Looks like no one added any tags here yet for you.
calvin cycle
the light-independent (dark) reactions of photosynthesis that take place in the storm of the chloroplast
Three phases:
Carbon Fixation
Reduction
Regeneration of RuBP
Carbon fixation
first phase of the Calvin Cycle; a single chemical reaction that produces two three-carbon molecules (3-PG) from 1 CO2 molecule combining 1 five-carbon molecule (RuBP)
Ribulose-1,5,-bisphosphate (RuBP) combines with CO2 to produce an unstable six-carbon intermediate that ultimately splits into two 3-phosphoglycerate molecules.
must take place minimum 3x to produce one G3P molecule used in glucose synthesis.
Reduction
the second phase of the Calvin Cycle; two redox chemical reactions that produce glyceraldehyde-3-phosphate (G3P)
required minimum 2 G3P molecules
One G3P molecule is producedÂ
One ATP molecule is usedÂ
One NADPH molecule is oxidized
Regeneration of RuBP
the third phase of the Calvin Cycle; two chemical reactions that utilize some of the G3Pproduced to reproduce RuBP (other molecules outside of the Calvin Cycle are used to produce glucose
requires minimum 2 G3P molecules to regenerate 1 RuBP molecule, allowing the cycle to continue
mycorrhizae
a class of fungi that forms symbiotic relationships with many plant species; found beneath the soil among plant roots
excellent at carbon sequestration, sequestering carbon from the atmosphere and soil, which is provided to the plant host to aid in light-independent reactions of photosynthesis
photorespiration
a process that occurs in plants when the enzyme RuBisCO oxygenates RuBP instead of carboxylating it, leading to a decrease in photosynthetic efficiency
wasteful because it used energy produced form the light-independent reactions
the cell also has to expend energy to clean up the mess from photorespiration
transpiration
process of plants in exchanging gases (specifically, O2 and CO2), as well as release H2O through small pores located on the underside of their leaves called stomata (plural of stoma
occurs in C3 plants; stroma will open if:
High humidityÂ
Heat (often a result of direct sunlight)Â
Low atmospheric CO2 concentrations
C3 plants lack mechanisms for mitigating photorespiration
spatial and temporal mechanisms for reducing the likelihood of photorespiration occurring
since the Calvin Cycle in C3 plants takes place in leaf cells known as mesophyll, if the stomata of the leaves are open and gas exchange can occur, CO2 and O2 can enter/ exit the leaf, meaning that the Calvin Cycle and photorespiration are possible.Â
C4 plants have a spatial mechanism to mitigate photorespiration
helps prevent CO2 loss via stomata, which augments overall concentration of CO2 for carbon fixation of the Calvin Cycle
the enzyme PEP carboxylase catalyze the reaction of producing oxaloacetate from phosphoenolpyruvate (PEP) and incoming CO2
Oxaloacetate is then converted to malate and transported into another cell type, bundle sheath cells, where the Calvin Cycle can take place.Â
Pyruvate is also produced from the catabolism of malate, and this pyruvate can then be recycled to reproduce PEP.
CAM plants employ temporal mechanism to mitigate photorespiration
generally desert/tropical plants; have a temporal mechanism to reduce CO2 loss via stomata
During daytime, the stomata are closed and CO2 (accumulated over the course of the night) can be fixed in the Calvin Cycle.Â
During nighttime, the stomata are open and PEP carboxylase catalyzes the same reaction observed in the mesophyll cells of C4 plants to accumulate more CO2 for carbon fixation during the day.