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. 6CO2 + 6H2O C6H12O6 + 6O2 Sunlight 4. Now write out the equation using words. Carbon dioxide + water yields sugar + oxygen

Photosynthesis 5. What organelle in plants is involved in 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

Thylakoid space (lumen) 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. Granum A 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.

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

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

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

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

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

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

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)

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

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.

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.

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

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.

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

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

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

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.

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

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.