The Calvin Cycle

The Calvin Cycle takes place in the Stroma

-The Stroma is the space in the chloroplast

-Kind of like the cytoplasm is the space in the cell, the stroma is the space in the chloroplast

-Do not mix up stroma with stoma (stomata) which are the pores on the leaf

-The Calvin cycle is where the carbon fixation takes place.

-Carbon dioxide is brought into the leaf and the carbon is removed so it can be used in the making of sugar

-The Carbon Dioxide enters the leaf through the stomata. The CO2 diffuses into the chloroplast to take part in the Calvin Cycle.

-The enzyme rubisco takes the CO2 and joins it to RuBP which is a 5 carbon sugar that was already in the chloroplast.

-When the CO2 and RuBP are joined they become PGA a type of 3 carbon sugar. PGA is the building block of G3P which is what the plant wants.

-With the use of ATP, the hydrogens brought by the NADPH are connected to the PGA sugars to form G3P.

-G3P is an important 3 carbon sugar. Two G3P sugars joined together form a glucose sugar molecule.

-The plant can use the G3P sugars to make glucose, fructose, cellulose, starch, or anything else the plant needs.

-The process of the Calvin Cycle produces 6 G3P sugars but only one of them can leave the cycle. The other 5 G3P's will be turned back into RuBP which was used in the beginning of the cycle. The Calvin Cycle must always start with 3 RuBP sugars. This is why it is called a cycle.