Describe how turgor pressure builds up and identify 2 forces defining each of them
Turgor pressure is the pressure exerted by the fluid inside the cell against the cell walls which helps to maintain the shape, rigidity and mechanical strength of the cell. The process of building up turgor pressure involves two main forces which are as follows:
1. Osmotic Pressure: It is the force created by the movement of water molecules from an area of higher water concentration to an area of lower water concentration across a semi-permeable membrane. In plant cells, the solutes such as ions, sugars and amino acids are higher in concentration inside the cell than outside, causing the water to move inside the cell by osmosis. This results in the swelling of the cell and increases the turgor pressure. This force is controlled by the concentration gradient of the solute and the selective permeability of the cell membrane.
2. Elasticity of the Cell Wall: The cell wall of plant cells is made up of cellulose, hemicellulose, and lignin. These molecules work together to provide the cell wall with structural support and elasticity. As the cell takes up water through osmosis, the cell wall resists stretching and expands limitedly creating tension within. This force can also help in building turgor pressure as the cell wall is subjected to a combination of chemical and physical forces. This force is controlled by the rigidity and elasticity of the cell wall.
Overall, turgor pressure is achieved by the combination of these two forces. It is essential for plant cells as it allows them to maintain their shape, support their structures, and regulate water movement.