Which two factors of a molecule determine whether or not it can cross the membrane?

Charge & Size

Explanation:

The smaller the particles, the easier they can diffuse through the cell membrane because they can pass through the channels of the cell membrane,

The lipid layer of the cell membrane  is hydrophobic hence‘hates’ charged molecules. Polar or charged molecules will need special channels with trans-membrane proteins to facilitate their movement

its like this, "if i give a plant an unlimited amount of sunlight,then the plant will grow to its largest possible size."

hope it let me know if it does or doesn't =^-^=