WHAT IS CELL MEMBRANE OR PLASMA MEMBRANE

 CELL MEMBRANE OR PLASMA MEMBRANE

OUTERMOST BOUNDARY;

✦PLASMA MEMBRANE OR CELL MEMBRANE IS THE OUTERMOST

 BOUNDARY OF ALL CELL.

COMPOSED OF;

✦CELL MEMBRANE IS CHEMICALLY COMPOSED OF LIPIDS AND 

PROTEINS;60-80% ARE PROTEINS, WHILE 20-40% ARE LIPIDS. IN 

ADDITION THERE IS A SMALL QUANTITY OF CARBOHYDRATES.

FUNCTION;

✦CELL MEMBRANE FUNCTION AS A SEMI-PERMEABLE MEMBRANE,

  ALLOWING A VERY FEW  MOLECULES ACROSS IT WHILE FENCING 

 THE MAJORITY OF CHEMICALS INSIDE CELL.IN THIS WAY CELL

  MAINTAINS THE INTERNAL COMPOSITION OF CELL.

STRUCTURE;

✦MANY BIOLOGIST CONTRIBUTED TO ESTABLISH THE STRUCTURAL

ORGANIZATION OF CELL MEMBRANE. 

UNIT MEMBRANE;

✦IT WAS PROPOSED EARLIER THAT CELL MEMBRANE IS COMPOSED OF

LIPID BILAYER SANDWICHED BETWEEN INNER AND OUTER LAYERS OF

PROTEIN. THIS BASIC STRUCTURE IS CALLED THE UNIT MEMBRANE AND

PRESENT IN ALL CELLULAR ORGANELLE.

MODERN TECHNOLOGY OR CHEMICAL ANALYSIS;

✦THE MODERN TECHNOLOGY HAS REVEALED THAT LIPID BILAYERS ARE 

NOT SANDWICHED BETWEEN TWO PROTEIN LAYERS.

FLUID MOSAIC MODEL;

✦THE PROTEIN LAYERS ARE NOT CONTINUOUS AND CONFINED TO THE

 SURFACE OF A MEMBRANE BUT ARE EMBEDDED IN LIPIDS LAYERS IN

 MOSAIC MANNER. THIS DISCOVERY LED TO THE PROPOSAL OF FLUID

 MOSAIC MODEL.

CHARGED PORES;

✦CELL MEMBRANE ALSO CONTAIN CHARGED PORES THROUGH WHICH 

   MOVEMENT OF MATERIALS TAKES PLACE, BOTH BY ACTIVE AND PASSIVE

   TRANSPORT.

DIFFERENTIALLY OR SELECTIVELY PERMEABLE MEMBRANE;  

✦TRANSPORT OF MATERIAL IS ONE OF THE VITAL ROLES IT PLAY FOR THE

  CELL. IT OFFERS A BARRIER BETWEEN CELL CONTENTS AND THEIR

  ENVIRONMENT, ALLOWING ONLY SELECTIVE SUBSTANCES TO PASS 

  THROUGH IT, THUS IT IS KNOWN AS DIFFERENTIALLY PERMEABLE OR

 SELECTIVELY PERMEABLE MEMBRANE.

LIPID SOLUBLE PARTICLES;

✦THE SUBSTANCES WHICH ARE LIPID SOLUBLE CROSS IT MORE EASILY 

  THAN OTHERS, THEREFORE, IT REGULATES THE FLOW OF MATERIALS

  AND IONS,TO MAINTAIN A DEFINITE GRADIENT.

SMALL GAS MOLECULES AND IONS; 

✦MANY SMALL GAS MOLECULES, WATER, GLUCOSE ETC. BEING NEURA

  CAN EASILY CROSS WHILE IONS, BEING CHARGED PARTICLES, HAVE

  SOME DIFFICULTY IN CROSSING.

TAKE IN MATERIAL;

✦IN MANY ANIMAL CELLS, THE CELL MEMBRANE HELPS TO TAKE IN 

  MATERIALS BY INFOLDING IN THE FORM OF VACUOLES. THIS TYPE OF

  INTAKE IS KNOWN AS ENDOCYTOSIS.

TYPES OF ENDOCYTOSIS;

➤PHAGOCYTOSIS;

✦TO ENGULF SOLID PARTICLES.

➤PINOCYTOSIS;

✦TO TAKE IN LIQUID MATERIAL.