8 MOVEMENT ACROSS MEMBRANES Flashcards
Define diffusion
The random movement of particles from an area of high concentration to an area of low concentration
How does an increased temperature affect diffusion
Molecules have more kinetic energy so move faster - diffusion occurs faster
How does increasing concentration gradient affect diffusion
Large concentration gradient will make particles move from high to low quicker
How does increasing the surface area and surface area : volume ration affect diffusion
- Larger SA increases diffusion as particles can move over a larger area
- Small structures have large SA:V ratios, so diffusion occurs quicker
Define osmosis
The net diffusion of free water molecules from an area of high water potential, to an area of low water potential across a partially permeable membrane
As more solute is added to a solution, what happens to the water potential
Falls
What is an isotonic solution
The solution outside the cell has the same water potential as inside the cell (no net movemement)
What is a hypotonic solution
The solution outside the cell has a higher water potential than inside the cell (net movement of free water molecules into cell)
What is a hypertonic solution
The solution outside the cell has a lower water potential than inside the cell (net movement of free water molecules out of the cell)
Why do plants wilt
There is not enough water to fill cells and so cytosplasm shrinks from cell wall
Define active transport
The movement of molecules from
Define active transport
The movement of molecules from an area of low concentration to an area of high concentration using ATP
What transport system moves molecules against the concentration gradient
Active transport
What transport system moves molecules against the concentration gradient
Active transport
How does active transport get molecules against the concentration gradient
Special carrier proteins in the cell membrane move them
