Transport Mechanisms Across Cell Membranes

Passive transport

Moves substances down concentration gradients using kinetic energy.

Active transport

Moves substances against gradients using energy.

Mediated transport

Requires transport proteins to move substances.

Non-mediated transport

Substances cross membranes without transport proteins.

Vesicular transport

Moves materials in vesicles via exocytosis or endocytosis.

Diffusion

Movement of molecules from high to low concentration.

Ion channels

Proteins allowing rapid ion passage without binding.

Gating

Control of channel pore opening by stimuli.

Facilitated diffusion

Passive transport via specific transport proteins.

Carrier mediated transport

Transport proteins undergo conformational changes during transport.

Saturation

Transport maximum when all binding sites are occupied.

GLUT

Transport protein facilitating glucose entry into cells.

Primary active transport

Directly uses ATP hydrolysis for transport.

Na/K ATPase

Pumps 3 Na+ out and 2 K+ into cells.

Electrogenic pump

Generates net current due to ion movement.

Secondary active transport

Uses ion gradients to move substances against gradients.

Pump-leak hypothesis

Continuous operation of Na/K pump due to ion leakage.

Concentration gradient

Difference in ion concentration across a membrane.

Hydrolysis of ATP

Energy release from ATP breakdown for transport.

Transport specificity

Transport proteins selectively bind specific substrates.

Transport inhibition

Reduced transport efficiency due to competitive binding.

Electrical excitability

Ability of cells to respond to stimuli via ion movement.

Intracellular pH maintenance

Regulation of pH through ion transport mechanisms.