AP Biology Unit 2

The LDL receptor is an integral membrane protein that crosses the plasma membrane, with portions of the protein extending both outside and into the interior of the cell. The amino acid side chains (R groups) in the region of the protein that crosses the membrane are most likely

• charged

• hydrophilic

• hydrophobic

• carbohydrates

The hydrophilic regions of a membrane protein are most likely

• present only in muscle cells

• associated with the fatty acid region of the lipids

• either on the surface or inserted into the interior of the membrane

• exposed on the surface of the membrane

Plasma membranes are relatively impermeable to water-soluble molecules because

• the membranes are waxy

• water molecules are nonpolar

• their bilayer is comprised of phospholipids

• they have salt crystals embedded within them

Which of the following is not one of the functional roles of membrane proteins?

• Allowing movement of molecules that otherwise would be excluded by the lipid components of the membrane

• Transferring signals from outside the cell to inside the cell

• Facilitating the transport of macromolecules across the membrane

• Stabilizing the lipid bilayer

Define plasma membrane

• lipid that helps minimize effects of temperature

• only on the outer surface of the plasma membrane and are attached to proteins or lipids; form distinctive cellular markers

• flexible boundary of a cell that separates a cell from its surroundings

• may extend partway into the plasma membrane, cross the membrane entirely, or be loosely attached to its inside or outside face

Which type of biological macromolecule is the main component of the plasma membrane?

• carbohydrate

• lipid

• protein

• nucleic acid

This image is an example of a phospholipid. Which part of a phospholipid is HYDROPHOBIC?

• the phosphate "head"

• the lipid "tails"

This image is an example of a phospholipid. Which part of a phospholipid is HYDROPHILIC?

• the phosphate "head"

• the lipid "tails"

Where can carbohydrates be found when part of a plasma membrane?

• On the outside of the membrane

• On the inside of the membrane

• Embedded part of the way into the membrane

• Embedded the whole way through the membrane

• All of the above

Where can PROTEINS be found when part of a plasma membrane?

• On the outside of the membrane

• On the inside of the membrane

• Embedded part of the way into the membrane

• Embedded the whole way through the membrane

• All of the above