What is Amoeboid Movements ? Functions

Amoeboid movement is the most basic type of movement and perhaps the least understood. it refers to the characteristic crawling movement of some protists( Protozoa), Slime moulds and somewhat break cell such as white blood cells.

This crawling movement is also seen in the vertebrate kupffer cells in the liver ‚metastasizing cancerous cells, in animal cell in tissue culture, in the cells of the developing animal embryo and in any other cell where the movement is effected by p cytoplasmic streaming,Constant changes in the cell shape and extension of pseudopodia of. these changes can easily be seen under the microscope.

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Amoe­boid Movement

Amoe­boid move­ment begins in a Cell or a sin­gle celled organ­isms like Amoe­ba by exten­sion ‚of an arm like struc­ture called the pseu­do podi­um, In the required direc­tion in to which the cyto­plasm of a sin­gle cell or Sin­gle celled organ­isms flows. 

the new­ly formed pseu­do podi­um enlarge and the cell final­ly occu­pies the space where pre­vi­ous­ly the news to the podi­umpodi­um had begun to form.

There are two regions in the cytoplasm of the Amoeba under the light microscope which are as follows:

  • i) The cen­tral Endo­plas­mic of gran­u­lar plas­ma which is flu­id in nature and is also called sole cytoplasm.

It con­tains gran­u­lar inclu­sion and mem­bra­nous par­ti­cles that are in con­stant ran­dom motion

  • ii) The periph­er­al clear gel like part of the cyto­plasm called ecto­plasm or hyaloplasm.

The ecto­plasm con­tains three-dimen­sion­al net­work of actin and myosin fil­a­ment (actin and myosin are found in all Eukary­ot­ic cell)

The gel like region appar­ent­ly decides the shape of the pseu­do podi­um and may trans­mit ten­sion from the rea­son of cel­lu­lar con­trac­tion to the sides of con­tact with the substratum.

Loco­mo­tion in Amoe­ba is caused by con­tin­u­ous assem­bly and dis­as­sem­bly of the actin and myosin con­tain­ing complexes.The ecto­plas­ma at the front and becomes thin caus­ing a pseu­do podi­um to bulge forward.The rear end of the Amoe­ba con­tracts and push­es the stream­ing endo­plasm into the elon­gat­ing psedupodium .

In the region near the tip of pseu­do podi­um the pro­tein act­ing poly­meris­es to form a fil­a­men­tous net­work by the crosslink­ing of the actin pro­tein and myosin protein.

The crosslink­ing of the actin pro­tein and myosin pro­tein cause the fil­a­men­tous net­work to con­tract pulling the cell in the direc­tion of the pseu­do podium.

As a cell moves new pseu­do podi­um forms in the direc­tion of the move­ment, While the pos­te­ri­or part con­tract and are with­drawn. it is not known with cer­tain­ty how the exten­sion and retrac­tion of the pseu­do podi­um takes place.

It appears that there is a con­ver­sion of the cyto­plasm from flu­id like sol state to the semi sol­id gel state.

The ener­gy required for loco­mo­tion comes from ATP. it is still not known how amoe­boid move­ment is con­trol or reg­u­lat­ed. how­ev­er it is known that Amoe­ba can­not extend their pseudopo­dia in all direc­tion simul­ta­ne­ous­ly if they could they would be ripped apart! It is known how­ev­er that the abil­i­ty of many actin bind­ing pro­tein to cross linked to actin is strong­ly depen­dent or cal­ci­um ion Con­cen­tra­tion and ph.

Thus cal­ci­um and hydro­gen ion and reg­u­late the sol to gel transition.In low molar con­cen­tra­tion of cal­ci­um ion and when pH is low­ered to 6.8 the cyto­plasm of the amoe­ba begins to set as a gel while solu­tion of the gel starts when pH of cal­ci­um and is raised.

Study sug­gest that pro­teins such as gel­solin or villin are respon­si­ble for gel to SOL tran­si­tion because these pro­teins frag­ment act in the pres­ence of micro­mo­lar of free cal­ci­um ion.

It has been sug­gest­ed that direct­ed growth of pseudopo­dia is due to dif­fer­ence in cal­ci­um Ion or hydro­gen ion con­cen­tra­tion among var­i­ous regions of the cyto­plasm. whether this is the case how­ev­er remains to be determined.

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