# Mastering Biology Homework: Photosynthesis

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Which of these equations best summarizes photosynthesis?
- 6 CO2 + 6 O2 → C6H12O6 + 6 H2O
- C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
- 6 CO2 + 6 H2O → C6H12O6 + 6 O2
- C6H12O6 + 6 O2 → 6 CO2 + 12 H2O
- H2O → 2 H+ + 1/2 O2 + 2e-
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Terms in this set (35)
a. sunlight
b. photosynthesis
c. chloroplasts
d. sugar
e. chlorophyll
f. cellular respiration
g. mitochondria
h. carbon dioxide
(A mutually dependent relationship exists between chloroplasts and mitochondria in the plant cell. Photosynthesis, which occurs in chloroplasts, generates the sugars and oxygen gas that are used in mitochondria for cellular respiration. Cellular respiration generates carbon dioxide, which in turn is used as a carbon source for the synthesis of sugars during photosynthesis. Cellular respiration also generates ATP and water, which are used in various chemical reactions in the plant cell)
In Engelmann's experiment, he used aerotactic (oxygen-seeking) bacteria to determine which wavelengths of visible light were most effective in driving the reactions of photosynthesis in green algae. A diagram of his apparatus is shown below. Can you deduce the logical link between light of different wavelengths and the distribution of bacteria that Engelmann observed?

1. Sun emits photons at all wavelengths
....
7. Number of bacteria in different wavelength regions counted.
Engelmann counted the number of bacteria that were attracted to the algal filament associated with each color of light. As shown in the image below, most of the bacteria were attracted to the regions of the alga illuminated by red or violet-blue light. This distribution of bacteria shows that red and violet-blue wavelengths are most effective in driving photosynthesis. By measuring oxygen production with aerotactic bacteria, Engelmann described an action spectrum for photosynthesis. The action spectrum (indicated by the black line plot in the image above) shows the relative effectiveness of each color of light in driving photosynthesis.
What assumptions did Engelmann make in order to conclude that red and violet-blue light were more effective than green light in driving photosynthesis? Select the two that apply.
- Every photon absorbed by the alga was used to drive oxygen production by the alga
- The distribution of chloroplasts within each algal cell was approximately the same
- The number of bacteria clusters at each wavelength (color) was approximately proportional to the amount of oxygen being produced by that portion of alga
- The alga absorbed the same number of photons at each wavelength (color)
- The distribution of chloroplasts within each algal cell was approximately the same
- The number of bacteria clusters at each wavelength (color) was approximately proportional to the amount of oxygen being produced by that portion of alga
(Assumed:
1. The number of bacteria at any location on the slide was proportional to the amount of oxygen produced by the alga at that location
2. The distribution of chloroplasts among the cells in the algal filament was approximately equal
Not assumed:
1. The alga absorbed the same number of photons at each wavelength
2. All absorbed photons drive photosynthesis, and thus oxygen production, by the alga
Photosystem II (PS II) only:
- Oxidation of water
- Reduction of electron transport chain between the two photosystem
Photosystem I (PS I) only:
- Oxidation of electron transport chain between the two photosystems