Ultra Structure of Plant Cell 1

7/28/2019 Ultra Structure of Plant Cell 1

1/18

Ultra structure ofplant cell


2/18

Plant cells are eukaryotic cells.

Plant cell contains cytoplasm and nucleus.

Rough and smooth endoplasmic reticulum spreadthroughout the cytoplasm.

It also contains Golgi bodies and mitochondria.


3/18

Cell wall The plant cell wall consists of several layers.

Cell wall is made up of cellulose fibres.

Layers of cellulose fibres are held together by

hemicelluloses, pectin and lignin There are mainly three layers in the cell wall-

middle lamella

primary cell wall

secondary cell wall-


4/18

MIDDLE LAMELLA It is the first layer to form when a plant cell divides intotwo new cells. It is made largely of pectic compounds and proteins. This helps to hold cell walls of neighbouring cellstogether.PRIMARY CELL WALL Formed after the middle lamella. Consist of a rigid skeleton of cellulose micro fibrilsarranged randomly.SECONDARY CELL WALL Formed after cell enlargement is completed. It is made of cellulose, hemicelluloses and lignin.Cellulose is arranged in parallel rows.


5/18


6/18

Functions of cell wall Maintain the structure of the cell.

Path way for the exchange of materials.

Give protection from mechanical injury

and pathogens.

Gives structural support and protection.

Act as a pressure vessel, preventing overexpansion when water enters the cell


7/18

Chloroplast They are large organelles.

Biconvex shape .

Formed from an unspecialized stem cell called

leucoplast. Surrounded by an envelope.

Outer and inner phospholipid membrane.

Most chloroplasts occur in the mesophyll cells ofthe leaves.


8/18

The material within the chloroplast is stroma.

Stroma contain small DNA and ribosomes.

Flattened disc shaped photosynthetic site calledthylakoids are present within the stroma.

Thylakoids are arranged in stalks called grana.


9/18

Functions of chloroplast It is the site of photosynthesis in plants.

Chlorophyll pigments are found in the

thylakoid membrane .

Chlorophyll pigments trap energy from

the sunlight.


10/18

Amyloplast Colourless plastids and membrane bound

organelles in which starch grains are stored.

Responsible for the synthesis and storage of starch

granules.(amylopectin)

Converts starch back into sugars.

Present in large numbers in fruits and underground

storage tissue.

They can change into chloroplast


11/18

Vacuole

Membrane bound and fluid filled space inside the

cytoplasm.

Vacuole is a permanent structure in plant cell.

It is filled with cell sap ( a solution of various

substances in water).

This causes the water to move into the cell by

osmosis.

Keeps the cell turgid and the whole plant upright.

Reduces the diffusion distance by pushing the

organelles towards the periphery.


12/18

Maintaining plant cell shape.

Used for the storage of different substances like

betacyanin pigment in beet root,

proteins in the cells of seeds and fruits,

lytic enzymes

waste products and chemicals (digitalis, a poison in foxgloves)


13/18

Tonoplast Vacuole of the plant cell is surrounded

by a membrane called tonoplast. It separates the vacuolar content from

the cytoplasmic content. Composed of partially permeable

membrane. Made up of phospholipid bilayer andproteins.


14/18

Plasmodesmata Cytoplasmic bridges between the cells. These are narrow fluid filled channels. Intracellular exchange of materials

occur through these channels. The inter connected cytoplasm of the

cell is called symplast.


15/18

These are formed when portions of ER are trapped

between the middle lamella.


16/18

Pits At some places the cell wall is thin because only

the first layer of the cellulose is deposited.

These areas are called pits.

Each pit has a pit chamber and a pit membrane.

Pits are of two types- simple and bordered pits.


17/18

Simple pit

There is no secondary wall in the simple pit.

Width is uniform.

Bordered pit

Secondary wall overhangs the pit.

Width is not uniform.

Function :- cell to cell communication


18/18

ComparisonAnimal cell Differences Plant cell

Do not have fixed

shape

Shape Have fixed shape

Absent Cell wall Present

Small and

temporary

Vacuole Very large and

permanent

Absent Chloroplast Present

Glycogen Food storage Starch

Present Centriole Absent

Documents

Ultra Structure of Plant Cell 1