Cell: The Unit of Life

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The middle lamella is a layer containing calcium pectate which glues

the neighbouring cells together. Cell wall and middle lamellae may be

traversed by plasmodesmata. It connects the cytoplasm of neighbouring

cells.

(AIPMT 2009)

Functions:

It gives shape to the cell.

It protects the cell from mechanical damage & infection.

It helps in cell-to-cell interaction.

It acts as barrier to undesirable macromolecules.

3 Endomembrane system

While each of the membranous

organelle is distinct in terms

of its structure and function,

many of these are considered

together as an endomembrane

system because their functions

are coordinated.

These are a network of tiny

tubular structures scattered in the

cytoplasm.

Endomembrane system includes

endoplasmic

reticulum

(ER),

golgi complex, lysosomes and

vacuoles.

ËÑDØPLÅSMÏÇ RËTÏÇÜLÜM ÏS ØF 2 TÝPËS:



Rough endoplasmic reticulum (RER) : Bear ribosomes on their surface.

RER is frequently observed in the cells actively involved in protein synthesis

and secretion. They extend to the outer membrane of the nucleus



Smooth endoplasmic reticulum (SER): Ribosomes are absent. SER is

the major site for synthesis of lipid and steroids In animal cells lipid-like

steroidal hormones are synthesized in SER

Smooth endoplasmic

Reticulum

Rough endoplasmic

Reticulum

Nucleus

Ribosomes