Ch 06 Lipids, Membranes, and the First Cells First Group

If a solution surrounding a cell is hypotonic relative to the inside of the cell, the water will _______.

move into the cell via osmosis

If a solution surrounding a cell is hypotonic relative to the inside of the cell, the water will _______.

Diffusion

What type of chemical interactions do phospholipids have with their environment?

Amphipathic

Detergents are useful for isolating membrane proteins because __________.

detergents are amphipathic

The three types of lipids found in cells (fats, steroids, and phospholipids) are insoluble in water because they all possess __________.

a significant hydrocarbon component
-Molecules that contain only carbon and hydrogen are known as hydrocarbons. Hydrocarbons are nonpolar because electrons are shared equally in C-H bonds as a result of the approximately equal electronegativity of carbon and hydrogen. Because these bonds form no partial charges, hydrocarbons are hydrophobic.

Lipids are not considered polymers because _________.

they are not composed of monomer subunits.
-There are several different kinds of subunits that may be connected together to form various lipids but because they are not linked into chains, they are not considered monomers.

How does a pump differ from a channel or a carrier?

Pumps require energy for transport, but channels and carriers do not use energy.

Which of the following lipids is classified as a steroid?

Cholesterol

Molecules that move down a concentration gradient and require transport proteins to cross a membrane use __________.

facilitated diffusion

In the illustration, which membrane transport mechanism is best represented by the letter "C"?

Active transport

Which of the following statements best describes the fluid-mosaic model of membrane structure?

The phospholipid bilayer contains diverse proteins, including some embedded amphipathic proteins that span the bilayer.

Which of the following is true of cell membranes?

Amphipathic proteins can span the membrane.

Region A has a low-solute concentration. Region B has a high-solute concentration. They are separated by a selectively permeable membrane that is impermeable to the solute but allows the passage of water. Which of the following is true?

Water moves from region A to region B via osmosis.
-Osmosis occurs only when solutions are separated by a membrane that permits water to cross but holds back some or all of the solutes, that is, a selectively permeable membrane
-The movement of water from region A into region B would help to decrease the high solute concentration in region B, while also increasing the concentration of solutes in region A.

When solutes are diffusing through a membrane from high concentration on one side to low concentration on the other side, what happens when equilibrium is reached?

The rate of diffusion in one direction is the same as the rate of diffusion in the opposite direction.
-At equilibrium, the movement of solutes does not stop. The solutes continue to move back and forth across the membrane.
-At equilibrium, the solute concentrations are the same on either side of the membrane. Therefore, there is nothing to drive the osmosis of water.
-The permeability of the membrane does not change at equilibrium.

Which type of molecule moves across a cell membrane most easily?

Lipid-soluble, nonpolar molecules, such as oxygen and carbon dioxide

The degree of saturation of phospholipids in a membrane will affect which of the following functions of phospholipids?

The permeability of the membrane

In the illustration, which membrane transport mechanism is best represented by the letter "B"?

Facilitated diffusion

Which of the following is true regarding saturated fats?

Saturated fats contain the maximum number of hydrogen atoms that can attach to the carbon skeleton.

Lipid structures vary widely; however, phospholipids and fats are similar in that they both _________.

contain glycerol
-Most phospholipids consist of glycerol linked to only two fatty acids or isoprenoid chains, whereas fats consist of glycerol connected to three fatty acid chains.

Proteins are amphipathic molecules that contain nonpolar (hydrophobic) amino acids and polar (hydrophilic) amino acids. Where would the hydrophobic and hydrophilic amino acid residues of a transmembrane protein be found?

The hydrophobic amino acids would come into contact with the hydrocarbon tails of the phospholipid bilayer, whereas the hydrophilic amino acids would interact with the polar phospholipid heads and the intracellular and extracellular environments.

Which of the following substances is an unsaturated lipid?

Safflower oil

How does the sodium-potassium pump work to transport sodium and potassium against their concentration gradients?

Adenosine triphosphate (ATP) hydrolysis provides the energy to transport ions against their concentration gradients.