Chapter 7 Homework

Exocytosis

secretes large molecules out of the cell increases the surface area of the plasma membrane requires fusion of vesicles with the plasma membrane

When a person is dehydrated, his or her IV fluids

should be isotonic, because either a hypertonic or hypotonic IV would damage red blood cells.

A human cell placed in a hypotonic environment would

take up water through osmosis.

Active and passive transport of solutes across a membrane typically differ in which of the following ways?

Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy.

Extracellular matrix

a fluid protein-carbohydrate matrix that supports the cell.

Which of the following factors would tend to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

If you are going to bake potatoes, and your potatoes are soft and dehydrated, they can be soaked in __________ to make them more firm before baking.

a hypotonic solution such as tap water

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

embedded in a lipid bilayer.

Endocytosis

forms vesicles from inward folding of the plasma membrane decreases the surface area of the plasma membrane

During osmosis, water diffuses across a selectively permeable membrane from the region of higher __________ concentration and lower ____________ concentration to the side with lower ___________ concentration and higher___________concentration.

free water solute free water solute

Paramecium is a genus of protists that lives in water. It has organelles called contractile vacuoles that continually eliminate the excess water gained through osmosis. Knowing that Paramecia gain water through osmosis, we can deduce that they normally live in

freshwater lakes and ponds.

The sodium-potassium pump is called an electrogenic pump because it ________.

generates voltage across the membrane

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements.

1. The diverse proteins found in and attached to membranes perform many important functions. 2. Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane. 3. The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center

Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?

It exhibits specificity for a particular type of molecule.

The force driving simple diffusion is ________, while the energy source for active transport is ________.

a concentration gradient; ATP hydrolysis

Which of the following statements correctly describes the effect the sodium-potassium pump has on the concentrations of Na+ and K+ across the plasma membrane?

The concentration of Na+ is greater outside the cell, and the concentration of K+ is greater inside the cell.

Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels? Select all that apply.

The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane. The diffusion of K+ ions out of the cell is impeded by the electrical gradient across the plasma membrane. The electrochemical gradient is larger for Na+ than for K+. For Na+ ions, diffusion through the Na+ channel is driven by both the concentration gradient and the electrical gradient. But for K+ ions, the electrical gradient opposes the concentration gradient. Therefore, the electrochemical gradient for Na+ is greater than the electrochemical gradient for K+.

Which of the following statements correctly describes the effect the sodium-potassium pump has on the distribution of charge across the plasma membrane?

The outside of the cell is more positive than the inside because more positive ions are pumped out of the cell than are pumped in

Integral Membrane Protein

a type of membrane protein that is permanently attached to the biological membrane.

For a protein to be an integral membrane protein, it would have to be _____.

amphipathic, with at least one hydrophobic region

A cell that neither gains nor loses water while sitting in a solution is probably sitting in

an isotonic environment.

The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following?

cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis Movement of most solutes against their concentration gradient couples the movement of one solute down its concentration gradient to the movement of another (glucose in this case) against its concentration gradient.

Which of the following is least likely to be important in holding the components of a biological membrane together?

covalent interactions between the phospholipid and protein components of the membrane This is not an important interaction because there are rarely covalent bonds between the phospholipids and integral membrane proteins.

A human cell placed into a hypertonic solution is likely to

lose water by osmosis.

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

Facilitated diffusion is a type of _______.

passive transport During facilitated diffusion, the cell is not expending energy to move the particles across the membrane; therefore, facilitated diffusion is a form of passive transport.

A white blood cell engulfing a bacterium is an example of _____.

phagocytosis

Endocytosis and exocytosis

requires cellular energy transported substances never physically cross the plasma membrane

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

small and hydrophobic

Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane?

small ions

Many bacteria and fungi have a difficult time surviving on our food if the food is very salty. The best explanation for this is

that the salt in the food creates a hypertonic environment for the bacteria and fungi.

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid

Cotransport

the energy available from an ion moving through a transport protein down its electrochemical gradient is coupled with the movement of another solute (small polar molecule or ion) through the same protein but against its concentration or electrochemical gradient. The solute that is being transported against its gradient may move into the cell or out of the cell (but not both), depending on the type of transport protein that catalyzes this process.

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

the similarity of the drug molecule to other molecules that are transported into the target cells If the target cells have transport proteins that specifically bind to certain molecules, they may bind with and transport a drug that is similar in structure.

The permeability of a biological membrane to a specific polar solute depends primarily on which of the following?

the types of transport proteins in the membrane The lipid bilayer will be impermeable or very poorly permeable to polar or charged solutes. The presence of the correct transport protein will determine the permeability.

Which of the following best describes the structure of a biological membrane?

two layers of phospholipids with proteins either crossing the layers or on the surface of the