AP BIO 2.2

Who was/were the first to propose that cell membranes are phospholipid bilayers?

E) E. Gorter and F. Grendel

Who proposed that membranes are a phospholipid bilayer between two layers of hydrophilic proteins?

A) H. Davson and J. Danielli

Who proposed that the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids?

D) S. Singer and G. Nicolson

Which of the following types of molecules are the major structural components of the cell membrane?

C) phospholipids and proteins

peripheral protein

D

cholesterol

E

fiber of the extracellular matrix

A

microfilament of the cytoskeleton

C

glycolipid

B

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that

E) the hydrophobic interactions that hold the membrane together are weakest at this point.

The presence of cholesterol in the plasma membranes of some animals

A) enables the membrane to stay fluid more easily when cell temperature drops

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

A) They can move laterally along the plane of the membrane

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?

A) by increasing the percentage of unsaturated phospholipids in the membrane

In order for a protein to be an integral membrane protein it would have to be which of the following?

C) amphipathic

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

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

A) The double bonds form kinks in the fatty acid tails, forcing adjacent lipids to be further apart

Which of the following is true of integral membrane proteins?

C) They are usually transmembrane proteins

Of the following functions, which is most important for the glycoproteins and glycolipids of animal cell membranes?

E) a cell's ability to distinguish one type of neighboring cell from another

An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function?

B) cell-cell recognition

In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?

D) The concentration of protein molecules is now known to be much higher

21) Which of the following span the phospholipids bilayer, usually a number of times?

A) transmembrane proteins

Which of these are not embedded in the lipid bilayer at all?

C) peripheral proteins

Which of these are attached to the extracellular matrix?

D) integrins

Which of these often serve as receptors or cell recognition molecules on cell surfaces?