Chapter 5: Membrane Dynamics

composed of a phospholipids bilayer, hydrophilic phosphate heads and a hydrophobic tail, cholesterol molecules that help stabilize the cell membrane (tooth pick)

receive and transmit messages into the cell

form specialized doorways for specific molecules

(desmosomes or gap junctions) that allow the cells to stick to each other and allow small molecules to move between the cytoplasm of adjacent cells

the cell-cell junctions act as barriers to minimize the unregulated diffusion of material between cells, so there is very little paracellular transport

(cells that line the small intestine)

antigen (cell marker) identify self to self

osmosis

filtration

facilitated diffusion

diffusion

diffusion of water using kinetic energy (H2O follows solute)

moves from high to lower concentration (moving out of an airport)

uses hydrostatic pressure

moves from higher to lower concentration with the aid of a transporter faster movement using kinetic energy

describes a solution and how that solution affects cell volume (H2O follows solute)

cell swells when placed in solution and therefor gains water

cell shrinks when placed in solution and therefore loses water

cell neither gains or loses water when placed in solution

moves substances from higher concentration to an area of lower concentration

how it moves out of membrane

utilize membrane-spanning protein subunits with a tunnel or pore which is open at both ends at the same time

utilize membrane-spanning protein subunits that bind to the substrates that they carry, but never form a direct connection between the intracellular and extracellular fluids

(revolving door)

active transport (direct/indirect)

endocytosis

exocytosis

moving substances against the concentration gradient, selectively permeable

sodium - outside

potassium - inside

low to high concentration

the energy to push molecules against the concentration gradient comes directly from the high-energy phosphate bond of ATP

uses the kinetic energy in one molecule moving down its concentration gradient to push other molecules against their concentration gradient

into the cell - an indentation by the membrane, surround and pinched off and moved to where it will be digested in a much smaller vesicle

pinocytosis, phagocytosis, receptor mediated

cell eating (going after it) using a large membrane-bound vesicle

cell drinking

active mediated transport

out of the cell - enclosed by the membrane in a vesicle and transported out of the cell thus rupturing outside the cell (secretion)

the ability of a carrier to move only one molecule or only a group of closely related molecules

where a transporter may move several members of a related group of substrates, but those substrates will compete with one another for the binding sites on the transporter

depends on both the substrate concentration and the number of carrier molecules

movement occurs through the junctions between adjacent cells

(plasma, interstitial fluid of GI tract)

movement occurs through the epithelial cells themselves forcing the crossing of two cell membranes

(alveoli and blood)

allow small molecules and ions to move between the cytoplasm of adjacent cells

(muscle cells of the heart and digestive tract)

attach the intermediate filaments of the cytoskeleton. strongest of the cell-cell anchoring junctions

(muscles of the heart)

the substance is enclosed in a membranous vesicle which fuses with the plasma membrane and ruptures. releasing the substance to the exterior

existing body load + [intake/metabolic production] - [excretion/metabolic removal]

rate at which molecule disappears from the body

mass flow = concentration x volume flow