Steroid hormones (such as estrogen) and glucose are transported across cell-surface membranes by simple diffusion and facilitated diffusion respectively. Compare and contrast these two transport processes.

State what microvilli are in terms of cell-surface membrane structure.

Cholesterol is a hydrophobic lipid molecule. Micelles are key to its absorption. Describe the process by which cholesterol is absorbed from the lumen of the small intestine into the epithelial cells lining the ileum.