Plasma Membrane & transport

Identify cholesterol molecule

• structure i

• structure b

• structure h

• structure a

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

Membrane phospholipids

• have hydrophobic heads that face the center of the membrane and are shielded from water

• have hydrophilic tails that face outward

• remain fluid because they are tightly packed

• none of these

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 stabilize the membrane at body temperature

• is an abnormality resulting from a diet high in cholesterol

• both a and c

The fluid mosaic model describes a membrane consisting of

• a phospholipid bilayer with embedded proteins

• 2 layers of phospholipids with proteins in between

• individual proteins and phospholipids that can drift

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

• ionic

• small and hydrophobic

• large polar

• large and hydrophobic

Which of the following would likely move through the lipid bilayer most rapidly?

• potassium

• an amino acid

• Carbon dioxide

• glucose