BY 123 SI Session #6 Answer Key
Chapter 10: Photosynthesis
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#1) What is the chemical formula for photosynthesis? What is oxidized? Reduced? What is the
oxidizing agent? Reducing agent?
ENERGY + 6CO2(reduced) + 6 H2O(oxidixed)  C6H12O6(oxidizing agent) + 6 O2(reducing
agent)
#2) Order the steps of the Light Reactions:
__5___ photoexcited electrons pass from the primary electron acceptor of PS II to PS I.
_8____ NADP+ reductase catalyzes the transfer of electrons from PS I to NADP+. 2 electrons
Reduce NADP+ to NADPH.
__1___ A photon of light strikes a pigment molecule in PS II, energy is relayed to other pigment
molecules until it reaches P680 pair of chlorophyll molecules.
__4___ The fall of electrons from PS II to PS I produces energy for ATP synthesis. Electrons
pass through the cytochrome complex and H+ are pumped into the thylakoid lumen establishing a
proton gradient.
__2___ excited electrons are transferred from P680 to the primary electron acceptor.
__6___ light harvesting complex pigments transfer light energy to PS I, which excites an
electron of P700. The photoexcited electron is then transferred to PS I’s primary electron
acceptor.
__3___ A water molecule is split into two H+ ions and an oxygen atom. The electrons are
supplied to P680, replacing one that has been sent to the primary electron acceptor of PS II.
__7___ photoexcited electrons are passed down a second electron transport chain.
#3) Order the steps of the Calvin Cycle:
__3___ Each three carbon sugar receives a second phosphate group from the hydrolysis of ATP.
_1____ Each CO2 molecule is incorporated into the Calvin Cycle by attachment to a 5 Carbon
sugar named RuBP (rubilose biphosphate). Rubisco is the enzyme that catalyzes this step.
__4___ NADPH reduces the three carbon sugar with two phosphate groups, and G3P is
produced.
__6___ 5 G3P molecules are rearranged into 3 molecules of RuBP with the help of ATP.
__2___ A short lived 6 Carbon intermediate with two phosphates is split into a three Carbon
sugar with one phosphate.
__5___ One molecule of G3P exits the cycle and 5 molecules of G3P continue in the cycle.
#4)How many turns of the Calvin Cycle does it take to produce one molecule of glucose?
a.
b.
c.
d.
e.
1
2
3
6
12
#5) Which of the following sequences correctly represents the flow of electrons during
photosynthesis?
a.
b.
c.
d.
e.
H2O  NADPH  Calvin Cycle
NADPH  electron transport chain  CO2
H2O  photosystem I  photosystem II
NADPH  O2  CO2
NADPH  chlorophyll  Calvin Cycle
#6) How is photosynthesis similar in both C4 plants and CAM plants?
a.
b.
c.
d.
e.
In both cases, Rubisco is not used to fix carbon initially
In both cases thylakoids are not involved in photosynthesis
Both make sugar without the Calvin Cycle
In both cases, only photosystem I is used
They both make most of their sugar in the dark
#7) Which is the C4 plant and which is the CAM plant?
a. Carbon fixation and the Calvin Cycle occur in the same cells at different times. CAM
b. Carbon fixation and the Calvin Cycle occur in different types of cells.C4