Question on cell membranes!?

Question

Which of the following statements about cell membranes is true?

A) Composed of a layer of phospholipids sandwiched between two layers of protein

B) Composed of a double layer of phospholipids interspersed with protein. The polar groups of the phospholipids face each other in the centre of the membrane.

C) Composed of a double layer of phospholipids interspersed with protein. The nonpolar groups of the phospholipids face each other in the centre of the membrane.

D) Composed of a layer of proteins sandwiched between two layers of phospholipids

E) Composed of a double layer of proteins interspersed with phospholipids with the polar groups of the phospholipids facing the nonpolar groups of the proteins.

And no guesses please, I need an explanation!

Answer 1

Cell Membrane: Every cell is enclosed in a membrane, a double layer of phospholipids (lipid bilayer). The exposed heads of the bilayer are "hydrophilic" (water loving), meaning that they are compatible with water both within the cytosol and outside of the cell. However, the hidden tails of the phosopholipids are "hydrophobic" (water fearing), so the cell membrane acts as a protective barrier to the uncontrolled flow of water. The membrane is made more complex by the presence of numerous proteins that are crucial to cell activity. These proteins include receptors for odors, tastes and hormones, as well as pores responsible for the controlled entry and exit of ions like sodium (Na+) potassium (K+), calcium (Ca++) and chloride (Cl-).  

Answer 2

Biology Help

PLANT AND ANIMAL CELL MODELS

http://www.cellbio.com/

http://www.cellsalive.com/

http://www.cellsalive.com/index.htm

http://www.kathimitchell.com/cells.html

http://www.infovisual.info/03/001_en.htm...

http://www.infovisual.info/01/014_en.htm...

http://www.enchantedlearning.com/subject...