Plasma Membrane

Plasma membranes are selectively permeable. This means

• anything can pass in and out

• the membrane regulates the passage of the material in and out of the cell

• glucose cannot enter the cell

• cholesterol cannot enter

Which is NOT a function of the membrane?

• it forms a selective barrier

• it has receptors for chemical messages

• it is the control center of the cell

• it is involved in self recognition

Small, nonpolar, hydrophobic molecules such as fatty acids

• easily pass through the membrane's bilayer

• very slowly diffuse through the bilayer

• require transport proteins

• enter through endocytosis

Which of the following substances would have the most trouble crossing the membrane by diffusing through the bilayer?

• water

• oxygen

• carbon dioxide

• a sodium ion

The cholesterol associated with membranes

• is attached to proteins and extends into the environment surrounding the cell

• helps to add fluidity to the membrane

• is an abnormality resulting from a diet high in cholesterol

• makes the membrane stronger

A major function of glycoproteins and glycolipids in the membane is to

• glue cells together to form tissues

• allow cells to identify each other

• attach membrane to cytoskeleton

• help retain shape

What kinds of molecules pass through a cell membrane most easily?

• ionic

• small and hydrophobic

• large polar

• large and hydrophobic

How would charged ions or water molecules pass into a cell from high to low concentration?

• through a protein channel

• directly through the bilayer

• through a pump using energy

• through facilitated diffusion

Which structure is the hydrophilic polar head of the phospholipid molecule?

• F

• D

• C

• A1

Which structure is the hydrophobic tail of the phospholipid molecule?

• E

• B

• G

• A2