Q1 Membrane Transport and the Regulation of Cell Volume

Bulk Flow

Requires a pressure gradient that moves fluids and gases from regions of higher pressure to regions of lower pressure

Diffusion

The passive movement of molecules from an area of higher concentration to an area of lower concentration (in terms of molecules)

Unidirectional Diffusional Flows

An increase in membrane area, permeability, and solute concentration will improve flow

Calculating Speed of Diffusion

x² = 2Dt ,, x = distance ,, D = diffusion constant ,, t = time

Molecule Size Determines Speed of Diffusion

Smaller molecules (with larger diffusion constants) diffuse faster than larger molecules (with smaller diffusion constants)

Simple Diffusion

Movement of molecules from a high to a low concentration (will not reach a maximum saturation)

Facilitated Diffusion

Passive movement of molecules across the cell membrane through the use of protein channels (will reach a maximum saturation)

Primary Active Transport

Moves solutes from an area of high concentration to an area of low concentration using ATP and protein channels

Secondary Active Transport

Moves solutes from an area of high concentration to an area of low concentration using protein channels and another solute moving down its concentration gradient

Osmosis

The movement of water across a membrane in response to a solute concentration gradient