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UNK biol106- Light Independent Reactions of Photosynthesis
Terms in this set (30)
Purpose of light independent reactions?
Stroma of chloroplasts
Where do light independent reactions take place?
-calvin cycle also called C3 photosynthesis
Basic form of light independent reactions
Modified forms of light independent reactions
-most plants use this type
-common to temperate plants
-3-phosphoglycerate first product (3 carbon)
-included many grasses in arid climates
-first product is a 4 carbon oxaloacetate
-first discovered in sugarcane (tropical grass)
-common to cacti (very dry locations)
-take in CO2 at night using PEPCO which is stored as malate in the cell vacuole to use in the day because the plant can't afford to lose any water
-mose important enzyme on Earth
-used to get food
-starts off the C3 process
RUBP + CO2 with the help of rubisco gives 3 phosphoglycerate (x2)
What goes in and comes out of C3 photosynthesis?
-rubisco mistakes O2 for CO2 and starts photorespiration when the stomates are closed
-wastes resources and creates damaging peroxides
Problems that arise in C3 photosynthesis
Why doesn't C3 photosynthesis work for everything?
-RUBP + O2 with rubisco yields 3 phosphoglycerate + 2 phosphoglycollate
-the products are toxic
What is bad about photorespiration?
-produce free radicals
-will destroy/damage chloroplasts because they react with chloroplasts membranes and break them down
Function of peroxides in photorespiration
-increase in oxygen
-decrease in carbon dioxide
-high photosynthesis rate
Causes of photorespiration
How can photorespiration be avoided?
-spongy mesophyll: CO2 uptake from the air
-bundle sheath: carbohydrate synthesis
Cell types of C4 photosynthesis
-cope with photorespiration by separating CO2 uptake from air in one cell type and carbohydrate synthesis in another cell type
How does C4 photosynthesis cope with photorespiration?
Enzyme involved with C4 photosynthesis?
CO2 + phosphenolpyruvate (PEP) with help from PEPCO to yield oxaloacetate (4C)
What goes in and out of C4 photosynthesis?
-C4 photosynthesis has the enzyme flooded with CO2 to prevent the mistake of O2
-uses more energy but saves in the long run
-increases [CO2] in bundle sheath so that photorespiration can't occur easily
-no rubisco mistakes
How is C4 better than C3 photosynthesis?
-palisade and spongy mesophyll
-coming out of stomates: oxygen and water
-going in stomates: CO2
-net result: increase oxygen and decrease CO2
-spongy mesophyll- CO2 uptake
-bundle sheath- carbohydrate synthesis
-vascular bundle- where water and food move
1. Starts in the spongy mesophyll
2. CO2 and phosphenolpyruvate (PEP) with help of PEPCO makes oxaloacetate (4C)
3. Oxaloacetate forms malate
4. Malate is taken to the bundle sheath to turn into pyruvate, releasing CO2
5. CO2 goes to C3 cycle and pyruvate goes back to PEP
Process of C4 photosynthesis
Concentration of CO2 is increased about 80 times
When CO2 in released to go to C3 cycle, how does the concentration change?
Compartments that the reactions are separated into in C4 photosynthesis
-night: open- use PEPCO
-day: closed- use rubisco
When are stomates open and closed in CAM photosynthesis?
They lose less water when it is cool
Why do plants in CAM photosynthesis only open stomates at night?
1. Stomate opens at night
2. CO2 and phosphenolpyruvate (PEP) using PEPCO to become oxaloacetate
3. Oxaloacetate becomes malate which is stored in vacuole
4. Stomate closes during the day
5. Malate is released to become pyruvate releasing CO2
6. CO2 goes to the C3 cycle
Process of CAM photosynthesis
-malate storage limited to vacuole so it is limited CO2 therefore can only make so much sugar
-malate may be lost in other processes such as the citric acid cycle
-photorespiration is still a problem
How is CAM photosynthesis inefficient?
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