BIO 101 WEEK 5

Water passes quickly through cell membranes because

It moves through aquaporins in the membrane

In the years since the proposal of the fluid mosaic model, what observation has been added to the model?

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

What would tend to increase membrane fluidity?

A greater proportion of unsaturated phospholipids

In order for a protein to be an integral membrane protein, it would have to be

Amphipathic, with at least one hydrophobic region

What would likely move through the bilayer of a plasma membrane most rapidly? Starch, amino acid, K+, CO2, or glucose?

CO2

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

Cell-cell recognition

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by

Cotransport proteins

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

Embedded in a lipid bilayer

The presence of cholesterol in the plasma membranes of some animals

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

Cell membranes of Antarctic ice fish might have what adaptation?

High percentage of polyunsaturated fatty acids

Celery stalks that are immersed in water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are

Hypertonic to fresh water but hypotonic to the salt solution

What is a characteristic feature of a carrier protein in a plasma membrane?

It exhibits a specificity for a particular type of molecule

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in

Lysosomes

What is the voltage across a membrane called?

Membrane potential

What process includes diffusion of a solute across a membrane, transport of an ion down its electrochemical gradient, osmosis and facilitated diffusion?

Passive transport

White blood cells engulf bacteria through what process?

Phagocytosis

What type of molecules are the major structural components of the cell membrane?

Phospholipids and proteins

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. What would be a factor that determines whether the molecule selectively enters the target cells?

Similarity of the drug molecule to other molecules transported by the target cells

What kinds of molecules pass through a cell membrane most easily?

Small and hydrophobic

In the small airways of the lung, a thin layer of liquid is needed between the epithelial cells and the mucus layer in order for cilia to beat and move the mucus and trapped particles out of the lung. One hypothesis is that the volume of this airway surface liquid is regulated osmotically by transport of sodium and chloride ions across the epithelial cell membrane. How would the lack of a functional chloride channel in CF patients affect sodium ion transport and the volume of the airway surface liquid?

Sodium ion transport will decrease; lower osmotic potential will decrease airway surface liquid volume

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

The hydrophobic interactions that hold the membrane together are weakest at this point

A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water, equal to the volume of the blood lost, is transferred directly into one of his veins. What will be the most probable result of this transfusion?

The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells

A protein that spans the phospholipid bilayer one or more times is a

Transmembrane protein

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

Water will leave the cells, causing them to shrivel and collapse