Question

Various types of transport mechanisms are needed to fulfil the mineral requirements of a plant. Why are they not fulfilled by diffusion alone?

Answer 1

Diffusion

Diffusion is the movement of particles from their high concentration to the lower concentrations. Small uncharged molecules can easily diffuse across the biological membrane.

Plasma membrane

The plasma membrane is a bilayer lipid membrane allowing only lipid soluble substances to pass through easily.


Ion transport

* The charged ions (examples of sodium ion and chloride ions) or polar molecules like water are not able to cross the lipid bilayer of the biological membrane.

* Transport of these ions is facilitated by transport proteins embedded in the membrane.

* The transport proteins provide binding sites to bind the specific molecule or ion to be transported. It binds and transports the molecule or ion across the membrane.

Therefore various types of transport mechanisms like active transport, facilitate diffusion( using carrier proteins, channel proteins ( like aquaporins), gated channels ) are needed to fulfil the mineral requirements of a plant.