Movement of Substances Flashcards
What is the definition of diffusion?
The net movement of particles from a higher concentration to a lower concentration down a concentration gradient until equilibrium
What is the definition of osmosis?
Net movement of water molecules from a higher water potential to a lower water potential through a partially permeable membrane
How does the concentration gradient affect the rate of diffusion?
the steeper the concentration gradient, the faster the rate of diffusion
How does the diffusion distance affect the rate of diffusion?
the shorter the diffusion distance, the faster rate of diffusion. exchange of substances in living organisms occurs at areas that are one cell thick (e.g. lungs)
How does the surface area to volume ratio affect the rate of diffusion?
the higher the surface area to volume ratio, the faster the rate of diffusion. specialised cells for absorbing nutrients have high surface area to volume ratios (e.g. root hair cells)
What is solute concentration?
Solute concentration is the number of solute molecules per unit volume
What is water potential?
the ratio of water molecules to solute molecules in a solution
How does osmosis affect living organisms?
Cells are surrounded by living, partially permeable membrane. Cell walls of plants are fully permeable, and allows most dissolved substances to pass through
Why would a potato strip become longer?
- solute concentration in the solution lower than cell sap
- water potential in the solution higher than water potential in cell sap
- movement of water molecules from the solution into the cell sap via osmosis
What will happen to a potato cell after placing it in a solution with higher water potential
Potato cell will become turgid, cell increase in size, larger vacuole, cytoplasm will be pushed against the cell wall, rigid cell walls prevent the cell from bursting
What would happen to a potato strip if it is placed in a solution with lower potential?
the cell will become flaccid/plasmolyzed, cell will decrease in size, vacuole will decrease in size, cell membrane will shrink and pull away from the cell wall
Why would a potato strip become shorter in length?
- solute concentration in the solution higher than the cell sap
- water potential in the solution lower than water potential in the cell sap
- movement of water molecules from the cell sap into the solution via osmosis
What would happen to a red blood cell if it is placed in a solution of higher water potential?
Due to RBC not having a cell wall to prevent bursting, it will increase in size/ expand and burst (lyse)
What would happen to a red blood cell if it is placed in a solution of lower water potential?
RBC will shrink, spikes will appear on the cell membrane and therefore becomes crenated
What is the similarity between diffusion and osmosis?
- particles move down a gradient
- passive processes (no energy required)
