BIOEXCEL 190 - Photosynthesis


____.) Draw an arrow on the following figure to indicate the direction in which ernergy increases along the electromagnetic spectrum.

a. Describe the relationship between the wavelength and the energy of light.
b. Describe the relationship between the frequency and the energy of light.
c. Describe the relationship between the frequency, wavelength, and energy of light.

____.) What range of wavelengths comprises the visible spectrum?

____.) If an object appears blue, what color(s) does it absorb? What color(s) does it reflect?

____.) Why does the exterior of a black car in the summer sun get much hotter than the exterior of a white car?

____.) On the axes below, sketch the absorption spectrum for a pigment that appears reddish-orange.

____.) In 1883, Thomas Engelmann shone white light passed through a prism onto a test tube of filamentous greeen algae and aerobic bacteria. The figure below illustrates a) the absorption spectra for pigments extracted from chloroplasts; b) the action spectrum for photosynthesis across a range of wavelengths; and c) the results of Engelmann’s experiment.

a. Chloroplasts contain a variety of pigments, each of which absorbs specific wavelengths of light. Only chlorophyll a can participate directly in photosynthesis. What wavelength(s) and color(s) does it absorb?
b. Which wavelength(s) and color(s) are absorbed by chlorophyll b?
c. Which wavelength(s) and color(s) are absorbed by carotenoids?
d. What color does each of the 3 pigments appear in plant tissues?
Chlorophyll a =
Chlorophyll b =
Carotenoids =
e. Although only chlorophyll a is directly involved in photosynthesis, accessory pigments (such as chlorophyll b and carotenoids) can transfer the energy they absorb to the chlorophyll a molecules. What is the advantage of having these accessory pigment molecules, which make up an antenna?
f. How can you tell which wavelengths of light are photosynthetically active?
g. What color of light does not promote photosynthesis? Why not?
h. What environmental stimulus would attract aerobic bacteria?
i. Which regions of the electromagnetic spectrum attracted the bacteria? Why?

____.) Plants are photoautotrophs. What is their energy source? What is their carbon source?

____.) Do plants cells need to respire? Why or why not?

____.) The following statements seem to be contradictory, but they are both true. Explain.
“All life on Earth depends on energy from the sun.”
“Humans are chemoheterotrophs.”

____.) Fill in the blanks on the following figure:

____.) In what part of the chloroplast is water split?

____.) In what part of the chloroplast is the electron transport chain?

____.) What is the reducing agent for the ETC? What is the oxidizing agent for the ETC?

____.) Define photophosphorylation. How is it similar to substrate-level and oxidative reduction? What makes it unique?

____.) What molecule serves as the ultimate electron acceptor in noncyclic flow?

____.) In what part of the chloroplast is NADP+ reduced?

____.) The light reactions consist of both cyclic and noncyclic electron flow. Be sure that you can trace the paths of both routes of electron flow on the following figure:

a. What are the photosystems involved in noncyclic electron flow? What are the products formed?
b. What are the photosystems involved in cyclic electron flow? What are the products formed?
c. At any single photosystem complex, only cyclic or noncyclic flow can occur at one time. Why can’t the two electron pathways occur simultaneously?
d. Why is no oxygen generated by cyclic electron flow?
e. Why is it important to have both types of electron flow? (Hint: think about the input demands of the Calvin cycle.)
f. What conditions (for instance, concentration of a certain molecule…hint…hint!) regulate whether the flow of electrons will be cyclic or noncyclic?
g. How would the rate of sugar synthesis be affected if cyclic electron flow was disabled? Why? What would happen to the concentration of NADPH in the stroma?

____.) Chloroplasts can make carbohydrate in the dark if provided with:
a. photons and carbon dioxide
b. a source of hydrogen
c. organic acids or 4-carbon compounds
d. an artificially induced proton gradient
e. ATP and NADPH and carbon dioxide

____.) Which of the following is mismatched with its location?
a. light reactions - grana
b. electron transport chain – thylakoid membrane
c. Calvin cycle - stroma
d. ATP synthase – double membrane surrounding chloroplast
e. splitting of water – thylakoid compartment

____.) Determine the photosynthetic inputs and outputs required to synthesize 5 glucose molecules.
a. Inputs:
energy (type) =
water =
carbon dioxide =

b. Outputs:
energy (type) =
oxygen =
G3P =

____.) What is the evolutionary significance of photosynthesis? (Hint: think about Earth’s early atmosphere in comparison to today’s atmosphere.)

____.) Suppose you were able to measure the pH of both the thylakoid compartment and the stroma in a photosynthetically active plant cell.
a. What would you expect to find in terms of the relative (not absolute) pH of these two solutions? Why?
b. What would you expect the rate of sugar anabolism to be if the pH of the two solutions were equal? Why? Which photosynthetic outputs would not be affected in this situation?

____.) In order to reduce photorespiration, some plants have developed alternatives to the typical (C3) photosynthetic pathway (the one you have been studying). Refer to the following figure and match the following statements with one of the 2 diagrams, both of them, or neither of them.

a. C4 metabolism =
b. CAM metabolism =
c. The light reactions are temporally separated from the Calvin cycle =
d. The light reactions are spatially separated from the Calvin cycle =
e. Incorporates carbon dioxide into organic acids before it enters the Calvin cycle =
f. Completes the light reaction =
g. Common in sugarcane, corn, and grasses =
h. Common in pineapples, cacti, and other succulents =
i. The Calvin cycle takes place in bundle sheath cells =
j. Evolutionary adaptation to maintaining photosynthesis with stomata partially or completely closed on hot dry days
k. avoids photorespiration by fixing carbon dioxide into organic acids during the night

____.) Summarize C4 metabolism.

____.) Summarize CAM metabolism.

____.) Indicate if the following events occur during:
A. respiration
B. photosynthesis
C. both respiration and photosynthesis
D. neither respiration nor photosynthesis

Chemiosmotic synthesis of ATP =
Reduction of oxygen =
Reduction of carbon dioxide =
Reduction of NAD+ =
Oxidation of water =
Oxidation of NADP+ =
Oxidation of glucose =
Oxidative phosphorylation =
Electron flow along an electron transport chain =
An exothermic redox reaction =
An endothermic redox reaction =
Conversion of light energy into chemical energy =

© 2002-2003 Kevin Hong