Membrane Flashcards
What is cell membrane composed of?
Phospholipid bilayer
What types of molecules can diffuse readily through cell membrane?
lipid soluble molecules and gases
(water-soluble molecules and organic anions - proteins - need help)
What molecules are involved in simple diffusion?
small, lipid soluble molecules and gases
Where do molecules pass through in simple diffusion?
Pores or phospholipid bilayer
What is the concentration gradient of simple diffusion?
Moves down the concentration gradient from high to low concentration
Greater concentration gradient = greater rate of diffusion
Brownian motion
random movement of particles suspended in a fluid resulting from their collision with fast moving atoms in gas or liquid - plays a role in simple diffusion
Simple Diffusion?
Passive - no ATP
small, lipid soluble molecules and gases
Down the concentration gradient
Facilitated Diffusion
Molecules diffuse across the membrane with the assistance of carrier protein
Goes down concentration gradient - passive
What does carrier protein do in Facilitated Diffusion?
Aids in movement of polar molecules across membrane (sugars, AA, etc)
Active Transport
Moves against concentration (low to high)
Moves select molecules against the concentration gradient
Substance binds to protein carrier that changes conformation to move substance across membrane
Needs ATP
Ex. Na+/K+ pump
Secondary Active Transport
Substance is carried up its concentration gradient without ATP catabolism
Powered by the chemical energy in the substance diffusing down its concentration gradient - this energy is used to push another substance against its gradient
Secondary Active Transport energy comes from?
The kinetic energy of movement of one substance down its concentration gradient powers the simultaneous transport of another up its concentration gradient (molecule moving down concentration gradient fuels the molecule moving up concentration gradient)
NO ATP
What is a channel?
Membrane spanning protein that forms a ‘pore’ through the membrane
What do pore loops do in channels?
They dangle inside the channel and creates a selective filter
What are Gated Channels?
Is a channel that is closed off by a protein acting as a gate
When the gate is closed no diffusion takes place
Under certain conditions the gate is open for diffusion
