BIO1610 Ch.7

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

CO2

Which of the following most accurately describes selective permeability?

Only certain molecules can cross a cell membrane.

In cotransport,

a membrane protein couples the transport of two solutes.

This ---------requires the cell to expend metabolic energy and enables a cell to maintain internal concentrations of small molecules that would otherwise diffuse across the membrane.

active transport

Phospholipids and most other membrane constituents are ---------, which have both hydrophobic and hydrophilic regions.

amphipathic molecules,

The passage of water through the membrane can be greatly facilitated by channel proteins known as

aquaporins.

Peripheral proteins

are not embedded in the lipid bilayer at all. o Instead, peripheral proteins are loosely bound to the surface of the membrane, often to integral proteins.

Membrane carbohydrates are important for

cell-cell recognition.

A single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes in a mechanism called

cotransport.

One result of thermal motion is

diffusion, the movement of molecules of any substance to spread out in the available space.

During ---------, a cell brings in biological molecules and particulate matter by forming new vesicles from the plasma membrane.

endocytosis

In --------, a transport vesicle budded from the Golgi apparatus is moved by the cytoskeleton to the plasma membrane.

exocytosis

Bulk transport across the plasma membrane occurs by

exocytosis and endocytosis

The passive movement of molecules down their concentration gradient with the help of transport proteins is called --------

facilitated diffusion.

If a plant cell and its surroundings are isotonic, there is no movement of water into the cell. The cell becomes --------(limp), and the plant may wilt.

flaccid

Many ion channels function as --------

gated channels.

Some ion pumps

generate voltage across membranes.

If the cell is immersed in a solution that is--------- to the cell (containing nonpenetrating solutes), the cell loses water to its environment, shrivels, and probably dies.

hypertonic

If the cell is immersed in a solution that is--------- to the cell, water enters the cell faster than it leaves, and the cell swells and lyses (bursts) like an overfilled water balloon.

hypotonic

Membranes have distinct

inside and outside faces.

The extracellular matrix is thought to participate in the regulation of animal cell behavior by communicating information from the outside to the inside of the cell via which of the following?

integrins

If a cell without a cell wall, such as an animal cell, is immersed in an environment that is---------to the cell, there is no net movement of water across the plasma membrane.

isotonic

Proteins determine

most of the membrane's specific functions.

Active transport uses energy to

move solutes against their gradients

Particles and large molecules, such as polysaccharides and proteins, cross the membrane via

packaging in vesicles.

Specific proteins facilitate the

passive transport of water and selected solutes.

Integral proteins

penetrate the hydrophobic interior of the lipid bilayer, usually completely spanning the membrane as transmembrane proteins.

There are three types of endocytosis:

phagocytosis ("cellular eating"), pinocytosis ("cellulardrinking"), receptor-mediated endocytosis.

Water diffuses across the membrane from the

region of lower solute concentration (higher free water concentration) to the region of higher solute concentration (lower free water concentration) until the solute concentrations on both sides of the membrane are equal.

The diffusion of a substance across a biological membrane is passive transport because it

requires no energy from the cell to make it happen.

Membrane structure results in

selective permeability

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

small and hydrophobic

The ---------- pump works this way in exchanging sodium ions (Na + ) for potassium ions (K + ) across the plasma membrane of animal cells.

sodium-potassium

Cell membranes are permeable to

specific ions and a variety of polar molecules, which can avoid contact with the lipid bilayer by passing through transport proteins that span the membrane.

Cell survival depends on

the balance between water uptake and loss.

Movement of a molecule through a membrane depends on

the interaction of the molecule with the hydrophobic interior of the membrane.

Osmosis is

the passive transport of water.

Both solute concentration and membrane permeability affect ---------, the ability of a surrounding solution to cause a cell to gain or lose water.

tonicity

In the absence of other forces, a substance diffuses from

where it is more concentrated to where it is less concentrated, down its concentration gradient.

Some transport proteins can move solutes across membranes against their concentration gradient, from the side

where they are less concentrated to the side where they are more concentrated.