5.2.3 Photosynthetic Pigments Flashcards
1
Q
pigments
A
- Substances that are able to absorb light
2
Q
photosynthetic pigments
A
- such as chlorophyll are able to absorb light so that its energy may be used to build carbohydrates during photosynthesis.
3
Q
chlorophyll
A
- chlorophyll is a green pigment found embedded in the thylakoid membrane of chloroplasts. Chlorophyll a is the pigment involved directly in the light reactions of photosynthesis. Other pigments in plant cells include chlorophyll b and carotenoids
4
Q
Engelmann
A
- In 1883 Thomas Engelmann showed that algae were able to use blue and red wavelengths of light more effectively than green wavelengths of light to perform photosynthesis
- Engelmann showed how different wavelengths of light
affected the rate of photosynthesis in filamentous algae. The algae were photosynthetic and had a long spiral chloroplast within them. As shown in the illustration, Engelmann used a prism to split white light into its component colors and shined the light along the length of the alga. - He then used aerobic bacteria that clustered around oxygen sources to determine which part of the alga was releasing oxygen.
- The bacteria clustered around areas that were exposed to blue and red light, and did not cluster around areas exposed to green light, demonstrating the action spectrum for photosynthesis.
5
Q
action spectrum
A
- shows the effectiveness of different wavelengths of light on photosynthesis. There is some photosynthetic activity in the green range (500 - 600 nm) because of the presence of accessory pigments such as carotenoids.
- The absorption spectrum of chlorophyll b peaks at the
wavelengths where the absorption of chlorophyll a begins to dip. Also note that carotenoids absorb wavelengths of light that chlorophylls a and b do not.
6
Q
Which statement is not true?
A
- Chlorophyll a is green because it absorbs green wavelengths
7
Q
True or false?
Leaves appear green to us because green light is mostly absorbed by chlorophyll a.
A
- false
8
Q
True or false?
Chlorophyll b and carotenoids are pigments used by plants to increase the wavelengths of light that can be used for photosynthesis.
A
- true
9
Q
Chlorophyll’s absorption spectrum
A
- explains why chlorophyll is green
10
Q
The relative effectiveness of different wavelengths of light on the rate of photosynthesis is shown by
A
- an action spectrum
11
Q
An action spectrum for a plant has less extreme peaks and valleys than an absorption spectrum for chlorophyll a of the same plant because
A
- an action spectrum reflects the presence of other pigments in the plant
