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.
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