7^th Grade Science Photosynthesis Name: _______________________

1. Photosynthesis means:

2. Photosynthesis takes place in:

a) Animals b) Plants c) Fungi d) None of these

3. Which molecule is first split in photosynthesis?

a) Sugar b) Carbon dioxide c) Water d) Oxygen

4. Which molecule is a by-product of photosynthesis and released into the air?

a) Hydrogen b) Carbon dioxide c) Water d) Oxygen

5. Green pigment responsible for capturing light for photosynthesis:

a) Chlorophyll b) Anthocyanins c) RUBISCO d) ATP

6. The typical plant is a : a) producer b) consumer

7. Chlorophyll is found in which cell organelle?

a) Nucleus b) Mitochondrion c) Chloroplast d) Golgi

8. What color of light can a green plant NOT utilize? ______________________

9. Molecules capturing extra light for the chlorophyll:

a) Chlorophyll b) Anthocyanins c) RUBISCO d) ATP

10. Enzyme that fixes carbon dioxide onto a sugar structure?

a) Chlorophyll b) Anthocyanins c) RUBISCO d) ATP

11. The chloroplast is most similar to what other cell organelle?

a) Vacuole b) Mitochondrion c) Cell Wall d) Golgi

12. First food molecule made by a green plant:

a) Sugar b) Carbon dioxide c) Water d) Oxygen

13. Pigment responsible for bright red leaves in autumn:

a) Chlorophyll b) Anthocyanins c) RUBISCO d) ATP

14. Wood is made of cellulose. Cellulose is made from:

a) Sugar b) ATP c) DNA d) Water

15. Coal comes from: a) Volcanoes b) Uneaten ancient plants

c) Dinosaur bones d) None of these

16. Describe the plants in your terrarium:
Chemistry of Autumn Leaf Color: How Fall Colors Work

The color of a leaf results from an interaction of different pigments produced by the plant. The main pigment classes responsible for leaf color are porphyrins, carotenoids, and flavonoids. The color that we perceive depends on the amount and types of the pigments that are present. Chemical interactions within the plant, particularly in response to acidity (pH) also affect the leaf color.

The primary porphyrin in leaves is a green pigment called chlorophyll. There are different chemical forms of chlorophyll (e.g., chlorophyll a and chlorophyll b), which are responsible for carbohydrate synthesis within a plant. Chlorophyll is produced in response to sunlight. As the seasons change and the amount of sunlight decreases, less chlorophyll is produced, and the leaves appear less green. Chlorophyll is broken down into simpler compounds at a constant rate, so green leaf color will gradually fade as chlorophyll production slows or stops.

Examples of carotenoids found in leaves include lycopene, which is red, and xanthophyll, which is yellow. Light is not needed in order for a plant to produce carotenoids, therefore these pigments are always present in a living plant. Also, carotenoids decompose very slowly as compared to chlorophyll.

Examples of flavonoids include flavone and flavol, which are yellow, and the anthocyanins, which may be red, blue, or purple, depending on pH. Anthocyanins, such as cyanidin, provide a natural sunscreen for plants. Because the molecular structure of an anthocyanin includes a sugar, production of this class of pigments is dependent on the availability of carbohydrates within a plant. Anthocyanin color changes with pH, so soil acidity affects leaf color. Anthocyanin production also requires light, so sunny days are needed for the brightest fall colors!

When leaves appear green, it is because they contain an abundance of chlorophyll. Chlorophyll masks other pigment colors. Anthocyanins, in turn, mask carotenoids. As summer turns to autumn, decreasing light levels cause chlorophyll production to slow. However, the decomposition rate of chlorophyll remains constant, so the green color will fade from the leaves. At the same time, anthocyanin production in leaves increases, in response to surging sugar concentrations. Leaves containing primarily anthocyanins will appear red. Leaves with good amounts of both anthocyanins and carotenoids will appear orange. Leaves with carotenoids but little or no anthocyanins will appear yellow. In the absence of these pigments, other plant chemicals also can affect leaf color. An example includes tannins, which are responsible for the brownish color of some oak leaves.

17. This article is about:

18. The strongest pigment that will mask all others is: _________________________

19. Can acidity change the color of anthocyanins? YES or NO

20. Do our leaves in Mississippi change this much? YES or NO

Why do you think this is so?