The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

This discussion is now closed.

Check out other Related discussions

Help in Biology Plasmolysis (AS-OCR)

:confused: Hello to anybody who can help me! :smile:

I have to devise a plan for a practical about plasmolysis. All the info we're given are as follows;

Heavy metal ions such as those of lead are toxic to cells.

You are required to plan an investigatio to determine the lowest concentration of lead ions that causes cell membranes to lose their partial permeabilty.

In plant cells loss of membrane partial permeability results in cells failing to show plasmolysis and deplasmolysis (recovery from plasmolysis) when placed in appropriate solutions.

we'll be using
onion cells (epidermis)
and given sucrose buffer solutions
as well as 1M of lead nitrate solution

I know that I have to make 0.1M, 0.2M all through to 0.9 and 1M. solutions of lead nitrate. :redface: To test the lowest concentration.

I've had a chance to play around with the apparatus were given and I've found out that when I placed the onion peice in 1M solution of lead nitrate, nearly all of the cells (when looked under a microscope @ high power) are plasmoylsed. And when placed in 0.5M, the % plasmoysis was much lower meaning not all plasmolysed.

I don't know why though. :confused: Does it mean that I have to find out at which concentration did incipient plasmoysis occur? and this will be the lowest concentration.

I also figured out that Lead nitrate works exactly the same as sucrose solution. (we've done the experiment before) and the higher the molarity, the more plasmolysed the cells are. Because it goes down the gradient of the water potential.

But I really need help! I have no idea why the sucrose solution is there! in my vague plan, I didn't really need sucrose. Apparently it was for comparison, but I don't get why??!!

please help! thank you very much!! :p:
Reply 1
Avatar for DreamGirl_23
DreamGirl_23
OP
any help will be kindly appreciated! :frown: I'm really really stuck here!

thank you!!!!!! :biggrin:
Reply 2
Avatar for Dstbgre
Dstbgre
Hi
I have not done this pratical so all of this is based on the information which you have said. I think it is as follows:
Firstly you will need to use the sucrose solutions to work out at what concentration the cells will plasmolyse. Using this you can work out at what concentration the cells should deplasmolyse. Then you can use the lead nitrate and look at what concentrations the cells will plasmolyse and at which concentrations they wont. If the lead has no effect then this should be identical to the sucrose. If the cells do not plasmolyse with the lead but do with the sucrose then the cell has been poisoned. However from what you have said you may need to use a stronger lead nitrate solution because the cells do not seem to be poisoned even at 1M.
I hope this helps.

Related discussions

Latest

Trending

Trending

Articles for you