Diffusion Flashcards
Definition of diffusion?
Net movement of molecules from an area of high concentration to an area of low concentration through a phospholipid bilayer
Requirements for diffusion?
All particles are in constant motion
Motion is random
Particles are constantly bouncing off eachother
Why do molecules like oxygen and carbon dioxide pass directly through the membranes unassisted?
They are non-polar, small and not-charged
Why do charged ions and polar molecules not diffuse easily?
Because they have hydrophobic fatty acid tails
Ficks law?
SA (big) x concentration gradient (big) / diffusion distance (small)
Is facilitated diffusion active or passive?
Passive (high to low concentration) across transmembrane channels (channel/carrier proteins) that span the membrane
Does facilitated diffusion require ATP?
No
Do channel proteins change shape?
No
Do carrier proteins change shape?
Yes
What type of core do channel proteins have?
A water filled core
What type of molecules do channel proteins transport through?
Ions- charged
Carrier proteins?
Change shape
Take larger things e.g. glucose
Uncharged
How does water pass through?
By simple diffusion
But not as soluble in lipids
Most enters via channel proteins (hydrophilic pores)
Factors increasing rate of simple diffusion?
Concentration gradient
Thickness of membrane
Factors increasing rate of facilitated diffusion?
Concentration gradient
Number of channel/carrier proteins
Order of active transport?
1) the molecule binds to receptor on channel of a carrier protein
2) ATP binds to the protein and splits into ADP + 1 phosphate molecule
3) the carrier protein changes shape to transport the molecule from one side of the membrane to the other
4) the phosphate molecule is released from the protein and the protein reverts to its originals shape
5) ADP reforms ATP (respiration)
