1. Honors Biology: Photosynthesis

2. Important Root Words Root Word Meaning Photo Chloro -phyll Stome
Xantho
Light
Green
Leaf
Mouth
Yellow

3. Comprehension Check
How many characteristics of living things can you remember?
Which characteristic is related to this chapter?

4. All Organisms Need Energy
All organisms require energy to live. There are two main ways to obtain this necessary energy:
Cells use energy trapped in chemical bonds. When these bonds are broken, energy is released for cellular activities.
When cells use several linked chemical pathways to create the energy needed, this is called a biochemical pathway.
HETEROTROPHS
AUTOTROPHS

5. Cells use Energy
Cells find energy by breaking bonds in a very special molecule called . . .
ADENOSINE TRIPHOSPHATE (ATP)
ADP (adenosine diphosphate) is another important molecule involved with cellular energy

6. Storage and Release of Chemical Energy
Energy is stored (in a “high energy” bond) when a phosphate group is added to ADP
Energy is released from ATP when a phosphate group is removed (the “high energy” bond is broken)…
Note: This same system works between NADPH and NADP+

7. ATP: The Energy Currency

8. Visible Light Light travels as waves of energy
Reflection, Transmission, Absorption

10. Pigments in plants
Pigments: proteins that trap light energy from the sun, photosynthesis depends on this absorption of light to begin
Why do pigments appear as different colors?
EXAMPLES:
Chlorophyll : Appears green
A: Traps Red Light
B: Traps Blue Light
Accessory Pigments: Trap green/yellow
Carotene: Appears orange
Xanthophyll: Appears yellow
The least important color for photosynthesis?
GREEN!!

11. Chromatography
Can be used to separate plant pigments based on their molecular size
Watch a video!
Rf Values: Distance Pigment Moved (mm)
Distance Solvent Moved (mm)
NOTES:
Rf value will always be less than 1
The higher the Rf value, the smaller the pigment

12. Location of Photosynthesis
Chloroplasts
Thylakoid Membranes = photosynthetic sacs (site of light absorption)
Granum = stack of thylakoids
Stroma = liquid outside/surrounds the thylakoids

13. Comprehension Check
This weekend your teacher went to the store and bought a new, hi-tech, green colored plant growth light. She placed a plant underneath this light inside of the fume hood and closed it tightly.
Will the plant be able to undergo photosynthesis?

14. Overview of Photosynthesis
Definition: Process in which plants convert energy from the sun into stored chemical energy (glucose). 2 main reactions in photosynthesis: 1) Light Dependent Reaction 2) Light Independent (Dark) Reaction The General Reaction for Photosynthesis:
CO2 + H20  C6H12O6 + 02
(can you balance this equation?)
C H12 O6
CO H20 CO2
Temperature and Light Intensity can both affect the rate of photosynthesis, but it will either decrease or level off at some point.

15. 5 things needed for photosynthesis
Water
Sunlight
Carbon Dioxide
Chlorophyll (a light capturing pigment)
Enzymes

16. The Light-Dependent Reactions
Location: occurs in the thylakoid membranes
Function of First Stage:
Harvested light energy is converted from sunlight to electrical energy (ETC)
Uses energy from the sun to produce ATP and NADPH needed for next reaction
Important events you should know:
Chlorophyll is energized
Water is split
ATP and NADPH are formed
Hydrogen is trapped

17. The Light-Dependent Reactions
☼ (photons/light energy) ↓
Pigments in photosystem II and then photosystem I absorb energy
Electron Transport Chain
↓ ↓
Energy splits H ADP  ATP*
↓ ↓
O H trapped by NADP+
(forms NADPH *)
Energy used to form ATP from ADP
Both products here are used in the dark reaction

18. Electron Transport Chain
Process starts in a photosystem located on a thylakoid.
Absorption: Photosystem II absorbs energy from photons
Passage: electrons are passed to Photosystem I.
Transfer: electrons are transferred along the chain generating “electricity”.
Splitting: Electricity drives the splitting of water to form H+ and free oxygen.
Formation: Electrons provide energy for NADP+ to gain a H+ and form NADPH, also ATP is formed
ATP and NADPH are then used in the Dark Reaction/Calvin Cycle
Light Reaction Video

19. Calvin Cycle
Calvin Cycle (Dark/Light-Independent Reactions):
Location: takes place in the stroma Function: Uses energy from ATP and NADPH to produce high energy carbohydrates (sugars)
Does not require light to occur (can actually occur in light or dark)
Reactions form organic compounds using energy stored from Light-dependent reactions in bonds of NADPH and ATP
Named after American scientist, Melvin Calvin, who discovered this in the early 1950’s

20. The Calvin Cycle/Dark Reaction
These reactions can occur with or without Light!!
This begins and ends with RuBP = a 5-carbon sugar found in chloroplasts
CO2 + RuBP + ATP* (from Light Reaction) ↓
2(PGA) + 2H* (from Light Reaction)
 
2(PGAL) H20 (released as a waste product)
 
RuBP (80%) Glucose (20%)
Calvin Cycle Animation
CO2 given off

21. Calvin Cycle Diffusion: Carbon dioxide diffuses into the stroma
Combination: CO2 binds with 5-carbon molecule called RuBP. This forms an unstable 6-carbon molecule.
Splitting: This six carbon unstable molecule splits immediately into two molecules called PGA.
Conversion: PGA is changed into PGAL when:
A. PGA receives phosphate group from an ATP molecule from the light reaction
B. PGA accepts Hydrogen Ions from NADPH also from the light reaction
In summary, the Calvin Cycle fixes carbon dioxide and regenerates RuBP, produces PGA, then PGAL which may be converted to glucose.

22. Photosynthesis

23. Comprehension Check
Which parts of the process of photosynthesis can occur in the light?
Which parts of the process can occur in the dark?
How is the structure of the chloroplast related to its function?

24. Regulation of Photosynthesis
Stomata/Stoma: opening on underside of most leaves, entry site of carbon dioxide, release of oxygen from photosynthesis occurs here, water vapor is released here (transpiration)
Guard Cells: specialized cells that regulate opening and closing of stomata, open and close using a H+ pump and by manipulating the turgor pressure of the cells