Transport Across Membranes Flashcards
What is diffusion
Diffusion is the net movement of molecules from on area of high concentration to an area of low concentration down a concentration gradient and its a passive process
What molecules can pass through simple diffusion
Lipid based molecules
Carbon dioxide
Oxygen
Small molecules
What is facilitated diffusion
Using carrier proteins to diffuse large molecules
Use channel proteins to transport charged or polar molecules. They have specific proteins for specific molecules
What is active transport
The net movement of molecules and ions through a cell membrane from a region of low concentration to a region of high concentration against the concentration gradient using ATP.
What is exocytosis
It is the process by which materials are transported out the cell
Explain the process of exocytosis
The substances that want to be released are packed into a vesicle which travels to the cell surface membrane where they fuse together , secreting the substances pout
Explain the process of endocytosis
The cell surface membrane engulfs the material forming a small sac around it and transporting it in the cell
What are the 4 factors that affect diffusion
1)Temperature
2)Concentration
3)Surface area
4)Distance
What is osmosis
The movement of water across a partially permeable membrane from a region of high water potential to a region of low water potential. It’s a passive process
Explain the term water potential
water molecules are free to move around they have a high water potential. If a solute is added , it is attracted to the water so it can no longer move around freely so it has a lower water potential
What is a hypertonic solution and how does this affect plant and animal cells
When the external solution has a lower water potential then the solution in the cell so water moves out the cell . Th cell loses volume and shrinks
Animal- shrivels up , the plasma membrane crenates
Plant -protoplast moves away from /the cell wall and the cell becomes plasmolysed
What is an isotonic solution
When the water potential of the external and internal solutions are the same so there is no net movement of water - cell shape isn’t altered
What is a hypotonic solution and what affect does this have on animal and plant cells
It is when the water potential of the external solution is higher than the solution in the cell so water moves in by osmosis
Animal- cell swells and bursts (cytolysis)
Plant-protoplasm swells , increased turgo pressure on cellulose cell wall, cell becomes turgid
