Investigating the Effects of Sucrose Concentration on Osmosis in Potato Tissue

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Investigating the Effects of Sucrose Concentration on Osmosis in Potato Tissue

PLANNING

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We have been asked to research the effects of sucrose concentration on

osmosis in potato tissue. Osmosis is the spontaneous movement of a

solvent (-in this case water) from a place where its chemical

potential is higher to another place where it is lower, through a

semi-permeable membrane (-such as a cell membrane). A cell membrane

lets smaller molecules such as water through but does not allow bigger

molecules to pass through. The smaller molecules will continue to

diffuse across the membrane until the area in which the molecules are

found reaches a state of equilibrium, meaning that the molecules are

in a steady state, with molecules moving in and out of the membrane,

however with no net loss or gain.

Plant cells always have a rigid cell wall and cell membrane

surrounding them. When they take up water by osmosis the cells start

to swell up, but the cell wall prevents them from bursting, (-which is

what animal cells, who have no cell walls would do), the plant cell is

then said to be turgid. When turgid, the pressure inside the cell

rises and eventually the internal pressure of the cell is so high that

no more water can enter the cell. This hydrostatic pressure works

against osmosis, even when the plant cell's water potential is greater

than that of the outsides. Turgidity is very important to plants

because this is what makes the plant "stand up" and acts as a form of

support.

The opposite of turgidity is plasmolysis, this is the retraction of

the cytoplasm from the wall of a vacuolated plant cell as a result of

osm...

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...ETY

I will have to wear goggles to prevent the sucrose liquid getting into

my eyes, take care with the sharp scalpel, and to wear aprons to

prevent splashes getting on my uniform.

Preliminary work-shapes my understanding

The preliminary work let me decided on some crucial factors:

-Time for experiment: 10 minutes

-Amount of solution: 5ml

-Length of potato: 3cm-make sure no skin is on the potato, as it will

block the osmosis happening on that part of the potato, therefore

smaller surface area.

-Dry potato after experiment to get rid of excess water-see reasons

for this actions above

- Mixing beaker will be washed using water and dried using paper

towels-see reasons for this actions above

-Concentrations of sucrose to be used:

-0%

-20%

-40%

-60%

-80%

-100%

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