Diffusion Flashcards
Diffusion definition
Net movement of molecules from a region of higher concentration to a region of lower concentration
What happens in diffusion
Move down a concentration gradient until equilibrium
Movement through phospholipid bilayer
What can’t diffuse by simple diffusion
Ions, large molecules and polar molecules
How do molecules diffuse if not by simple diffusion
Facilitated diffusion
What are the two types of facilitated diffusion
Channel and carrier proteins
How do they diffuse by channel proteins
Leak channels are always open and specific to one molecule eg sodium ion channel
Gated are opened by stimulus (chemical or electrical) and is specific to bind to particular molecules
How do they diffuse by carrier proteins
The carrier proteins binds to a molecule as it is a specific shape and changes shape to allow the molecule to pass through
What is water potential
Measure of the tendency of water molecules to diffuse from one place to another e.g pure water has highest water potential
What is water potential measured in
KPa
value of water and solutes in water potential
Water is 0kPa
anything with less water potential is negative
Osmosis definition
Net movement of water down a water potential gradient across a partially permeable membrane
Why is water potential lower in cells than pure water
It contains salts sugars and substances dissolved in cytoplasm and vacuole contains dissolved substances in plant cells
