Bio chapter 7

Electrogenic pumps

are membrane proteins that generate voltage across a membrane in plants, fungi an bacteria.

Receptor-mediated endocytosis

enables a cell to acquire specific substances from extracellular fluid.

The ideal osmotic environment for a plant cell is a(n) ___ environment.

hypotonic

Passive transport

is the diffusion of a substance across a membrane with no energy investment.

Ligands

molecules that bind specifically to receptor sites, attach to receptor proteins, usually clustered in coated pits on the cell, surface, and are carried into the cell when a vesicle forms.

The plasma membrane is selectively permeable. Which of the following can pass freely through the membrane with no assistance?

oxygen and carbon dioxide

Exocytosis

the cell secretes large molecules by the fusion of vesicles with the plasma membrane.

Osmoreuglation

the control of solute concentrations and water balance.

What drives osmosis?

the difference in water concentration across a selectively permeable membrane

Osmosis

the diffusion of free water across a selectively personnel membrane.

There are two major populations of membrane proteins:

1.Intergral proteins: penetrate the hydrophobic interior of the lipid bilayer. 2. Peripheral proteins: are not embedded in the lipid bilayer at all; they are loosely bound to the surface of the membrane.

Membrane potential

Cells have a membrane potential, a voltage across the plasma membrane due to the unequal distribution of positive and negative ions on either side.

cell-cell recognition

a cell's ability to distinguish one type of neighboring cell from another, it is crucial to the functioning of an organism.

Cotransport

a mechanism through which active transport of a substance is indirectly driven by an ATP-powered pump that transports another solute against its gradient.

Factors that affect membrane fluidity

a) unsaturated vs. saturated hydrocarbon tails. Unsaturated hydrocarbon tails are fluid. b) cholesterol within the animal cell membrane fluidity at moderate temps.

An animal cell placed in a(n) ____ solution will gain water, swell, and possibly burst.

hypotonic

A plant cell surrounded by a(n) ___ solution will be flaccid (limp).

isotonic

What controls the direction of a molecule, such as oxygen, involved in passive transport?

the direction of the oxygen concentration gradient

Which of the following is a difference between active transport and facilitated diffusion?

Active transport involves transport proteins, and facilitated diffusion does not.

fluid mosaic model

Biological membranes consist of various proteins that are attached to or embedded in a bilayer of amphipathic phospholipids.

Plasmolysis

In a hypertonic medium, a plant cell undergoes plasmolysis- that is, the plasma membrane pulls away from the cell wall as water exits and the cell shrivels.

Hypertonic

a hypertonic solution is one with a higher concentration of solutes outside the cell than inside the cell. When a cell is immersed into a hypertonic solution, the tendency is for water to flow out of the cell in order to balance the concentration of the solutes.

Endocytosis

a region of the plasma membrane sinks inward and pinches off to form a vesicle containing material that had been outside the cell.

Isotonic

a solution that when surrounding a cell, causes no net movement of water into or out of the cell.

Hypotonic

a solution that, when surrounding a cell, will cause the cell to take up water.

Stability of an animal cell plasma membrane is enhanced by __________.

cholesterol molecules

A plant cell placed in a(n) ___ solution will lose water and plasmolyze.

hypertonic

There is a net diffusion of water out of an animal cell when it is placed in a(n) ___ solution.

hypertonic

Facilitated diffusion

involves the diffusion of polar molecules and ions across a membrane with the aid of transport proteins, either channel or carrier proteins.

Phagocytosis

is a form of endocytosis in which pseudopodia wrap around a food particle or another large particle, creating a vacuole that then fuses with a lysosome.

Phospholipid

is an amphipathic molecule, meaning it has both a hydrophobic and hydrophillic region.

The ideal osmotic environment for an animal cell is a(n) ____ environment.

isotonic

Active transport

requires the expenditure of energy to transport a solute against its concentration gradient, is essential if a cell is to maintain internal concentrations of small molecules that differ from their concentrations outside the cell.

Plasma membrane

the boundary that separates the living cell from its surroundings and controls traffic into and out of the cell. -the plasma membrane exhibits selective permeability, it allows some substances to cross it easily than others.

Diffusion

the movement of a substance down its concentrations gradient due to random molecular motion (thermal energy)

Tonicity

the tendency of a surrounding solution to cause a cell to gain or lose water.

Some functions of membrane proteins:

transport, enzyme activity, signal transduction, cell-cell recognition,intercellular joining, attachment to the cytoskeleton and extracellular matrix.

Sodium-potassium pump

works this way to exchange N+ and K+ across animal animal cell membranes, creating a higher concentration of potassium ions and lower concentration of sodium ions within the cell.