63 WJEC Biology AS Level - Marianne Izen - 2nd Edition (1.3 Cell Membranes And Transport) Flashcards
When is a cell said to be turgid?
When the cell can take in no more water, it is turgid.
Why is turgor important?
Turgor is important to plants, especially young seedlings.
It provides
a. support
b. maintains their shape
c. holds them upright.
Draw a diagram to explain turgid, incipient plasmolysis and plasmolysis along with potentials.
What is the relationship between pressure potential, water potential and solute potential in animal cells.
An animal cell has no cell wall and so pressure potential does not have to be considered.
The water potential is therefore the same as the solute potential
What happens when red cells are placed in:
- distilled water
- concentrated salt solution
If red blood cells are in distilled water, water enters by osmosis and, without a cell wall, they burst. This is haemolysis.
If red blood cells are placed in concentrated salt solution, water leaves the cells and they shrink, becoming ‘crenated’.
100 kPa.
1 = B
2 = B, D
3 = B, C
4 = A, D
What do some species of fish have to cope with?
Some species of fish, including eel and salmon, migrate between the sea and fresh water.
Hence they have to cope with the changing water potential of their environment and its effects on their physiology.
How do some species of fish cope in sea water?
Sea water has a high salt concentration.
Hence in a marine environment, fish tend to lose water by osmosis.
Na+ and Cl- ions diffuse across their gills, down their concentration gradient.
On moving from fresh to salt water, to compensate, fish must
a. drink a lot of water
b. make only a small volume of concentrated urine
c. secrete Na+ and Cl- ions at their gills.
How do some species of water cope in fresh water?
Fresh water has a very low salt concentration.
In fresh water, fish tend to take in water.
Na+ and Cl- ions diffuse out across their gills.
On moving from salt to fresh water, fish must
a. lose water
b. produce a large volume of dilute urine
c. absorb Na+ and Cl- ions at their gills.
