Question

How plasma membrane brings exchange of materials between cells and the surrounding medium as well as between membrane bound cell organelles and cytoplasm

Answer 1

Hint: Plasma membrane is also called a cell membrane. It usually helps in separating the Cell material from the outside environment. In bacteria and plant cells, plasma membrane is found in addition to the cell wall which is absent in animals.

complete answer:
Plasma membrane is the outermost covering of the cell that separates the content of the cell from the external environment. The plasma membrane allows the entry and exit of material in the cell. It is a selectively permeable membrane because it only selects material from passing it, therefore it is called a selectively permeable membrane.
Substances like Oxygen and Carbon dioxide move across through the process of diffusion. Diffusion is the process of movement of material from higher concentration to a lower concentration. Movement of substances like water molecules, protein is done with the help of osmosis. Osmosis is the process of movement of material from higher concentration to lower concentration through a semipermeable membrane.
If the medium of the cell has a higher water concentration than the surrounding then the water will move from higher concentration to the lower concentration that is from the cell towards the outer environment. Such a solution is known as a hypotonic solution.
Similarly, if the concentration of the cell is lower than the surrounding the water moves inside. Such a solution is called a hypertonic solution.
If the concentration is equal, water neither moves in nor out. Such a solution is called an isotonic solution.

 Note:
The structure of the plasma membrane can be described by a fluid mosaic model which includes phospholipid cholesterol proteins. This model is the most accepted model as it resembles the fluidity and elasticity of the plasma membrane.