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.