Exam 3 Homework Essay

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Chapter 8 – Homework
1. How are photosynthesis and respiration linked?
a. They are opposites of each other.
2. List the three stages of photosynthesis and indicate the light dependent reactions and the light independent reactions.
Capturing energy from sunlight (dependent)
Using energy to make ATP and NADPH (dependent)
Using ATP and NADPH to power the synthesis of carbohydrates from CO2
2. Which has more energy shorter wavelengths or longer wavelengths? short 3. What are pigments? List the pigments found in plants and indicate the pigment most important for photosynthesis.
Carotenoids– Assist chlorophyll by capturing energy in a wavelength not efficiently absorbed by chlorophylls
Chlorophylls (most important)
Chlorophyll a
Main photosynthetic pigment; only one that can directly convert light energy to chemical energy
Chlorophyll b
Accessory pigment; compliments and adds to absorption of chlorophyll a
4. What are the four stages of the light dependent reactions?
Primary Photo Event– Photon captured by pigment – results in excitation of electron in pigment
Charge separation
Excitation energy transferred specialized chlorophyll pigment called reaction center = reacts by transferring electron to acceptor molecule initiating electron transport
Electron transport
Excited electron shuttled along series of electron carrier molecules embedded in photosynthetic membrane – transport protons across membrane generating a proton gradient –electron then passed to final acceptor
Protons accumulate then flow back across membrane through specific protein complexes chemiosmotic synthesis ATP takes place
5. What is the function of the photosystem (include antenna complex and reaction center in your explanation)?
Photosystems = clusters of chlorophylls and accessory pigments
Captures light energy
Composed 2 components
Antenna complex – hundreds of pigment molecules
Captures photons form sunlight
Funnels energy from many electrons to reaction center
Reaction center – one or more chlorophyll molecules
Passes energy out of photosystem to an electron acceptor that is part of the electron transport chain

6. Describe cyclic electron flow or cyclic photophosphorylation? What product is generated?
7. Describe noncyclic electron flow or noncyclic photophosphorylation? Include the correct order of proteins the electron is transported to during the pathway from photosystem II to photosysytem I? And from photosystem I to NADPH? What product is generated?
a. Photons of light excited electrons in the antenna complex of photosystem
b. Antenna complex funnels energy to reaction center
c. Reaction center passes electron to a acceptor molecule that shuttles electron along the electron transport chain
d. Energy being release as electron travels down electron transport chain is used generate a proton gradient
e. Proton gradient is used to generate ATP by chemiosmosis
f. Once all the energy has be extracted from the excited electron, the electron returns to the photosystem to be excited again by another photon of light
g. Cycle because the electron starts at the photosystem and then returns to the photosystem
h. Net yield is only ATP
8. Explain the chemiosmotic model of ATP formation? Where is the hydrogen ion concentration gradient high?
a. The pumping of protons into the thylakiod compartment as well as the splitting of water which releases protons in the thylakoid compartment, generates a concentration gradient
b. Thylakiod compartment = high proton concentration
c. Stroma = low proton concentration
d. Protons diffuse into stroma through specific channels that synthesize ATP
e. ATP synthase
f. ATP is therefore made in the stroma
9. Explain the Calvin-Benson Cycle? What are the reactants and products? Where does the Calvin-Benson Cycle take place? What molecule is regenerated?
10. Write the equation for photosynthesis.
a. 6CO2 + 12H2O sunlight/chlorophyll→ C6H12O6 + 6H2O + 6O2

Chapter 10 & 11- homework
1. Explain cell division in prokaryotes.