Animal cells (including humans ofcourse), heterotrophs, derive their energy from coupled oxidation-reduction reactions. Glucose is a primary fuel for heterotrophs. Energy derived from glucose is stored in the form of high-energy phosphate bonds in ATP, or other nucleotide triphosphates, and as energy-rich hydrogen atoms associated with the co-enzymes NADP and NAD .
Glucose is unable to diffuse across the cell membrane without the assistance of transporter proteins. At least 13 hexose transporter proteins with different functions have been identified. Some hexose transporters allow glucose to flow passively from high to low concentration without requiring the expenditure of cell energy. Those that move glucose against its concentration gradient consume energy, generally in the form of ATP.
D-Glucose is the natural form used by animal cells.
Your question is rather unclear but from what I can tell either there were not an even amount of Petri dishes or some of them were left open while others were not.
