Topic 5- Membranes and Transport Flashcards
Describe the basic structure of a membrane
Made of a a phospholipid bilayer, two layers of lipids that create a barrier around the cell.
Saturated tails makes the membrane stable and thicker
Unsaturated tails make the membrane more fluid.
Cholesterol (only in animal cells) maintains the fluidity. AT room temperature it keep things stable, but when it gets cold it limits solidification.
What is the fluid mosaic model
The idea that the membrane is fluid, ie. the proteins, lipids, cholesterol end everything else are free to flow around.
How are cell membranes synthesized
The ribosomes in the rough ER make proteins that are put in vesicles, sent to the golgi apparatus to be modified, then fuses with the membrane.
The lipids are created in the smooth ER
Describe the idea of diffusion and osmosis.
Diffusion is the idea that molecules want to go from places with high concentration to places of low concentration. Osmosis is a type of diffusion that is water moving across a semi permeable barrier(only certain things can cross). Water will sometimes move to even out the concentration if the solute cant’ get across the barrier.
What makes plants rigid and shriveled?
Plants keep themselves in a hypotonic state with having more solute inside its membrane which pulls water inside keeping it rigid. When its is shriveled it is in a isotonic solution cause it will deflate. Plants have a cell wall which keeps the plant from exploding.
Describe Membrane selectivity
Non polar things can easily move through the membrane because it can interact with the hydrophobic region of the membrane.
Polar and charged things cannot pass through the polar region.
Describe Facilitated Diffusion
Protein in the membrane creates a path for molecules to pass through. The amino acid lining the path controls what molecules can get through. No energy because it is still just diffusion.
Aquaporins are channel proteins for water. can be responsible for them bursting
What is the difference between active and passive transport?
Passive transport has to go with the concentration gradient, thus requires no energy
Active transport can go against the concentration gradient thus does not require energy.
Describe a Proton Pump and why it is important
Protein that pumps protons from inside the cell outside. This makes the cell more negative on the inside. This difference in charge creates the electrochemical gradient. This can be used as a power source for the cell. The flow of the protons wanting to come back in creates power.
Ex. once protons are pumped out, in order for it to come back it needs to bring something else with it
Describe Cotransports.
A transport system for when 2 molecules move across the membrane at the same time.
How does osmosis apply to cell membranes?
Water will move across the semi permeable cell membrane to even out the concentration of solutes.
- Hypotonic Solutions- Water is flowing into the cell because the solution has a higher concentration of solute inside the membrane. can cause a cell to explode
-Hypertonic Solutions- Water flowing out because there is a higher concentration of solute outside the cell. will cause a cell to shrivel up.
-Isotonic Solutions- Net 0 flow of water because of an equal concentration of solute.
