CH - 5 BIOLOGICAL MEMBRANES

AMPHIPATHIC MOLECULE

a molecule containing both hydrophobic and hydrophilic regions

INTEGRAL MEMBRANE PROTEINS

amphipathic proteins firmly bound to the membrane

TRANSMEMBRANE PROTEINS

integral proteins that extend completely through the membrane

PERIPHERAL PROTEINS

inner or outer surface of the membrane

FUNCTION OF MEMBRANE PROTEINS

anchor, transport, enzymatic activity, signal transduction, cell-cell recognition

ANCHOR

\______ the cell to its substrate

TRANSPORT

\______ molecules across the membrane

CATALYZE

\______ enzymatic reactions near cell surface

RECEIVE INFORMATION

\______ from other cells

CELL RECOGNITION

some proteins function as identification tags

PERMEABLE

most \______ to small non polar molecules

WATER

\_____ small enough to pass through bilayer

IMPERMEABLE

\______ to charged ions and most large polar molecules

GASES: N2 , O2, CO2

permeant

HYDROPHOBIC/NONPOLAR MOLECULES

permeant

SMALL POLAR MOLECULES

permeant

LARGE POLAR MOLECULES

not permeant

IONS

not permeant

2 TYPES OF TRANSPORT PROTEINS

channel & carrier

CARRIER PROTEINS

change shape and transfer the molecule

CARRIER-MEDIATED TRANSPORT

transfer of solutes by active or passive transport

ABC TRANSPORTERS

use energy from ATP to transport ions, sugars and polypeptides

CHANNEL PROTEINS

from tunnels/pores through the membrane

(passive transport [diffusion] of water & ions)

PORINS

transmembrane channel proteins that allow solutes or water to pass

AQUAPORINS

gated water channels (allow rapid transport of water)

DIFFUSION

the net movement of particles from an area of high concentration to low concentration

SIMPLE DIFFUSION

small, nonpolar move down the concentration gradient

FACILITATED DIFFUSION

specific protein makes membrane permeable to specific ion or polar molecule

CHANNEL PROTEIN

\______ form hydrophilic channels

OSMOSIS

net movement of water through a selectively permeable membrane

OSMOTIC PRESSURE

the external pressure that must be applied to stop osmosis

ISOTONIC SOLUTION

no net movement of water

HYPERTONIC SOLUTION

higher concentration of solutes outside the cell (cell shrinks)

HYPOTONIC SOLUTION

low concentration of solutes outside the cell (cell swells)

ACTIVE TRANSPORT

the movement of materials through a cell membrane using energy

INDIRECT ACTIVE TRANSPORT

concentration gradient that provides energy for the co-transport of another substance

UNIPORTERS

transport one type of substance [ex : proton pumps]

SYMPORTERS

transport two different substances in the same direction

ANTIPORTERS

move two molecules in opposite directions

EXOCYTOSIS

vesicles fuse with the plasma membrane to move molecules out

PHAGOCYTOSIS

fold plasma membrane to enclose cell/food particle

PINOCYTOSIS

cell takes in liquid from the surrounding environment

RECEPTOR-MEDIATED ENDOCYTOSIS

specific molecules combine with receptor proteins in the membrane

JUNCTIONS

connect cells that form strong connections preventing passage of materials

2 TYPES OF ANCHORING JUNCTIONS

desmosomes & adhering junctions

DESMOSOMES

hold cells together at one spot

ADHERING JUNCTION

cement cells together

TIGHT JUNCTIONS

no space between the cells

GAP JUNCTIONS

allow transfer of small molecules and ions between adjacent cells

PLASMODEMATA

channels that pass through the cells walls of adjacent plant cells