IB Biology 1.3

What special property of phospholipid molecules explains their ability to spontaneously assemble into a lipid bilayer?

• A. They are hydrophobic.

• B. They are amphipathic.

• C. They are saturated.

• D. They are hydrophilic.

Which statement applies to cholesterol?

• A. It is hydrophobic and found on the outside of the phospholipid bilayer.

• B. It is hydrophilic and found inside the phospholipid bilayer.

• C. It impacts membrane fluidity.

• D. It is transported in association with glucose in the blood.

The Davson–Danielli model of membrane structure proposed that membranes were composed of a phospholipid bilayer that lies between two layers of globular proteins, as shown in this diagram.

The Davson–Danielli model of membrane structure proposed that membranes were composed of a phospholipid bilayer that lies between two layers of globular proteins, as shown in this diagram.

• A. An electron micrograph that showed two dark lines with a lighter band in between

• B. Freeze-fracture electron microscopy

• C. Evidence that all membranes are identical

• D. The hydrophobic regions of protein would be in contact with water.

A diagram of a membrane

• A

• B

• C

• D

A diagram of a membrane

In the diagram, which structure is an intrinsic or integral protein?

• A.

• B.

• C.

• D.

The cell membrane model proposed by Davson–Danielli was a phospholipid bilayer sandwiched between two layers of globular protein.  Which evidence led to the acceptance of the Singer–Nicolson model?

• A. The orientation of the hydrophilic phospholipid heads towards the proteins

• B. The formation of a hydrophobic region on the surface of the membrane

• C. The placement of integral and peripheral proteins in the membrane

• D. The interactions due to amphipathic properties of phospholipids

What are the parts of the cell membrane indicated in the diagram?

• A.

• B.

• C.

• D.

A number of different proteins are involved in nerve function. Which of the following does not require a membrane protein?

• A. Active transport of sodium

• B. Diffusion of K⁺ into the cell

• C. Diffusion of the neurotransmitter across the synapse

• D. Binding of the neurotransmitter to the post-synaptic membrane

What is the approximate thickness of the plasma membrane of a cell?

• A. 10 nm

• B. 50 nm

• C. 10 µm

• D. 50 µm

Which process is possible due to the fluidity of cell membranes?

• A. Endocytosis

• B. Osmosis

• C. ATP production

• D. Cell recognition