Biology practical investigation

Practical investigation.



Introduction



Heavy metals like mercury and lead are toxic. They are non--competitive enzyme inhibitors, neurotoxins and reduce the partial permeability of cell membranes. Deposits of heavy metals accumulate in the body causing serious damage. People may ingest heavy metals – particularly lead ions – in various ways, chiefly; fumes from leaded petrol, lead based paints and drinking water from lead pipes (Biological Science).
Living cells have cell membranes, which regulate substances entering and leaving the cell. They are therefore semi-permeable. The membrane is made up of proteins like cholesterol and phospholipids. These form a phospholipids layer in which the hydrophobic tails point inwards and the hydrophilic heads point outwards. This is due to the way the react with water.

When the protoplast of a cell is in an area of high water potential, water enters through the semi-permeable membrane into the cytoplasm expanding it. This pro...