5.1 Diffusion Flashcards
Simple Diffusion
Movement down concentration gradient
With time (3 answers)
1) concentration gradient dissipated
2) molecules move spontaneously from area of high concentration to low
3) entropy increased
Membrane present (3 answers)
1) ions cannot cross lipid bilayer
2) ion concentration can be massively different on either side of membrane
3) if concentrations are different we get a gradient
If hole punched in membrane (3 answers)
1) ions flow down gradient until equal on both sides
2) equilibrium set up
3) molecules facilitate diffusion
What proteins are holes? (3 answers)
1) pumps
2) carriers
3) ion channels
Why are ions spread out? (3 answers)
1) molecules in liquid are in constant motion due to thermal agitation
2) for water molecules average center to center distance is about 2.8A
3) go for short distances (A) and not for long (pescs) before bumping into each other
How quickly do ions diffuse?
Adolf Fick
Number of molecules moving across an interface is proportional to: (2 answers)
1) the area of interface (A)
2) concentration gradient
Einstein
showed that diffusion was due to random walk of molecules
How far will a diffusing molecule be from its starting point after a given time?
Depends whether molecule moves in 1, 2, or 3D
1D
movement along DNA
2D
movement in membrane
3D
movement in liquid (cytosol, extracellular fluid)
Diffuse furthest is which dimension?
3D
Why do molecules travel furthest in 3D?
because they have a lower chance of bumping into each other
2D and catalysts
Provide surface for molecules to bump into each other
2D and signaling molecules
Signaling molecules in membranes have a higher chance of interacting
3D and signaling molecules
signaling molecules have longer ranges if not bound to membrane
