Biology Ch 5: Membranes

When phospholipids are placed in water, they spontaneously form which of the following?

A bilayer

The lack of double bonds in phospholipids with saturated fatty acids allow them to pack together tightly, and therefore the membrane is ________ fluid. Kinks introduced by double bonds in lipids with unsaturated fatty acids prevent them from packing together tightly, and therefore the membrane is __________ fluid.

Blank 1: less Blank 2: more

Although a eukaryotic cell membrane can contain many different lipids, they can be classified in three groups: glycerol phospholipids, ______ , and ________ . When answering the question think about the lipids found in membranes, not about all the lipids that an organism makes!

Blank 1: sphingolipids Blank 2: sterols

What type of microscope can be used to see the two phospholipid layers in a plasma membrane, as in this image?

Electron

Which of the following is NOT one of the four main components of all plasma membranes?

Extracellular matrix

Which of the following is not one of the four main components of all plasma membranes?

Extracellular matrix

Which method of microscopy, commonly used to study lipid bilayers, was used to produce this image?

Freeze-fracture microscopy

Identify the four main components of all eukaryotic membranes.

Lipid bilayer Interior protein network Cell surface markers Transmembrane proteins

Which of the following are typical components of biological membranes?

Lipids Proteins

Which of the following makes up the bilayer of every cell membrane?

Phospholipids

Which of the following can relatively easily move laterally within the plasma membrane?

Phospholipids and unanchored proteins

Select the accurate statements concerning membrane fluidity.

Phospholipids are relatively free to move laterally within the membrane. Unanchored proteins are relatively free to move laterally within the membrane.

How does lipid composition affect membrane fluidity?

Saturated fatty acids tend to make the membrane less fluid because they pack together well. Sphingolipids tend to make the membrane less fluid.

Choose the three groups of lipids found in eukaryotic cells.

Sphingolipids Glycerol phospholipids Sterols

When phospholipids are placed in water, they spontaneously form a bilayer. Why?

The polar heads on the surface of the bilayer interact with water, while the nonpolar tails in the interior of the bilayer do not come into contact with water.

Which of the following is a defining feature of biological membranes?

The presence of two phospholipid sheets

In order to survive, grow, and reproduce, a cell must ______.

exchange materials and information with its environment

Cells continually exchange materials and information with their environment. This exchange is crucial ______.

for all the processes occurring in a cell

The lipid bilayer that forms the core of all cell membranes is composed primarily of ____.

phospholipids

Compared to the ER membrane, the plasma membrane contains more ______.

sphingomyelin cholesterol phosphatidylcholine