Transport In Cells Flashcards
Define diffusion
The net (overall) movement of particles from an area of high concentration to and area of low concentration down a concentration gradient
- it is a passive process meaning no energy is needed
When does diffusion occur until?
Until equilibrium is reached
What SA:V ratio do small organisms have, and what does this mean ?
High SA:V ratio
Organisms with high SA:V ration can get all substances they need by diffusion
What SA:V ratio do large organisms have, and what does this mean ?
Low SA:V ratios
This means they can’t get all the substances they need via simple diffusion, so they need specialised exchange surfaces
How is the small intestine adapted to maximise rate of absorption of digested food products
- Large SA, villi and microvilli
- Thin 1cell thick walls (short diffusion distance)
- capillaries for blood flow to maintain a steep concentration gradient
How are the lungs adapted to maximise gas exchange?
Alveoli have high SA for diffusion
Capillaries for blood flow maintains a steep concentration gradient
Thin cell wall for short diffusion distance
What are features of a good exchange surface?
- Large SA
- Good blood supply
- Thin cell wall
What is a dilute solution?
A solution with a high proportion of water ( high water conc.)
What is a concentrated solution?
Where there is a low proportion of water ( low water conc.)
Define Osmosis
The net movement of water molecules from a dilute region to a concentrated region down a concentration gradient across a partially permeable membrane (PPM)
What is a hypOtonic solution?
Where there is a higher water concentration outside the cell than inside
Water will move in via Osmosis
What is a hypERtonic solution?
Where there is a higher concentration of water inside the cell than outside.
Water moves out of the cell via Osmosis
What is an Isotonic solution?
Where there is an equal concentration of water inside and outside of a cell
There is no NET movement
What happens to an animal cell in a hypertonic solution?
Water leaves cell via Osmosis across a PPM, leaving cell shrivelled
It is CRENATED
What happens to a plant cell in a hypertonic solution?
Water leaves cell via Osmosis across a PPM.
When some water is left, the cell is less rigid and has a smaller vacuole. It is FLACCID
When lots of water has left, it has a very small vacuole, and cell membrane + cytoplasm pull away from cell wall into star shape
Cell is PLASMOLYSED
