MasteringBio: Cell Membranes

Which of the following is a major cause of the size limits for certain types of cells?

the need for a surface area of sufficient area to allow the cell's function

What is the function of Structure E?

stabilization of the phospholipids - (Cholesterol helps to stabilize the structure of the plasma membrane.)

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

True - (The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail.)

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

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

What name is given to the process shown in this animation?

diffusion - (Diffusion is the movement of particles down their concentration gradient.)

Identify Structure D.

phospholipid bilayer of membrane - (Phospholipids can be recognized by the presence of a head and two tails.)

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature - (Detergents form micelles around the grease, which are then washed away because the polar head groups facing outward on the micelle are water-soluble.)

Which of the following is true of the evolution of cell membranes?

As populations of organisms evolve, different properties of their cell membranes are selected for or against.

Which of these cannot rapidly pass directly through the phospholipids of the plasma membrane?

B, C, and D - (Water, Glucose, and Hydrogen) - (Ions, such as hydrogen ions, and hydrophilic molecules, such as water and glucose, cannot rapidly pass directly through the phospholipids of a plasma membrane. To move rapidly through the membrane, they must pass through membrane transport proteins.)

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

Hypotonic - (The salt concentration in the solution is lower than it is in the cell, so water enters the cell, causing it to burst.)

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar. - (Lipids are nonpolar molecules, whereas sugars are polar.)

Which of the following particles could diffuse easily through a cell membrane?

Oxygen (O2) - (Small nonpolar molecules such as oxygen can diffuse across cell membranes.)

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

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

Which of the following factors does not affect membrane permeability?

The polarity of membrane phospholipids - (Phospholipids contain both a polar head and a nonpolar hydrocarbon tail, both of which are necessary for their ability to form membrane bilayers.)

True or false? Osmosis is a type of diffusion.

True - (Osmosis is the diffusion of water across a selectively permeable membrane.)

Identify Structure A.

glycoprotein - (Structure A is composed of both a carbohydrate and a protein)

Water passes quickly through cell membranes because

it moves through aquaporins in the membrane.

Structure A in this animation is a(n) _____.

transport protein - (The protein is allowing solute molecules to enter the cell.)