Biology Coursework Effect of Different Concentrations of Sucrose on Potato Tissues.

Hina Raja

11TJ

Biology Coursework Effect of Different Concentrations of Sucrose on Potato Tissues

AIM

Aim of this experiment is to investigate and understand how diffusion process allows movement of molecules from one concentration of solution to a different concentration of solution. I will conduct an experiment by immersing a sliced potato in different concentration of sucrose solution and measure mass of the potato at intervals to see if diffusion has taken place.

Potato is chosen because its cells contain starch (carbohydrates) within it. (This proof was obtained using iodine solution. The solution turned blue/ black in colour because there was starch present). Since sugar molecules are large the theory says it will take longer for the molecules to diffuse. This will allow us to see the diffusion take place both ways, into the cell and out of the cell.

The results from this experiment will allow me to understand how chemical exchange takes place within living cells. This will provide me with the understanding of respiration process with in a cell takes place (Transfer of food and oxygen into cell and by-products like carbon dioxide and water out of the cell), how hormones such as insulin works within or body and how many other chemical processes take place in our body.

BACKGROUND INFROMATION

The theory of diffusion defines that molecules move from high concentration to a low concentration. In case of osmosis the definition is the movement of higher concentration of water to a lower concentration of water. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium. This means that the molecules are equally distributed throughout an object with its surroundings, with no area having a higher or lower concentration than any other.

Plant cells can become turgid. Potato cells have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. 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. Turgidity is very important to plants because this is what makes the green parts of the plant stand up into the sunlight.

When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become flaccid. This is the opposite of turgid. The content of the potato cells shrink and pulls away from the cell wall. These cells are said to be plasmolysed. Therefore the mass of the potato chip decreases.

When plant cells are placed in a solution that has exactly the same osmosis strength as the cells they are in a state between turgidity and flaccidity, incipient plasmolysis. This is also called isotonic. Therefore the potato chip’s mass stays the same.

PRIDECTION

I predict that the concentrations of water and sucrose solution will eventually balance out inside and outside the potato cell. Because potato cells itself has high concentration of sucrose in it, any lower concentration of solution used in the experiment would mean the potato will loose weight eventually since sugar molecules density is more than water.

REASONS FOR PREDICTION

Whilst the transition of sugar molecules one way and water molecules the other way is taking place, the mass of the potato is expected to increase and then decrease in case of the higher concentration solution and vice ...