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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
Describe the types and functions of endoplasmic reticulum.

Endoplasmic reticulum is of following two types:

A. Smooth endoplasmic reticulum - does not have ribosome.
B. Rough endoplasmic reticulum - has ribosomes attached to it.

A. Functions of smooth endoplasmic reticulum :

1. It is especially prominent in cells which are not involved in the synthesis of lipids.

2. It is involved in the synthesis of Golgi complex, lysosmoes and microbodies.

B. Functions of rough endoplasmic reticulum:

1. It is primarily involved in protein synthesis owing to the presence of ribosomes.

2. Packaging. The proteins manufactured in ribosomes are packed in RER. They are processed and packed in vesicles which are pinched off from RER.

3. Formation of glycoproteins. The carbohydrates and proteins are linked in RER to form glycoproteins.

4. Helps in the formation of  nuclear envelops.

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

Theodore Schwann

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

Mathias Schleiden.

What is the function of contractile vacuole in amoeba?

Excretion.

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.

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