Modifications of Plasma Membrane to do Various Activites

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To fulfill lots of activity, Plasma Membrane changes itself by means of various ways into a special structure. This is known as Modifications of Plasma Membrane. The plasma membrane shows different kinds of modifications in different types of cells.  Foldings , intercellular junctions and extracellular coats are common modifications of plasma membrane.

also read : Botanical Name and Family of the Plant with Local Name

1.  Foldings

The plasma membrane bends inwards and outwards many times to form foldings, which are found in many forms. Folding involves two types of structure formation –

a.  Infolds  or  Invaginations

  • Infolds are made, when plasma membrane bends inwards direction.
  • By the infolds activity pores , endocytic vesicles and mesosomes like structures are formed.
    • Endocytic vesicles takes the solid & liquid food substances from external atmosphere and release them in the cell.
    • Mesosomes are founds in bacteria, and it increases the functional area of activity.
cell containing Mesosomes
Mesosome

b.  Outfolds  or  Evaginations

  • When The plasma membrane bends outwards direction, outfolds are made.
  • These are found in the form of microvilli, ciliated and flagellated.

    Microvilli Formation

2.  Intercellular Junctions

In animal cells, narrow spaces are found between the two adjacent cells , called as intercellular spaces or intercellular junctions. These spaces are filled with tissue fluids. These are connecting medium of two adjacent cells. These are as following types –

a.  Intercellular Bridges

  • The micro protrusions like structures emerging from the cell membrane of two adjacent cells are called intercellular bridges.
  • The main function is to facilitate the exchange the substances between two adjacent cells.


    Intercellular Bridge

b.  Desmosomes

  • In it the globular patches of plasma membrane joints with proteins.
  • A protein plate is founds in the inner surface of cell membrane which provides the mechanical support to the cell.

    Desmosomes

  • Many fibrils are present on this protein plate, referred as tonofibrils.
  • These tonofibrils are scattered in the cell.
  • Desmosomes are commonly found in epithelial cells and binds the adjacent cells 

c.  Tight Junctions or  Occluding Junctions

  • Between two epithelial cell tight junction make a layer like structure.
  • This layer acts as a selective barrier for the fluids present on both side.
Tight Junction

d.  Communicating Junctions

The main function of communicating junctions is to transmit chemical and electrical ions. chemical synapsis and gap junctions are commonly found in animal cells while plasmodesmata is found in plant cells. 

read more : Sickle Cell Anaeamia : Genic Mendelian Abnormalities

i .  Gap Junctions

  • Gap Junctions are founds in animals.
  • Few special proteins are responsible for the connection and transmission between two cells.
  • These proteins are referred as connexon which helps to make wide gaps in cells measuring 2 – 4 nm.
  • Each connexon is a tunnel-like structure surrounded by six identical protein subunits.
  • These proteins allow tiny molecules and ions to pass from one cell to another without entering any gap.
Gap Junction

ii.  Plasmodesmata

  • Plasmodesmata are found in plants cell.
  • Few micro and intercellular tubular passages are present in cell wall and middle lamella.
  • Through these passages the cytoplasm , endoplasmic reticulum and cell membranes are connected with each other.
  • Water , solutes, few proteins and few RNAa are flows through these passages from one cell to another cell.
  • Plasmodesmata are two types : primary plasmodesmata – forms during the cell division and secondary plasmodesmata – forms between mature cells.

Plasmodesmata

3.  Extracellular Coats

Extracellular coats are protective layers surrounding cells or cellular structures.

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