Which of the following gives you information about population density? A
the number of births per year

B
the number of frogs in a pond

C
the number of deaths per year

D
the number of bacteria per square millimeter

Molecules like glucose and amino acids are not lipid soluble, so cannot cross the cell membrane by simple diffusion. instead, they are shuttled across by carrier proteins in the membrane from high to low concentration. does this process require energy from the cell? this is an example of what type of molecular movement?