Can anyone describe the calvin cycle to me?

As complicated as a response to your question would be, I'm answering your question anyway because I have to study this, too, for my upcoming Botany test.

First, the general idea----according to the glossary of my botany textbook the Calvin cycle is given the following description: "The series of enzymatically mediated photosynthetic reactions during which carbon dioxide (CO2) is reduced to 3-phosphoglyceraldehyde (PGA) and the carbon dioxide acceptor, ribulose 1,5-bisphosphate (RuBP), is regenerated. For every three molecules of carbon dioxide entering the cycle, a net gain of one molecule of glyceraldehyde 3-phosphate (PGAL) results."

Now, the details:

The cycle begins when 3 RuBP (15 C in total) are joined with 3 CO2 (3 C in total) coming from the outside, and they form 6 PGA (18 C in total, C conserved). 6 PGA are then reduced into 6 PGAL, converting 6 ATP into 6 ADP and 6 NADPH into 6 NADP+ during the reduction process (ATP and NADPH came from the light reactions). The regeneration of RuBP is needed since RuBP is needed at the beginning of the cycle, so 5 of 6 PGAL (15 C in total) are recombined and rearranged into 3 RuBP (15 C in total, C conserved), converting 3 ATP into 3 ADP during the process (3 ATP came from the light reactions). That 1 extra RuBP gets out of the cycle and is used for systhesis of sugars, starch, amino acids, and fatty acids.

Finally, to summarize:

2 kinds of molecules needed to start the cycle----RuBP and CO2, with CO2 coming from the outside. The two molecules combine to form PGA, then PGA is converted to PGAL, and then the majority of PGAL is used to regenerate RuBP while that one extra PGAL is the net gain of the Calvin cycle that can be used to make other useful stuff. The cycle needs 9 ATP and 6 NADPH from the light reactions.

Hope that helped! What a good review for my test, too----thanks! :)