PACKET #31 CHAPTER #10 Photorespiration. Introduction Plants that use the Calvin Cycle to fix...
-
Upload
elfrieda-phillips -
Category
Documents
-
view
215 -
download
0
Transcript of PACKET #31 CHAPTER #10 Photorespiration. Introduction Plants that use the Calvin Cycle to fix...
PACKET #31CHAPTER #10
Photorespiration
Introduction
Plants that use the Calvin Cycle to fix carbon, in the molecule sugar, are called C3 plants.
During photorespiration, C3 plants consume oxygen and generate CO2 but do not produce ATP Conserving water and preventing passage of CO2 into the
leafPhotorespiration is said to be an evolutionary
relic and lowers the efficiency of photosynthesis by removing carbon molecules from the Calvin Cycle. Photorespiration reduces the rate of photosynthesis.
Introduction II
Photorespiration reduces the rate of photosynthesis in plants in three ways Carbon dioxide is released Energy (ATP) is diverted from photosynthetic
reactions to photorespiratory reactions. Competition between oxygen and carbon dioxide
reduces the efficiency of the important photosynthetic enzyme ribulose-bisphosphate (RuBP) carboxylase.
Photorespiration in C3 Plants
On dry, hot days in the presence of light C3 plants close their stomata.
This causes the plant to use of oxygen, similar to aerobic cellular respiration, and produce CO2 and H2O.
C4 and CAM Plants
C4 & CAM Plants Introduction
C4 and CAM plants have devised mechanisms that prevent/reduce the impact of photorespiration.
C4 Plants
Photorespiration & C4 Plants
Photorespiration is negligible in C4 plants because the concentration of carbon dioxide is always high in the bundle sheath cells.
Photorespiration & C4 Plants II
In C4 plants, during hot dry periods, oxygen molecules in the chloroplast bind with Rubisco and prevent carbon fixation.
RuBP and oxygen combine, and the intermediates in the Calvin Cycle degrade to form CO2 and water.
Pathway in C4 Plants
C4 Plants
Developed a technique to reduce the occurrence of photorespiration
PEP carboxylase binds CO2 Even at low concentrations
CO2 is fixed into oxaloacetate
Oxaloacetate is converted to malate Malate moves into a bundle
sheath cell while CO2 is removed
CO2 enters the Calvin Cycle
CAM Plants
CAM Plants
CAM is an acronym for crassulacean acid metabolism.
Examples Succulent plants {family
Crassulaceae} Family Cactaceae Family Lilaceae Family Orchidaceae Many others in 25 families.
Plants exhibit a pathway similar to C4 plants and allow them to live in highly xeric conditions.
CAM Plants
PEP carboxylase fixes carbon at night in the mesophyll cells Stomata are open at
night Minimizes water loss
and allows the entry of CO2
Calvin Cycle occurs during the daytime
Homework Assignment
What are some of the similarities, and differences, between C4 and CAM plants?