Bulk Transport

Free Response

Why is it important that there are different types of proteins in plasma membranes for the transport of materials into and out of a cell?

Hint:

The proteins allow a cell to select what compound will be transported, meeting the needs of the cell and not bringing in anything else.

Why do ions have a difficult time getting through plasma membranes despite their small size?

Hint:

Ions are charged, and consequently, they are hydrophilic and cannot associate with the lipid portion of the membrane. Ions must be transported by carrier proteins or ion channels.