Who was/were the first to propose that cell membranes are
phospholipid bilayers?
A) H. Davson and J. Danielli
B) I.
Langmuir
C) C. Overton
D) S. Singer and G. Nicolson
E) E. Gorter and F. Grendel
Answer: E
Some regions of the plasma membrane, called lipid rafts, have a
higher concentration of cholesterol molecules. As a result, these
lipid rafts
A) are more fluid than the surrounding membrane.
B) are more rigid than the surrounding membrane.
C) are
able to flip from inside to outside.
D) detach from the plasma
membrane and clog arteries.
E) have higher rates of lateral
diffusion of lipids and proteins into and out of the lipid rafts.
Answer: B
Singer and Nicolson's fluid mosaic model of the membrane proposed
that
A) membranes are a phospholipid bilayer.
B) membranes
are a phospholipid bilayer between two layers of hydrophilic proteins.
C) membranes are a single layer of phospholipids and proteins.
D) membranes consist of protein molecules embedded in a fluid
bilayer of phospholipids.
E) membranes consist of a mosaic of
polysaccharides and proteins.
Answer: D
Which of the following types of molecules are the major structural
components of the cell membrane?
A) phospholipids and cellulose
B) nucleic acids and proteins
C) phospholipids and
proteins
D) proteins and cellulose
E) glycoproteins and cholesterol
Answer: C
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
A) the integral membrane proteins are not strong enough
to hold the bilayer together.
B) water that is present in the
middle of the bilayer freezes and is easily fractured.
C)
hydrophilic interactions between the opposite membrane surfaces are
destroyed on freezing.
D) the carbon-carbon bonds of the
phospholipid tails are easily broken.
E) the hydrophobic
interactions that hold the membrane together are weakest at this point.
Answer: E