Flashcards in 4.2- DIFFUSION Deck (29)
What is exchange of substances between cells and environment that require metabolic energy called?
What is exchange of substances between cells and environment that don't require metabolic energy called?
What is diffusion an example of?
Do all movement involve energy?
What does 'passive' mean in passive transport?
energy comes from natural, inbuilt motion of particles, rather than from some external source i.e. ATP
How are all particles constantly in motion?
due to K.E. they possess
What is the motion of the particles?
random with no set pattern to the way particles move around
Where are particles bouncing off of constantly?
bouncing off one another as well as off other objects i.e. sides of vessel in which they're contained
What is the definition of diffusion?
net movement of molecules/ions from region where they're more highly concentrated to one where their concentration is lower until evenly distributed
Examples of molecules that can diffuse across the cell-surface membrane?
carbon dioxide and oxygen
Why do charged ions and polar molecules not diffuse across plasma membranes?
because of phospholipids in membrane
How is the movement of charged ions and polar molecules made easier (facilitated)?
by transmembrane channels and carriers that span the membrane
What is the process by which movement of charged ions and polar molecules made easier called?
Is facilitated diffusion an active or passive process?
What does facilitated diffusion rely on?
inbuilt motion (KE) of diffusing molecules
no external input of ATP from respiration
Does facilitated diffusion occur down or against a concentration gradient?
down a concentration gradient
How does facilitated diffusion differ from diffusion?
occurs at specific points on plasms membrane where there are special protein molecules
What two types of proteins are involved in facilitated diffusion?
protein channels and carrier proteins
What do protein channels form?
water-filled hydrophilic channels across the membrane
What do protein channels allow?
specific water-soluble ions to pass through
Are the channel proteins selective or not?
What does it mean for the channel protein to be selective?
each opening in presence of specific ion
if particular ion not present, channel remains closed
Why is channel proteins being selective a good thing?
control over entry/exit of ions
What do the ions do with the channel protein?
they bind with the channel protein
What happens when the ions bind to the channel protein?
causes channel protein to change shape in a way that closes it to one side of membrane + opens it to other side
What does an alternative form of facilitated diffusion involve?
carrier proteins that span the plasma membrane
What happens when a molecule i.e. glucose that's specific to the carrier protein is present?
it binds with the protein
What happens when the molecule binds with the carrier protein?
causes it to change shape in such way that molecule released to inside of membrane