperature (20-35º C is optimal)

8. White light  mixture of different wavelengths of light
Visible spectrum  ROYGBIV
Pigments: molecules that absorb specific wavelengths of sunlight
Ex: Chlorophyll (in chloroplasts): a and b
Absorbs well in blue and red light
Absorbs most wavelengths except green (reflects green light)
Makes plants appear green
Other plant pigments:
Xanthophyll: yellow pigment
Carotene: orange pigment

9. Equation: 6CO2 + 6H2O + light  C6H12O6 + 6O2
Carbon Dioxide + Water  Sugar + Oxygen gas
Chloroplast: cell organelle where photosynthesis occurs
Light-dependent reactions take place in the thylakoid membrane (contains pigments)

10. Picture of a chloroplast:
Grana: stack of thylakoids
Stroma: outside of the thylakoids
Photosystem: clusters of pigment and protein that absorb light energy (found in thylakoids)

11. Review:
Match the scientist with the appropriate experiment or conclusion:
Priestley van Helmont Ingenhousz
_____ Plants need sunlight to produce oxygen
_____ Plants gain most of their mass by taking in water
_____ Using a candle and a jar, he observed that plants produce a substance that kept the candle burning
_____ He measured the mass of the soil in which a plant grew
_____ He observed plants exposed to light

12. Light-Dependent Reactions
1st phase
Requires light
Converts light energy into chemical energy
ATP produced fuels light-independent reactions
NADP+: electron carrier
Holds 2 high-energy electrons and H+
Converts NADP+ to NADPH

13. Occurs in the grana of chloroplasts Splits water (photolysis)
Light reactions use trapped light energy to convert ADP to ATP and NADPH
Occurs in the grana of chloroplasts
Splits water (photolysis)
H: needed to make glucose
O: released as a waste product into the atmosphere

14. Light ATP H+ (in grana) (in stroma) H2O in CO2 in C6H12O6 (glucose)
Light reactions
C6H12O6 (glucose)
Dark reactions H+
(in grana)
(in stroma)
H2O as waste
O2 as waste

15. Light-Independent Reactions
Does not require light
Called dark reactions or the Calvin cycle
Process of actually making glucose (uses CO2 to make simple sugars/starches)
Uses energy from ATP and NADPH
Can occur in the light or the dark
Requires enzymes
Occurs in the stroma of chloroplasts

16. Any glucose not used immediately can be stored as starch or sugars
Chemosynthesis
Process of making food from inorganic compounds
Does not use sunlight
Uses Sulfur in deep sea vents
Methanogens use Carbon Dioxide and Hydrogen

17. Autotrophs
Use photosynthesis or chemosynthesis
Make their own food

18. Bell Ringer:
The light-dependent reactions take place within the __________ membranes.
The light-independent reactions are also known as the ________.
In the light-dependent reactions, the gas ____ is produced.
High-energy sugars are produced during the _______ reactions.
The light-independent reactions take place in the ________.