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Cell : The Unit of Life

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Descrbe  cilia or flagella.

Cilia and flagella are hair-like outgrowths of the cell membrane. Clia are smaller structures while the flagella are longer. They are formed basal bodies which are centriole-like structures. Both help in movement of cell. The cilium and flagellum are covered with plasma membrane. They have a core called axoneme which has nine pairs of doublets of radially arranged peripheral microtubules and a pair of centrally located microtubules. This arrangemt of microtubules is calld 9+2 array. The central tubules are covered by a sheath and are connected to each other. The sheath is connected to one of the tubules of the peripheral doublet by a radial spoke. There ate nine radial spokes in total. The linkers connect the doublets to each other.

State one difference between gram positive and gram negative bacteria.

Gram positive bacteria retains the gram stain whereas the Gram negative bacteria does not.

Who reported that the cell had an outer layer which is known as plasma membrane today?

Theodore Schwann

What are receptor molecules ?

Receptor molecules are specific proteins in the cell's plasma membrane that receive chemical signals from outside the cell. When such chemical signals bind to a receptor, they cause some form of cellular response.

What is the function of contractile vacuole in amoeba?

Excretion.

Who concluded, “Cells are the ultimate units forming the structure of all plant tissues”?

Mathias Schleiden.

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