2.4 Transport Across Membranes

Diffusion

Movement of substance from an area of high concentration to low concentration

Dynamic Equilibrium

state at which there is uniform distribution and zero not movement of particles

faster rate of diffusion

Large difference → Large gradient → ____________

Permeability

ability of membrane to allow particles through

Permeable

allows particles through

Semipermeable

selectively permeable, cell membranes

Impermeable

allows no particles through

Passive Transport

Movement of material across a cell membrane along its concentration gradient without the expenditure of energy (no ATP), (high -> low)

Active Transport

movement of substances across the cell membrane AGAINST their concentration gradient (low -> high)

Bulk Transport

large molecules across the membrane with the help of vesicles made with membrane

Simple Diffusion

unassisted movement of small, non-polar molecules. O2, CO2, N2, Glycerol

Facilitated diffusion

Assisted movement of molecules by transport proteins

Osmosis

Diffusion of WATER across semipermeable membrane

Primary Active Transport

movement of substances AGAINST gradient (low → high), requires ATP, uses pumps / transport proteins

Secondary Active Transport

movement of substances AGAINST gradient (low → high), requires (ATP→ ADP), driving ion + secondary ion

Excocytosis

Removal of materials from cytosol to ECF (Secretory proteins & waste)

Endocytosis

Into cytoplasm

HYPOtonic

Lower solute concentration

Concentration is greatest inside cell

Water floods in causing it to swell and possibly burst (Plasmolysis)

HYPERtonic

Higher solute concentration

Concentration is greatest outside cell

Water flows out and causes cell to shrink (CRENATION)

ISOtonic

Equal solute concentration

Water flows in and out freely (Dynamic Equilibrium)

Channel

Transport protein, Hydrophobic pathway, Allows IONS to diffuse

Voltage gated: open/closed in response to separation of charge (potential difference/voltage)

Channel doesn’t open unless gradient is large enough OR closes when gradient is too large

BEAN

Carrier

Transport protein, Protein binds specific solute and changes conformation, moving molecule along gradient

TOOTH

Symport

Driving ion with Secondary ion

Antiport

Driving ion against Secondary ion

Pinocytosis

Membrane indents to form vesicle containing water and dissolved solutes

Phagocytosis

Cell engulfs another cell by extending membrane around it (Pseudopods)

Receptor Mediated Endocytosis

Molecules bind to specific receptors on surface and then form vesicle

... cytosol to inside the nucleus of the cell

Proton pumps move hydrogen from...

NEGATIVELY CHARGED IONS

All primary active transport pumps move ______________ across membranes

the concentration gradient of an ion

Secondary active transport pumps use ____________________, established by the primary pump, as their energy source