Module 1.4: Movement Through the Cell Membrane Flashcards
Selective permeability is
characterized by the ability of certain substances to pass through the cell membrane while other molecules cannot.
Solute is
the substance being dissolved into another substance
Passive transport occurs
when substances move through the membrane without the input of energy.
Simple diffusion
best-known passive process
is the tendency for solutes (ions and molecules) to move from an area of high concentration to an area of lower concentration.
The concentration gradient refers to
the gradual change in the observed concentration of solutions present between two areas.
Osmosis
is the passive diffusion of water (or other solvents) through a selectively permeable membrane.
Isotonic
refers to having an equal amount of solute on either side of a membrane.
Hypertonic
(the prefix hyper means “above”) solutions contain more solute particles relative to another solution.
Hypotonic
(the prefix hypo means “below”) solutions contain fewer solute particles relative to another solution.
Filtration
is the movement of fluid through a filtration membrane or small space that contains small openings.
Facilitated diffusion
is the diffusion of lipid-insoluble molecules across a membrane.
Carrier mediated transport occurs
when a **channel protein **spans the membrane, creating a tunnel like structure that allows specific molecules to pass through via diffusion.
Channel proteins allow polar and charged molecules to bypass the hydrophobic region of the membrane and enter the cytoplasm of the cell.
Carrier proteins are
Another example of facilitated diffusion
Active transport
occurs when an input of energy is required to move substances through the membrane.
The sodium-potassium pump
is an active form of transport used to move sodium ions out of (and potassium ions into) the cell.
Secondary active transport
occurs when one molecule, such as sodium, is transported across the membrane thereby providing energy for a second substance, such as glucose, to be transported across the cell membrane.
Cotransport is when
the diffusing substance (glucose) moves in the same direction as the transported substance (sodium)
Counter transport is
when the diffusing substance moves in the opposite direction as the transported substance (opposite of cotransport)
Vesicles
are small membrane-bound organelles used to transport materials within, out of or into a cell.
Exocytosis
- (exo- means “going out”)
- requires energy
*
Endocytosis
(the prefix endo means “bringing in”) occurs when a macromolecule outside of the cell is enclosed by a portion of the cell membrane (forming a vesicle) and is transported inside the cell through an energy dependent process.
Receptor mediated endocytosis (RME)
involves receptors on the cell membrane binding with specific molecules outside of the cell.
Ligands
These external molecules
Phagocytosis
is the endocytosis of extremely large objects.
Phagosomes
The vesicles formed during phagocytosis
Pinocytosis
is the endocytosis of tiny droplets of fluids.
Electrical gradients arise from
the electrical charge of the cellular environment created by the repulsion of like charges and the attraction of opposite charges of ions within the environment.
This combination of electrical gradients and concentration gradients is called the
electrochemical gradient
Membrane channels may be
voltage gated— meaning the electrical potential within the membrane determines whether these channels are open or closed.
The resting membrane potential is
when the cell and its extracellular environment are in chemical and electrical equilibrium.
Depolarization
a shift in the internal charge to a less negative state
