Mastering Biology Chapter 7 q+a's

Some solutes pass readily through the lipid bilayer of a cell membrane, whereas others pass through much more slowly, or not at all.

-Small nonpolar (hydrophobic) molecules, such as dissolved gases (O2, CO2, N2) and small lipids, can pass directly through the membrane. They do so by interacting directly with the hydrophobic interior of the lipid bilayer. -Very small polar molecules such as water and glycerol can pass directly through the membrane, but much more slowly than small nonpolar molecules. The mechanism that permits small polar molecules to cross the hydrophobic interior of the lipid bilayer is not completely understood, but it must involve the molecules squeezing between the hydrophobic tails of the lipids that make up the bilayer. -Polar molecules such as glucose and sucrose have very limited permeability. -Large molecules such as proteins cannot pass through the lipid bilayer. -Ions and charged molecules of any size are essentially impermeable to the lipid bilayer because they are much more soluble in water than in the interior of the membrane.

Which of the following membrane activities requires energy from ATP hydrolysis?

Na+ ions moving out of the cell

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid

Which of the following statements is TRUE with regard to this animation?

Both sodium and potassium ions are transported against their concentration gradients.

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

Certain proteins are unique to each membrane.

Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following types of treatments?

Hydrating drinks that include high concentrations of salts and glucose

Which of the following statements correctly describes osmosis?

In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.

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

Phagocytosis

When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane?

There is random movement of substances into and out of the cell.

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

cell-cell recognition

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

Facilitated diffusion is a type of _______.

passive transport

An organism with a cell wall would most likely be unable to take in materials through _____.

phagocytosis

The difference between pinocytosis and receptor-mediated endocytosis is that _____.

pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity

Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply.

water, oxygen, carbon dioxide, lipids