Membranes Flashcards
Why is it important for membranes to be very fluid?
Membranes are very fluid in order to allow proteins inserted into membrane to interact with each other
What type of protein can integrate into the membrane? Why?
-One or multiple alpha-helices are able to integrate into protein (they are amphipathic)
This is due to the non-polar amino acids being hydrophobic, and the hydrogen bonds/polar amino acids are hyrdophilic
In which directions are membrane proteins able to move?
What is the consequence of this regarding proteins in the membrane?
Laterally ONLY (not vertically) This means the side of the protein sticking out sides of membrane never changes
Describe process and function of freeze fracturing
Freeze fracturing is a process to break about a frozen cell.
-This works because freezing tightly binds the phospholipids to water surrounding it by Hbonding. Meanwhile the lipids are held together by Vander waals.
This allows us to split a membrane in half and view the inside
What is main function of membranes?
Main function of membranes is the serve as a barrier and to selectively transport molecules the cell needs or needs to get rid of
Are ions able to cross a membranes?
NO
What is the process of diffusion?
Diffusion consists of the passive mixing of substances along the concentration gradient until it reaches equilibrium in the solution (no more net movement dG=0)
What 3 main thing affect rate of diffusion?
- Steepness of concentration gradient
- Size of molecule
- Temperature (high temp speeds up diffusion)
What is osmosis?
Refers to the diffusion of water across a selectively permeable membrane.
Water moves from regions of low solute concentration to regions of high solute concentration
3 types of osmotic solutions
- Hypertonic: higher solute concentration outside of membrane
- Hypotonic: higher solute concentration inside of membrane
- Isotonic: Same solute concentration outside and inside membrane. No net water flow!
What are the two types of cell membrane transport?
- Active transport (against concentration gradient- requires energy)
- Passive transport
What are two types of passive transport
- Channel Proteins (channel in membrane that opens- ions can flow along their electrochemical gradient)
- Carrier Proteins (bind to a substance then let it through other side) ex: glucose carrier protein.
Explain primary active transport
LOW TO HIGH CONCENTRATION GRADIENT
-Requires ATP
Sodium Potassium pump:
1) 3Na+ ions bind to protein, phosphate binds to protein and breaks off ATP
2) Phosphate causes shape change in protein and releases Na+ ions to outside of cell
3) 2K+ ions bind to protein, release phosphate
4) Phosphate release causes shape change (back to original) and releases K+ into cell
What is the point of the Sodium Potassium Pump?
The sodium potassium pump sets up a concentration gradient that allows other transport processes to occur
Describe Secondary Active Transport with an example
Uses gradient established by sodium potassium pump. It uses established gradient to move other substances.
Example: Sugar sodium co-transporter: In the gut, it is important to maximize sugar uptake. A cotransporter is able to transport a sugar across a membrane ONLY when paired with Na+. This is when the gradient established by the Sodium potassium pump is put to use.
