Miss Cane's Coursework Test Flashcards
Describe the function of the cell wall of plant cells.
The cell wall is a rigid structure that surrounds plant cells (they are on the outside of the plant cell plasma ((cell surface)) membranes). Beacuse it is held rigid by the pressure of the fluid inside the cell (turgor pressure), it supports the cell and so helps to support the whole plant.
What would happen to the shape of the plant cells treated with such an enzyme?
The shape of the plant cells would change as the enzymes would break down the matrix of pectin which supports the cell wall as a rigid structure.
Why is it important that the sucrose solution is isotonic to the plant cells?
It is important as it would mean that the shape of the plant cells would not change. This is because there would be no overall movement of water due to the isotonic solution having an equal water potential to that inside the plant cells.
In the space below draw an outline diagram of the cell and the distribution of the chloroplasts only.
Why was it necessary to heat the plant material and sucrose solution in a water bath before adding the enzyme?
As enzyme action is temperature dependant the heating was neccessary because it ensure that the solution was at an optimum temperature for the reaction to be carried out.
Explain what would happen if the plant cells were placed in…
a) Sucrose solution of equal concentration to that inside the cells?
As there would be an equal concentration of sucrose solution to that inside the cells it would act as an isotonic solution - it would have a water potential equal to the plant cells as it would have the same amount of solutes and ‘free’ water molecules to that inside the cells. This means that there would be no net movement of water molecules but instead, the water molecules would pass into and out of the cell in equal amounts, thus the cell’s shape would remain the same.
Explain what would happen if the plant cells were placed in…
b) Sucrose solution of greater concentration than that inside the cells?
As there would be a greater concentration of sucrose solution than that inside the cells it would act as a hypertonic solution - it would have a lower water potential (kPA) as it would contain more solutes and less ‘free’ water molecules than that inside the plant cells. This means that the net movement of water would be from the inside to the outside of the cells. So, the water molecules would diffuse across the plasma membranes of the cells down a water potential gradient from the inside to the outside of the cells by Osmosis. This would cause the cells to become flaccid (limp). In the plant cells, the vacuole and cytoplasm would shrink as they would lost water and the cell surface membrane would pull against the cell wall leading to plasmolysis in the plant cells.
Explain what would happen if the plant cells were placed in…
c) Sucrose solution of lower concentration than that inside the cells?
As there would be a lower concentration of sucrose solution than that inside the cells it would act as a hypotonic solution - it would have a higher water potential (kPA) as it would contain less solutes and more ‘free’ water molecules than that inside the plant cells. This means that the net movement of water would be from the outside to the inside of the cells. So, the water molecules would diffuse across the plasma membranes of the cells down a water potential gradient from the outside to the inside of the cells by Osmosis. This would cause the cells to become turgid (swollen). In the plant cells, the swelling cytoplasm and vacuole would push the membrane agasint the cell wall. The cell would not burst, because the wall would eventually stop the cell from getting any larger. Osmosis would stop at this point, even though there may still be a water potential gradient.
