Group : Gerber, Kyle, Luis,
Nathan, Robbie, Chris, Nathan,
Jake
PHOTORESPIRATION
What is photorespiration?
Photorespiration occurs when carbon
dioxide levels inside the leaf becomes low
and begins the process in which plants
inhibit the Calvin cycle by using oxygen,
which prevents the carbon fixation portion
of photosynthesis. This is due to the reason
that the CO2 fixing enzyme RUBP
carboxylase not only accepts CO2 but can
also combine with O2. Since the reaction is
an oxygenation reaction, the same enzyme
is called RUBP oxygenase.
Facts about photorespiration
Photorespiration occurs when the
stomata on a leaf/plant are forced to
close in dry conditions to prevent
excess water loss. This prevents the
plant from respirating regularly,
(bringing in CO2 and releasing
Oxygen). Since CO2 is one of the
main reactants in the creation of
glucose, doing without it can restrict
the plants ability to make energy. So
doing this process for too long can
hurt the plant.
How Photorespiration Works (The Process)
Photorespiration is a process in plant metabolism in
which the plant attempts to reduce the consequences of
wasteful oxygenation by restricting the enzyme Rubisco.
When the CO2 levels inside the leaf drop to about 50
ppm (parts per million), Rubisco starts to combine O2
with RuBP instead of CO2. The net result of this is one
molecule of PGA and a toxin called phosphoglycolate.
The plant needs to get rid of the phosphoglycolate, so it
gets rid of the phosphate group, converting it to glycolic
acid. The acid is then transported to the peroxisome
where it turns to glycine. Afterwards it is sent to the
mitochondria to be converted into serine. This serine
produced is very useful as it is used to make other
organic molecules. However, all of these conversions
cost energy and result in a loss of CO2.
Questions
What does photorespiration inhibit?
What enzyme is restricted during photorespiration?
When does photorespiration occur?
Where does photorespiration occur?
Works Cited
http://www2.mcdaniel.edu/Biology/botf99/photodark/photorespiration.htm
http://www.tutorvista.com/content/biology/biologyiv/photosynthesis/photorespiration.php :)