1. Photosynthesis Review

2. Photosynthesis 1. Define photosynthesis.
Photosynthesis is the process by which photosynthetic organisms convert solar energy into chemical energy stored in sugars.
2. Name several photosynthetic organisms.
Trees
Algae
Cyanobacteria

3. Photosynthesis 3. Using chemical formulas, write the balanced
equation for photosynthesis.
6CO H2O C6H12O O2
Sunlight
4. Now write out the equation using words.
Carbon dioxide + water yields sugar + oxygen

4. Photosynthesis 5. What organelle in plants is involved in
The chloroplast
6. What gives it the green color?
The pigment chlorophyll

5. Photosynthesis 7. Where in plants are chloroplasts found?
In the cells of soft plant tissue, like the green stems and leaves of celery .
Note: Chloroplasts are also found in other colors of soft plant tissue, like the red leaves of a burning bush for example. They use secondary pigments, like carotenoids (orange color) and xanthophylls (yellow color) that are more predominant than green chlorophyll.

6. Photosynthesis 8. Identify the chloroplasts in this micrograph of
elodea cells.
Chloroplasts
Elodea plant
Elodea plant cells

7. Photosynthesis
Identify the following structures of the chloroplast. 9

8. Photosynthesis Identify the following structures of the chloroplast.
Outer membrane

9. Photosynthesis Identify the following structures of the chloroplast.10

10. Photosynthesis Identify the following structures of the chloroplast.
Inner membrane

11. Photosynthesis Identify the following structures of the chloroplast.11

12. Photosynthesis Identify the following structures of the chloroplast.
Inner membrane space

13. Photosynthesis Identify the following structures of the chloroplast.12

14. Photosynthesis Identify the following structures of the chloroplast.
Stroma

15. Photosynthesis Identify the following structures of the chloroplast.13

16. Photosynthesis Identify the following structures of the chloroplast.
Thylakoids

17. Photosynthesis Identify the following structures of the chloroplast.14

18. Thylakoid space (lumen)
Photosynthesis
Identify the following structures of the chloroplast.
Thylakoid space (lumen)

19. Photosynthesis Identify the following structures of the chloroplast.15

20. Photosynthesis Identify the following structures of the chloroplast.
Granum
A stack of thylakoids

21. Photosynthesis 16. Photosynthesis occurs in two parts. One is
the light-dependent reaction. What is the
other part called?
The other is the light-independent reaction.
17. Which of these two reactions can occur during
both the daytime and nighttime?
The light-independent reaction
(it doesn’t require light).

22. Photosynthesis 18. Where in the chloroplast do the light-dependent
reactions occur?
The light-dependent reactions occur in the thylakoids

23. Photosynthesis 19. Where in the chloroplast do the light-
independent reactions occur?
The light-independent reactions occur in the stroma.

24. Photosynthesis 20. Sometimes the light-independent reaction is
called the “dark” reaction. Why is dark reaction
not an appropriate term to use?
The use of the word dark makes one think that the reaction only occurs in the dark. This is not true since the reactions can take place in the light too—it is just light is not required for the reaction to occur.

25. Photosynthesis 21. What is another name for the light-independent
reactions that occur in the stroma?
The light-independent reaction is also called the Calvin Cycle, in honor of Melvin Calvin, who worked out the metabolic pathway of photosynthesis.
Chloroplast
Also known as the light-independent reaction.

26. Photosynthesis
The bean-shaped object below represents a chloroplast. The green disks are thylakoids and the tan area is the stroma. Identify the outputs and inputs of the light-dependent and light-independent (Calvin cycle) reactions. 23 25 26
Chloroplast 22 24 27

27. Photosynthesis 23 25 26 Light energy 24 27
The bean-shaped object below represents a chloroplast. The green disks are thylakoids and the tan area is the stroma. Identify the outputs and inputs of the light-dependent and light-independent (Calvin cycle) reactions. 23 25 26
Light energy
Chloroplast 24 27

28. Photosynthesis H2O 25 26 Light energy 24 27
The bean-shaped object below represents a chloroplast. The green disks are thylakoids and the tan area is the stroma. Identify the outputs and inputs of the light-dependent and light-independent (Calvin cycle) reactions.
Water
H2O 25 26
Light energy
Chloroplast 24 27

29. Photosynthesis H2O 25 26 Light energy O2 27
The bean-shaped object below represents a chloroplast. The green disks are thylakoids and the tan area is the stroma. Identify the outputs and inputs of the light-dependent and light-independent (Calvin cycle) reactions.
Water
H2O 25 26
Light energy
Chloroplast O2 27
Oxygen

30. Photosynthesis H2O ATP 26 Light energy O2 27
The bean-shaped object below represents a chloroplast. The green disks are thylakoids and the tan area is the stroma. Identify the outputs and inputs of the light-dependent and light-independent (Calvin cycle) reactions.
H2O
ATP
Water 26
Light energy
Chloroplast O2 27
Oxygen

31. Photosynthesis H2O ATP CO2 Light energy O2 27
The bean-shaped object below represents a chloroplast. The green disks are thylakoids and the tan area is the stroma. Identify the outputs and inputs of the light-dependent and light-independent (Calvin cycle) reactions.
ATP
Water
H2O
CO2
Carbon dioxide
Light energy
Chloroplast O2 27
Oxygen

32. Photosynthesis H2O ATP CO2 Light energy O2 C6H12O6
The bean-shaped object below represents a chloroplast. The green disks are thylakoids and the tan area is the stroma. Identify the outputs and inputs of the light-dependent and light-independent (Calvin cycle) reactions.
H2O
ATP
Water
CO2
Carbon dioxide
Light energy
Chloroplast O2
Oxygen
C6H12O6
Sugar (glucose)

33. Everything above can be made from sugars
Photosynthesis
28. What do plants do with the sugars they make
from photosynthesis?
The sugars are used to help the plant live, grow, and reproduce. Some sugars are used to make other compounds, and some end up at the mitochondria to be converted into ATP, which is then used to drive cellular reactions.
Everything above can be made from sugars

34. Starch grains (stained purple) in plant cells.
Photosynthesis
29. What do plants do with the excess sugars they
make during photosynthesis?
The excess sugars are stored as starch.
Starch grains (stained purple) in plant cells.

35. Photosynthesis 30. What will happen if a plant is placed in the dark
for 48 hours?
Since it will not be able to make glucose through photosynthesis, the plant must access glucose from starch reserves. The plant will most likely deplete its starch supply in that time. Thus the plant will be destarched.

36. Photosynthesis An Experiment in photosynthesis
a. Destarch a plant by leaving it in the dark for 48 hrs.
b. Next, cover a section of one leaf with cardboard.
c. Finally, expose the leaf to light for 24 hours

37. Photosynthesis An Experiment in photosynthesis (continued)
d. Remove cardboard and pick off the leaf.
e. Put the leaf in hot water for a few minutes.

38. Photosynthesis An Experiment in photosynthesis (continued)
f. Remove the leaf.
g. Test for starch using iodine solution.
Iodine Solution

39. Photosynthesis An Experiment in photosynthesis (continued)
31. What do you think will happen?
Iodine Solution

40. Exposure to light Positive for starch
Photosynthesis
An Experiment in photosynthesis (continued)
31. What do you think will happen?
The leaf cells under the cardboard would not receive any light and thus would not make sugars or store any starch.
No light, no starch
The areas exposed to light would store starch and test positive with iodine, turning a black color.
Exposure to light Positive for starch

41. Photosynthesis 32. As previously mentioned, chlorophyll is green. Why
is chlorophyll green and not some other color?
White light is made up of many colors. Chlorophyll absorbs all of these colors except green, which is reflected back into our eyes.

42. Photosynthesis 33. Study the chart below. What color(s) of light does
chlorophyll absorb best?
Chlorophyll absorbs red and blue light energies the best.

43. Photosynthesis 34. What would happen to the health of a plant that
was grown under red and blue filters?
The plant will do poorly since the red and blue light energies chlorophyll absorbs best are being reflected away by the filters.