Lipid Bilayer

A molecule that has both a hydrophilic and a hydrophobic part is called an amphipathic molecule.

• True

• False

The cell membrane is composed of a phospholipid bilayer. Is the outside of the membrane hydrophilic or hydrophobic?

• Hydrophobic

• Hydrophilic

According to the fluid mosaic model of cell membranes, which type of molecule spans the membrane, from its inner to outer surface?

• Cholesterol

• A single phospholipid

• Integral protein

• Peripheral protein

Which statement describes the function of cholesterol in membranes?

• Makes the membrane more flexible at high temperatures.

• Enables the membrane to stay fluid more easily when cell temperature drops.

• Enables the membrane to remove hydrogen atoms from saturated phospholipids.

• Enables the membrane to add hydrogen atoms to unsaturated phospholipids.

Which of the following statements correctly describe the Davson–Danielli model?

• It comprises a lipid bilayer.

• It comprises a lipid bilayer coated by a protein layer on the side of the membrane facing inside the cell.

• It comprises a lipid bilayer sandwiched between two protein layers on either side of the membrane.

• It comprises a lipid bilayer coated by a protein layer on the side of the membrane facing outside the cell.

Which of the following molecules are amphipathic?

• cholesterol, phospholipids, integral proteins, peripheral proteins

• Integral proteins only

• cholesterol, phospholipids, integral proteins

• Peripheral proteins only

• c.

• d.

• b.

• a.

What is the key difference between integral and peripheral proteins?

• Integral proteins are just cooler

• Peripheral proteins extend through the entire membrane, whilst integral proteins don't

• Integral proteins extend through the entire membrane, whilst peripheral proteins don't

• There is no key difference between the two

When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are:

• Integral proteins

• Carbohydrates

• Phospholipids

• Peripheral proteins

Which of the following is a more accurate representation of the cell membrane?

• Left Diagram

• Right Diagram