Photosynthesis Review

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

Photosynthesis

3. Using chemical formulas, write the balanced equation for photosynthesis.

4. Now write out the equation using words.

Carbon dioxide + water yields sugar + oxygen

6CO2 + 6H2O C6H12O6 + 6O2Sunlight

Photosynthesis

5. What organelle in plants is involved in photosynthesis?

The chloroplast

6. What gives it the green color?

The pigment chlorophyll

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.

Photosynthesis

8. Identify the chloroplasts in this micrograph of elodea cells.

Chloroplasts

Elodea plant Elodea plant cells

Photosynthesis

Identify the following structures of the chloroplast.

9

Photosynthesis

Identify the following structures of the chloroplast.Outer

membrane

Photosynthesis

Identify the following structures of the chloroplast.

10

Photosynthesis

Identify the following structures of the chloroplast.Inner

membrane

Photosynthesis

Identify the following structures of the chloroplast.

11

Photosynthesis

Identify the following structures of the chloroplast.

Inner membrane space

Photosynthesis

Identify the following structures of the chloroplast.

12

Photosynthesis

Identify the following structures of the chloroplast.Stroma

Photosynthesis

Identify the following structures of the chloroplast.

13

Photosynthesis

Identify the following structures of the chloroplast.

Thylakoids

Photosynthesis

Identify the following structures of the chloroplast.14

Photosynthesis

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

Photosynthesis

Identify the following structures of the chloroplast.

15

Photosynthesis

Identify the following structures of the chloroplast.

GranumA stack of thylakoids

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).

Photosynthesis

18. Where in the chloroplast do the light-dependent reactions occur?

The light-dependent reactions occur in the thylakoids

Photosynthesis

19. Where in the chloroplast do the light- independent reactions occur?

The light-independent reactions occur in the stroma.

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.

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.

PhotosynthesisThe 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.

Chloroplast22

24

23 2625

27

Photosynthesis

ChloroplastLight energy

23

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.

24

2625

27

Photosynthesis

ChloroplastLight energy

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.

24

2625

27

H2OWater

Photosynthesis

ChloroplastLight energy

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.

2625

27

H2O

O2

Water

Oxygen

Photosynthesis

ChloroplastLight energy

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.

26ATP

27

H2O

O2

Water

Oxygen

Photosynthesis

ChloroplastLight energy

H2O

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.

O2

CO2ATP

27

Water

Oxygen

Carbon dioxide

Photosynthesis

ChloroplastLight energy

H2O

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.

O2

CO2ATP

C6H12O6

Water

Oxygen

Carbon dioxide

Sugar (glucose)

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.

28. What do plants do with the sugars they make from photosynthesis?

Everything above can be made from sugars

Photosynthesis

The excess sugars are stored as starch.

29. What do plants do with the excess sugars they make during photosynthesis?

Starch grains (stained purple)

in plant cells.

Photosynthesis

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.

30. What will happen if a plant is placed in the dark for 48 hours?

Photosynthesis

a. Destarch a plant by leaving it in the dark for 48 hrs.b. Next, cover a section of one leaf with cardboard.

An Experiment in photosynthesis

c. Finally, expose the leaf to light for 24 hours

Photosynthesis

d. Remove cardboard and pick off the leaf.e. Put the leaf in hot water for a few minutes.

An Experiment in photosynthesis (continued)

PhotosynthesisAn Experiment in photosynthesis (continued)f. Remove the leaf.g. Test for starch using iodine solution.

Iodine Solution

PhotosynthesisAn Experiment in photosynthesis (continued)31. What do you think will happen?

Iodine Solution

PhotosynthesisAn 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.

The areas exposed to light would store starch and test positive with iodine, turning a black color.

No light, no starch

Exposure to light Positive for starch

Photosynthesis32. 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.

Photosynthesis33. Study the chart below. What color(s) of light does chlorophyll absorb best?

Chlorophyll absorbs red and blue light energies the best.

Photosynthesis34. 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.