Question

How does transportation of substances take place through plasma membrane?

Answer 1

• The plasma membrane or cell membrane is a lipid bilayer membrane in which proteins are embedded that separates the cytoplasm of the cell from the extracellular spaces.
• It is selectively permeable that regulates the transportation of molecules.
• The transportation of molecules across the membrane can be active or passive.

1) Active transportation- is the movement of molecules (ions, glucose and amino acids) across the membrane against the concentration gradient.

• It requires cellular energy.
• The protein molecules embedded within the membrane act as channels through which molecules can pass.
• These proteins are called carriers i.e, the molecule attaches to the carrier protein which then transports that molecule into the cell.
  

2) Passive transportation- is the movement of molecular substances across cell membranes along the concentration gradient without any energy.

• They are of three types:-

a) Diffusion- is the movement of molecules from the area highly concentrated to an area where the molecules are less concentrated.

b) Osmosis- is the diffusion of water molecules.

c) Filtration- is the movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system.