1. why do the receptor proteins need to be on the outside of the cell? 2. why can some molecules like water and glucose easily pass through the membrane but macro molecules like starch cannot?

1) receptor proteins need to b on the outside of a cell so the cell can absorb the nutrients it needs. receptors have a specific job, membranes are semi-permeable meaning it doesn't absorb nutrients that are not needed 4 a cell to function in a healthy individual.

2) water and glucose are what most cells need to produce energy to function and produce ATP, which allows the bloodstream to deliver nutrients to the entire body.