Session 6 - Cellular Form and Function

Compared to a typical animal cell, the cell membranes on the paw of a polar bear would most likely have an increased concentration of which macromolecule?

• Potassium channel proteins

• Saturated phospholipids

• Aquaporin proteins

• Unsaturated phospholipids

Which of the following statements concerning lipid bilayers is NOT true?

• Ions are charged, so they cannot move across the hydrophobic region of the lipid bilayer freely.

• Ions (charged particles) can freely move across the lipid bilayer.

• A phospholipid is unique in that it has a hydrophilic region called the head, and a hydrophobic region known as the tail.

• The lipid bilayer is arranged in two layers of phospholipids, with the hydrophilic heads forming the outer edges and the tails forming the interior.

The membrane itself is hydrophobic in the inner layers and doesn't allow water-soluble molecules to pass, yet water itself can permeate cells. Why?

• Channels called aquaporins in the membrane allow water molecules to pass through freely.

• Water molecules cannot pass through the membrane. The water that is inside a cell stays in it throughout its life.

• The membrane is fallible and sometimes water leaks through.

• Sometimes the membrane will mistake water molecules for lipids.

Cholesterol is an important lipid in the phospholipid bilayer, since this steroid is needed to create the animal cell membrane. Which of these describes the function of cholesterol in the cell membrane?

• Communicates with other cells

• Reduces the permeability of the membrane

• Regulates the temperature of the membrane

• All of these

Which of the following statements about the lipid constituents of membranes is correct?

• Lateral movement of membrane lipids is catalyzed by special proteins.

• Transverse movement of membrane lipids within the bilayer is unrestricted.

• Lateral movement of membrane lipids occurs rapidly within the plane of the bilayer.

• The inner and outer halves of the lipid bilayer are identical.

Which of the following statements about membrane proteins is not correct?

• Integral membrane proteins are anchored to the lipid bilayer by ionic bonds.

• Transmembrane porins have hydrophilic amino acids that point inwards in the beta barrels.

• Integral membrane proteins have transmembrane domains rich in hydrophobic amino acids

• Integral membrane proteins have ends rich in hydrophilic amino acids.