Chapter 6: Lipids ii) Movement Across Membranes Flashcards
Only few kinds of molecules can cross the phospholipid bilayer. What are they?
Small, non-polar molecles (O2, CO2)
Some small, polar molecules (H20)
Some bigger lipids
Why can’t large polar molecules or ions pass through?
Because the surrounding water creates an attraction for larger molecules and ions.
How do most large polar molecules or ions cross?
By using proteins to let them thru
What are the two types of transport across membranes?
Passive transport (no E required) Active transport (E required)
What are the 3 types of passive transport?
Diffusion, Osmosis, Facilitated diffusion
What is diffusion?
The tendency for molecules to go from [High] to [Low] i.e. Concentration gradient
What is osmosis?
The diffusion of water through a selectively permeable membrane.
If a solute cannot cross a membrane the net movement of water is?
From an area of low [solute] to high [solute].
What matters is the # of solute particles and how many H20 molecules can H-bond to it.
What is osmotic pressure?
Pressure with which water crosses a selectively permeable membrane, from pure water to an aqueous solution.
What does it mean to be isotonic?
When 2 solutions have the same [solutes]
What does it mean to be hypertonic?
When the {solutes} is higher
What does it mean to be hypotonic?
When the [solutes] is lower
What is osmoregulation?
The ability for an organism to regulate its water and solute balance
What is facilitated diffusion?
Diffusion through a membrane protein by molecules that can’t go through phospholipids
What is active transport?
Movement against a concentration gradient
