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Cell : The Unit of Life

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Class 10 Class 12
Discuss the types of endoplasmic reticulum

Endoplasmic reticulum depending upon the presence or absence of the ribosomes :

1. Smooth endoplasmic reticulum (agrannular form). The outer surface of the membranes of such endoplasmic reticulum is smooth and does not bear ribosomes. The smooth endoplasmic reticulum is the major site for synthesis of lipid. In animal cells lipid-like steroidal hormones are synthesised in SER.

2. Rough endoplasmic reticulum (grannular from). bears ribosomes on its surface. Due to the presence of ribosomes the outer surface appears to be grannular or rough. Rough endoplasmic is continuos with the outer membrane of the nucleus. It is found in cells actively engaged in protein synthesis e.g. cells of pancreas, plasma cells, liver cells, goblet cells etc.

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.

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.

State one difference between gram positive and gram negative bacteria.

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

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