04.3H BIO Passive Transport WO/Toniciy (PART H)

Concentration gradient

A difference in concentration of a substance across a region

Against the concentration gradient

Movement of materials from low to high concentration; requires energy

Down the concentration gradient

Movement of materials from high to low concentration; no energy required

Passive transport

Movement of materials from an area of high concentration to low concentration; does not require energy; includes diffusion, osmosis and facilitated diffusion

Types of Passive Transport

Simple Diffusion

Osmosis

Facilitated Diffusion

Simple Diffusion (Definition)

Movement of materials from high concentration to low concentration HIGH → LOW; NO energy required; the membrane acts as filter and influences rate/timing but does NOT influence direction HIGH → LOW

Simple Diffusion (Types of Molecules)

Small nonpolar molecules like O2 and CO2

Lipid soluble molecules

Vitamins A, D, E, & K

Ethyl alcohol

Factors Affecting the Rate of Diffusion

Temperature

Size of the molecules

Osmosis

The net movement of water molecules from an area of high concentration to an area of low concentration across a selectively permeable membrane

Aquaporin

A transport channel protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane

Solute

A substance that is dissolved in a solution

Solvent

A liquid substance capable of dissolving other substances

Equilibrium

Dynamic condition in which the net movement of water into the cell is equal to the water leaving the cell

Lysis

Condition that results in animal cells that are placed in a hypotonic solution in response to water entering the cell and causing it to burst and die

Plasmolysis

Condition that results in plant cells that are placed in a hypertonic solution in response to water leaving the cell causing the contraction or shrinking of the cell membrane

Facilitated Diffusion (Definition)

The movement of materials from a high concentration to low concentration HIGH → LOW; carrier proteins required; NO energy required

Facilitated Diffusion (Types of Molecules)

Polar, hydrophilic molecules such as:

- Na+, K+, Ca+2 ions

- Some Amino acids

- Monosaccharides (ie. Glucose)