CH 6: D. passive transport

Passive Transport

movement of molecules across a selectively permeable membrane without using energy

Diffusion

type of passive transport that involves moving molecules (solutes) from an area where its highly concentrated to where there’s a low concentration

in other words moving along its concentration gradient

2 types:

Facilitated diffusion

Simple diffusion

Osmosis

passive transport via movement of the solvent (ex water)

How does Diffusion happen?

it happens because molecules (solute) in a solvent have a tendency to spread out evenly

leading to the movement of a high concentration to low (spread)

while molecules diffuse randomly when put inthey have a net movement

Net movement

when during diffusion the molecules move mainly in one direction (in order to even out the space)

ex. dumping solute on left half so molecules diffuse to the right

Equillibrium

the state when (all) solute molecules are spread evenly throughout the solute

What kinds of molecules can pass membrane more easily?

small hydrophobic (non-polar) molecules

ex.

oxygen - yes - not charged, small

CO2 - yes - non charged (double bond cancels out)

Methane - yes - (CH4) non polar

What kinds of molecules struggle to pass membrane?

large hydrophilic (polar) molecules

ex.

salt - no: polar

water - no: small but polar

sucrose - no: large, some polar

Simple diffusion

molecules passing through the membrane without help of transport molecules (small and hydrophobic)

Facilitated diffusion

molecules which enter the membrane by transport molecules or with they’re help (speeding up passing) or allowing since they’re too large or hydrophilic to pass

Transport proteins

transmembrane proteins (pierced) which help the movement of molecules past the membrane

ex.

Carrier Proteins (transport)

protein that gives a binding site for molecule, binds to it, configures itself so molecule faces into the cell, then protein steps into the cell to release molecule

ex. glucose

Channel Proteins (transport)

protein serves as a hydrophilic passageway for certain hydrophilic substances