1. PHOTOSYNTHESIS

2. Photosynthesis 6CO2 + 6H2O  C6H12O6 + 6O2 SUN photons glucose
Photosynthesis is a(n) Anabolic because it combines simple molecules into more complex molecules.
Photosyntheis is an Endergonic (stores energy)
Energy from the sun is stored in the bonds of the sugar glucose
Carbon dioxide (CO2) serves as a carbon source for photosynthesis.
Sunlight is absorbed as packets of energy called photons.
Besides Carbon dioxide (CO2), light energy (photons) and water (H2O) is also used in photosynthesis to produce organic macromolecules (glucose).
6CO H2O  C6H12O O2
sunlight
glucose
SUN
photons

3. Where does photosynthesis take place?
Question:
Where does photosynthesis take place?

4. Plants Autotrophs – produce their own food (glucose)
Process called photosynthesis
Mainly occurs in the leaves:
a. stoma – pores underside
b. mesophyll cells—contain
chlorophyll
c. In mesophyll cells-chlorophyll is
in the organelle chloroplast
Mesophyll
Cell
Chloroplast
Stoma

5. Stomata (stoma)
Pores in a plant’s cuticle through which gases (CO2 & O2) and water vapor are exchanged between the plant and the atmosphere.
Guard Cell
Oxygen
(O2)
Stoma
Carbon Dioxide
(CO2)
Found on the underside of leaves

6. Mesophyll Cell of Leaf Photosynthesis occurs in these cells! Nucleus
Cell Wall
Chloroplast
Central Vacuole
Photosynthesis occurs in these cells!

7. Chloroplast Thylakoid stacks are connected together Stroma
Organelle where photosynthesis takes place.
Outer membrane allows materials to pass through to inside the chloroplast
Stroma is the thick fluid inside the chloroplast
Granum are stacks of thylakoids attached to each other in the inner membrane of a chloroplast
Stroma
Outer Membrane
Thylakoid
Granum
Inner Membrane
Thylakoid stacks are connected together

8. Grana make up the inner membrane
Thylakoid
Thylakoid Membrane
Granum
Thylakoid Space
Grana make up the inner membrane

9. Question:
Why are plants green?

10. Chlorophyll Molecules
Plants are green because the green wavelength is reflected, not absorbed.
Located in the thylakoid membranes
Chlorophyll pigments harvest light energy (photons) by absorbing certain
Chlorophyll have Mg+ in the center
wavelengths (blue-420 nm and red-660 nm are most important)

12. Wavelength of Light (nm)
400
500
600
700
Short wave
Long wave
(more energy)
(less energy)

13. Absorption of Light by Chlorophyll
Chlorophyll absorbs blue-violet & red light best
violet blue green yellow orange red
Absorption
wavelength

14. During the fall, what causes the leaves to change colors?
Question:
During the fall, what causes the leaves to change colors?

15. Fall Colors
In addition to the chlorophyll pigments, there are other pigments present
During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments
Carotenoids are pigments that are either red, orange, or yellow

16. Why do leaves turn Colors in the Fall?
Number 27:
Due to the earth’s tilt on its axis, in the fall:
1.The sunlight has indirect rays and thus less energy to be absorbed by the plants. Plants are reflecting different colors than green.
2. The amount of sunlight is less each day = less photosynthesis

17. Chemical Equation of photosynthesis
sunlight
glucose
6CO H2O  C6H12O O2
Carbon dioxide
Oxygen
Water

18. What do cells use for energy?
Question:
What do cells use for energy?

19. Energy for Life on Earth
Sunlight is the ULTIMATE energy for all life on Earth
Plants store energy in the chemical bonds of sugars
Chemical energy is released during cellular respiration as ATP

20. Structure of ATP ATP stands for adenosine triphosphate
It is composed of the
1. nitrogen base ADENINE,
2.the pentose (5C) sugar RIBOSE, PHOSPHATE groups
The LAST phosphate group is bonded with a HIGH ENERGY chemical bond
This bond can be BROKEN to release ENERGY for CELLS to use

21. Removing a Phosphate from ATP
Breaking the LAST PHOSPHATE bond from ATP, will ---
1. Release ENERGY for cells to use
2. Form ADP
3. Produce a FREE PHOSPHATE GROUP

22. High Energy Phosphate Bond

23. FREE PHOSPHATE can be re-attached to ADP reforming ATP
Process called Phosphorylation

24. Phosphorylation

25. Number 38:
Energy released from this is available for cellular work.

26. Parts of Photosynthesis

27. Two Parts of Photosynthesis
Two reactions make up photosynthesis:
1.Light Reaction or Light Dependent Reaction -
Produces energy from solar power (photons) to produce ATP and the energy carrier NADPH.
SUN

28. Two Parts of Photosynthesis
2. Calvin Cycle or Light Independent Reaction (Dark Reactions).
Uses energy (ATP and NADPH) from light reaction to make sugar (glucose)—not directly from the sun.
Also called Carbon Fixation or C3 pathway

29. Light Reaction (Electron Flow)
Occurs in the Thylakoid membranes
During the light reaction, there are two possible routes for electron flow:
A. Cyclic Electron Flow
B. Non-cyclic Electron Flow

30. Cyclic Electron Flow Occurs in the thylakoid membrane.
Uses Photosystem I only
P700 reaction center- chlorophyll a
Uses Electron Transport Chain (ETC) and ATP Synthase
Generates ATP only
ADP ATP P

32. Noncyclic Electron FlowP
ADP +  ATP
NADP+ + H  NADPH
Oxygen made by plants comes from the splitting of H2O (number 47), not CO2
H2O  /2 O2 + 2H+

34. Number 46:
Water is split in Noncyclic, while NADPH is made in Electron Transport chain (ETC) (from previous slide).

35. Number 48:
Electron Transport Chain (ETC) powers ATP Synthesis in plants. (see illustration on next slide).
Number 49:
ATP is made using the electron transport chain and the enzyme NADP.

37. (#50 to 53 Answers) Calvin Cycle
Carbon Fixation (light independent reaction/Dark Reactions—does not require light energy)
C3 plants (80% of plants on earth)
Occurs in the stroma
Uses ATP and NADPH from light reaction as energy
Uses CO2
To produce glucose: it takes 6 turns and uses 18 ATP and 12 NADPH.

38. Chloroplast STROMA– where Calvin Cycle occurs Outer Membrane Thylakoid
Granum
Inner Membrane

39. Calvin Cycle (C3 fixation)
6CO2
6C-C-C-C-C-C
6C-C-C
6C-C-C-C-C
12PGA
RuBP
12G3P
(unstable)
6NADPH
6ATP
C-C-C-C-C-C
Glucose
(6C)
(36C)
(30C) C3
glucose

40. Calvin Cycle
Remember: C3 = Calvin Cycle C3
Glucose

41. Why do some plants close their stoma during the day?
Question:
Why do some plants close their stoma during the day?

42. Some plants close their stoma in the hottest part of the day to conserve water

43. Some Plants Hot, dry environments 5% of plants (cactus and ice plants)
Stoma (#54) closed during day
Stoma open during the night
Light reaction - occurs during the day
Calvin Cycle - occurs when CO2 is present