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Information about exam 3 in the bio 311c course during spring 2009, focusing on photosynthesis and carbon fixation in plants. The lecture covers the differences between c3 and c4 photosynthesis, as well as the process of cam photosynthesis. Students are advised to bring a pencil for the exam and not to use calculators.
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Exam 3 on Friday will consist of 37 multiple choice questions and 4 additionalquestions that require you to write an directly answer on the exam.You will need to bring a pencil (and perhaps a back-up pencil) to the exam onFriday. Nothing else will be required. You will not need, and should not use, acalculator during the exam.
Mesophyll cell
Stomata
CO
2
O Vein^2
From textbook Figure10.3, p. 187
Cross-section of a Leaf of a Typical C
3
Plant Epidermis: prevents gasesfrom entering and leaving thechlolroplasts except throughstomata.
All photosynthetic cellsare directly exposed toCO
2
from the atmosphere.
C
4
Photosynthesis
2
2
2
Active transport Active transport
high CO
2
concentration
low CO
2
concentration
The first product of carbon dioxide fixation is a C
4
compound.
2
is pumped in this direction
ATP required
typical C
3
photosynthesis
2
from the atmosphere is covalently bound to
a C
3
organic molecule to produce a C
4
organic
molecule in a plant cell that is accessible to theatmosphere.
4
organic molecule is transported by active
transport to an adjacent cell that is not accessibleto the atmosphere.
2
is released from the C
4
molecule. The
regenerated C
3
molecule is then transported back
to the original cell, and the released CO
2
starts to
accumulate at high concentration.
2
into organic molecules because rubisco
functions efficiently at high CO
2
concentration.
C
4
Photosynthesis;
Occurs in some unusually fast-growing plants
From textbook Fig. 10.20, p. 202
4
mesophyllcell 3 bundlesheathcell
2
from the atmosphere is covalently bound to
a C
3
organic molecule to produce a C
4
organic
molecule in darkness while the leaf pores areopen so photosynthetic cells are exposed to theatmosphere.
4
organic molecule is transported by active
transport from the chloroplast to the centralvacuole by active transport.
atmosphere. CO
2
is then released from the C
4
molecule. The regenerated C
3
molecule is then
transported back to the chloroplast and thereleased CO
2
diffuses to the chloroplast, where it
starts to accumulate at high concentration.
2
during
daylight even though the leaf is sealed from theatmosphere.
CAM Photosynthesis;
Occurs in many desert plants
From textbook Fig. 10.20, p. 202
4
3
Food Assimilation and Energy Utilization
in a Photoautotrophic Organism (e.g. a plant)
A photoautotrophic organism obtains its source of energy fromlight. Plants are photoautotrophic organisms.
Operation of the Food Chain (Metabolic Perspective)
