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35 Cards in this Set

  • Front
  • Back
What are the products of teh oxygenation of ribulose-1,5-bisphosphate by rubisco and what is the oxygenation referred to as?
3-phosphoglycerate and 2-phosphoglycolate
What evidence is there that photorespiration is not an adaptation to elevating oxygen concentration in our atmosphere?
because photorespiration is used in high and low concentrations of atmospheric CO2
What three organelles are involved in photorespiration and the eventual production of 3-phosphoglycerate from the 2-phosphoglycolate?
Chloroplast, Peroxisome, Mitochondrion
What three factors determine the balance between photorespiration and carbon fixation and the Calvin Benson Cycle?
Kinetic properties of rubisco, temperature, and the environment
What benefit might there be for photorespiration?
it makes nitrates more available to plants
What two approaches are genetic engineers taking to engineer crops that have reduced photorespiratory taxes and which of these have been successful?
Successful mutations that knock out photorespiration
When did the pronounced reduction in CO2 and increase in oxygen occur and what are the consequences of that for plants?
350 million years ago, adaptations that promoted photorespiration like C4 and CAM
What are two mechanisms for concentrating CO2 at the rubisco active site?
C4 and CAM
How did Kortschack and Karpilov discover C4 photosynthesis?
Added CO2 to sugarcane corn --->70-80% of label was found in C4 acids, (Malate and Aspartate)
What enzyme catalyzes the primary carboxylation step in C4 plants and where does this step occur?
PEPCase= periphery of leaf cells (external region)
Which has more chloroplasts, mesophyll or bundle sheath cells?
bundle sheath cells (Internal ring)
Why do C4 plants do better in hot dry climates?
because they don't need to keep their stomata open
When did C4 and CAM photosynthesis evolve?
in the last 35 million years
When do CAM plants take in CO2 and do CAM plants have the same anatomical separation of carbon fixation and reduction that C4 plants do?
CAM plants take in CO2 at night and stores it in the vacuole
What enzyme is used to fix CO2 at night in CAM plants and where is the four carbon acid stored?
Cytosolic Pepcase ----> acid vacuole
Describe typical anatomical features of CAM plants.
succulents
Why might aquatic plants use the CAM photosynthetic pathway?
?
In what cell compartments are starch and sucrose made, respectively?
starch is made in the chloroplasts durring the day.
Sucrose is made in the cytosol
When is chloroplast starch degraded into sucrose?
at night
How many factors can limit photosynthesis at one time?
one
What three major metabolic properties have been identified as being important for optimal photosynthetic performance?
-Rubisco Activity
-Regeneration of rubulose bisphosphate (RuBP)
-Metabolism of the triose phosphate
What was Farquar and Sharky's new perspective on how we should think about controls on the overall rate of photosynthesis?
in terms of economics
What equation gives the energy of a photon, define each term.
E=hc/λ
What is photosynthetically active radiation or PAR?
Light of wavelengths between 400 to 700 nm range that corresponds to the wave band absorbed by photosynthetic pigments
How does irradiance vary with carrying angles of incidence on a leaf and how/where do you measure this angle?
?
How much PAR is there on a sunny day?
sunny day is 2,000 μmol, dense canopy is 10 μmol
Why is only about 5% of the incident radiation on earth used by photosynthesis?
1/2 the incident light is a wavelength too short or too long to be absorbed by the photosynthetic pigments.
How do epidermal cells maximize light capture?
The epidermis is typically transparent, and the epidermal cells are convex which helps focus light on the chloroplasts
Is it likely that desert plants would have convex epidermal cells and palisade parenchyma? Why?
No, because there is already too much light and it can be harmful to leaves
Sunflects can account for up to X amount of the total light energy available for photosynthesis in some habitat.
50%
What kind of light, and what types of cells, control the solar tracking of leaves?
Blue light, the palvinus is a specialized organ which contains motor cells that change their osmotic potential and generate mechanical forces that determine laminar orientation.
What is the difference between acclimation and adaptation?
acclimated plants can go from inside to outside and change to fit the environment. Adapted plants would probably die if they went from inside to outside because they don't change to fit the environment
Do shade leaves typically have more or less chlorophyll per reaction center?
more
Do shade leaves have more or less xanthophyll pigments and rubisco?
less
What type of light is proportionally more abundant in shade environments?
Far-red which is absorbed primarily by PSI