Membrane Dynamics Flashcards
What are the mechanisms by which molecules move across membranes?
- Simple diffusion
- Simple diffusion through a channel
- Facilitated diffusion
- Active transport
What is simple diffusion?
Movement from higher to lower concentrations
What is simple diffusion through a channel?
Movement from higher to lower concentrations through the pore of a membrane channel protein
What is facilitated diffusion?
Movement from higher to lower concentrations via a membrane carrier protein
What is active transport?
Movement from low to high concentrations
What are channel proteins?
Provides space which a specific substance can pass through while diffusing
ex. for water, the channel protein is polar on the inside and non polar on the outside so that water can pass through the membrane
What are carrier proteins?
The protein changes shape to spit out what it’s transporting
First it binds to the substance, then the protein changes shape allowing the molecule to pass through
What is membrane potential?
The voltage of a membrane (-50 to -200mV)
What is chemical force?
The ion’s concentration gradient
Higher concentration on one side of the membrane is a store of energy due to entropy
What is electrical force?
Difference in charge across the membrane
What is the electrochemical gradient?
The combination of the store of energy due to chemical force, and the difference in membrane potential
What is co-transport?
Allows two substances to move across the cell.
What are proton pumps
Moves H+ across the membrane against its concentration gradient
What is tonicity?
The ability of the surrounding solution to cause a gain or loss of water within the cell
isotonic, hypotinic, hypertonic
What does it mean when a solution is isotonic?
Iso=same; no net movement of free water across the plasma membrane
