Q: What cellular mechanism causes cancer? Select one:
a. cells produced with no DNA
b. uncontrolled cell division
c. defective cell membranes
d. cells produced without nuclei

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?