Page 1
Cell wall
Institute of Lifelong Learning, University of Delhi
Subject: Cell Biology
Lesson: Cell Wall
Lesson Developer: Rina Majumdar
College/ Department: Maitreyi college, University of Delhi
Page 2
Cell wall
Institute of Lifelong Learning, University of Delhi
Subject: Cell Biology
Lesson: Cell Wall
Lesson Developer: Rina Majumdar
College/ Department: Maitreyi college, University of Delhi
Cell wall
Institute of Lifelong Learning, University of Delhi 1
Table of Contents
Chapter: Cell wall
? Introduction
? Importance
? Chemistry of the cell wall
? Bacterial cell wall
? Gram positive and negative bacteria
? Cell wall in archea
? Eukaryotic cell wall
o Wall layers
? Middle lamella
? Primary cell wall
? Secondary cell wall
o Composition of the cell wall
? Cellulose
? Hemicellulose
? Pectin
? Glycoprotein
? Lignin
? Cutin, suberin and waxes
? Algal cell wall
? Fungal cell wall
? Formation of cell wall
? Summary
? Exercise/ Practice
? Glossary
? References/ Bibliography/ Further Reading
Page 3
Cell wall
Institute of Lifelong Learning, University of Delhi
Subject: Cell Biology
Lesson: Cell Wall
Lesson Developer: Rina Majumdar
College/ Department: Maitreyi college, University of Delhi
Cell wall
Institute of Lifelong Learning, University of Delhi 1
Table of Contents
Chapter: Cell wall
? Introduction
? Importance
? Chemistry of the cell wall
? Bacterial cell wall
? Gram positive and negative bacteria
? Cell wall in archea
? Eukaryotic cell wall
o Wall layers
? Middle lamella
? Primary cell wall
? Secondary cell wall
o Composition of the cell wall
? Cellulose
? Hemicellulose
? Pectin
? Glycoprotein
? Lignin
? Cutin, suberin and waxes
? Algal cell wall
? Fungal cell wall
? Formation of cell wall
? Summary
? Exercise/ Practice
? Glossary
? References/ Bibliography/ Further Reading
Cell wall
Institute of Lifelong Learning, University of Delhi 2
Introduction
Cell wall is one of the unique features in the plant cell that distinguishes it from the animal
cell. The boundary of each cell in plants is, defined by the cell wall. It is made of insoluble
structural polysaccharide secreted by the cells. The plasma membrane forms the outermost
layer in animal cells where as in plants the plasma membrane lies next to the cell wall,
which provides an elaborate extracellular matrix. Plant cell wall can be modified in response
to changing environmental conditions.
Importance
Cell wall represents the outer covering of a cell, present outside the cell membrane. Cell
wall is present in plants, algae, fungi and bacteria and is absent in animals and protozoans.
It has key role in strengthening, plant growth, cell differentiation, water movement and
defense.
In plants, cell wall not only provides rigidity and strength but also forms a protective home
for the cellular constituents. The definite shape of each plant cell is due to the presence of
cell wall. The intact multicellular plant body is formed due to the cementing together of cell
wall to that of its neighbors. In addition, direct cell-cell communication is possible through
plasmodesmata, which are plasma membrane lined channels of cytoplasm that cross the
cell wall. Besides protective function, cell wall also plays important role in cellular
absorption, secretion, and transport across the cells, and various other functions. Being,
the outermost layer in plant cells , it also plays an important role in cellular defense against
various pathogens. Unlike animal cells, plant cells are, prevented from swelling and
bursting because of osmotic pressure by the presence of cell wall outside. Cell wall also
serves to store carbohydrates that can be broken down by enzymes and used by the cell.
For e.g. the cell walls in endosperm of cereals are rich in glucans and polysaccharides and
nourish the growing embryo during seed germination.
To summarize some of the important functions of cell wall are:
? Gives structural and mechanical support thus determining the overall form and
architecture of the plant
? Gives definite shape to the cell
? Prevents cell from bursting by resisting the turgor pressure from inside the cell.
? Regulates exchange of material through the apopalst
? Determines the growth direction and rate
? Protection
Page 4
Cell wall
Institute of Lifelong Learning, University of Delhi
Subject: Cell Biology
Lesson: Cell Wall
Lesson Developer: Rina Majumdar
College/ Department: Maitreyi college, University of Delhi
Cell wall
Institute of Lifelong Learning, University of Delhi 1
Table of Contents
Chapter: Cell wall
? Introduction
? Importance
? Chemistry of the cell wall
? Bacterial cell wall
? Gram positive and negative bacteria
? Cell wall in archea
? Eukaryotic cell wall
o Wall layers
? Middle lamella
? Primary cell wall
? Secondary cell wall
o Composition of the cell wall
? Cellulose
? Hemicellulose
? Pectin
? Glycoprotein
? Lignin
? Cutin, suberin and waxes
? Algal cell wall
? Fungal cell wall
? Formation of cell wall
? Summary
? Exercise/ Practice
? Glossary
? References/ Bibliography/ Further Reading
Cell wall
Institute of Lifelong Learning, University of Delhi 2
Introduction
Cell wall is one of the unique features in the plant cell that distinguishes it from the animal
cell. The boundary of each cell in plants is, defined by the cell wall. It is made of insoluble
structural polysaccharide secreted by the cells. The plasma membrane forms the outermost
layer in animal cells where as in plants the plasma membrane lies next to the cell wall,
which provides an elaborate extracellular matrix. Plant cell wall can be modified in response
to changing environmental conditions.
Importance
Cell wall represents the outer covering of a cell, present outside the cell membrane. Cell
wall is present in plants, algae, fungi and bacteria and is absent in animals and protozoans.
It has key role in strengthening, plant growth, cell differentiation, water movement and
defense.
In plants, cell wall not only provides rigidity and strength but also forms a protective home
for the cellular constituents. The definite shape of each plant cell is due to the presence of
cell wall. The intact multicellular plant body is formed due to the cementing together of cell
wall to that of its neighbors. In addition, direct cell-cell communication is possible through
plasmodesmata, which are plasma membrane lined channels of cytoplasm that cross the
cell wall. Besides protective function, cell wall also plays important role in cellular
absorption, secretion, and transport across the cells, and various other functions. Being,
the outermost layer in plant cells , it also plays an important role in cellular defense against
various pathogens. Unlike animal cells, plant cells are, prevented from swelling and
bursting because of osmotic pressure by the presence of cell wall outside. Cell wall also
serves to store carbohydrates that can be broken down by enzymes and used by the cell.
For e.g. the cell walls in endosperm of cereals are rich in glucans and polysaccharides and
nourish the growing embryo during seed germination.
To summarize some of the important functions of cell wall are:
? Gives structural and mechanical support thus determining the overall form and
architecture of the plant
? Gives definite shape to the cell
? Prevents cell from bursting by resisting the turgor pressure from inside the cell.
? Regulates exchange of material through the apopalst
? Determines the growth direction and rate
? Protection
Cell wall
Institute of Lifelong Learning, University of Delhi 3
? Cell – cell interaction
? Storage in the form of wall carbohydrates
? Source of biological signaling molecules
Figure: Electron micrographs showing plasmodesmata (arrow) between two adjacent cells
Source: http://pix.botany.org/set14/14-003h_300.jpg
Figure: Diagrammatic representation of Plasmodesmata connecting the two cells via the
apoplastic and symplastic pathways.
Source: http://upload.wikimedia.org/wikibooks/en/0/00/Waterpathwaysthroughrootcells.gif
Chemistry of the cell wall
Chemical composition of the cell wall varies within different biological organisms.
Bacterial cell wall
Page 5
Cell wall
Institute of Lifelong Learning, University of Delhi
Subject: Cell Biology
Lesson: Cell Wall
Lesson Developer: Rina Majumdar
College/ Department: Maitreyi college, University of Delhi
Cell wall
Institute of Lifelong Learning, University of Delhi 1
Table of Contents
Chapter: Cell wall
? Introduction
? Importance
? Chemistry of the cell wall
? Bacterial cell wall
? Gram positive and negative bacteria
? Cell wall in archea
? Eukaryotic cell wall
o Wall layers
? Middle lamella
? Primary cell wall
? Secondary cell wall
o Composition of the cell wall
? Cellulose
? Hemicellulose
? Pectin
? Glycoprotein
? Lignin
? Cutin, suberin and waxes
? Algal cell wall
? Fungal cell wall
? Formation of cell wall
? Summary
? Exercise/ Practice
? Glossary
? References/ Bibliography/ Further Reading
Cell wall
Institute of Lifelong Learning, University of Delhi 2
Introduction
Cell wall is one of the unique features in the plant cell that distinguishes it from the animal
cell. The boundary of each cell in plants is, defined by the cell wall. It is made of insoluble
structural polysaccharide secreted by the cells. The plasma membrane forms the outermost
layer in animal cells where as in plants the plasma membrane lies next to the cell wall,
which provides an elaborate extracellular matrix. Plant cell wall can be modified in response
to changing environmental conditions.
Importance
Cell wall represents the outer covering of a cell, present outside the cell membrane. Cell
wall is present in plants, algae, fungi and bacteria and is absent in animals and protozoans.
It has key role in strengthening, plant growth, cell differentiation, water movement and
defense.
In plants, cell wall not only provides rigidity and strength but also forms a protective home
for the cellular constituents. The definite shape of each plant cell is due to the presence of
cell wall. The intact multicellular plant body is formed due to the cementing together of cell
wall to that of its neighbors. In addition, direct cell-cell communication is possible through
plasmodesmata, which are plasma membrane lined channels of cytoplasm that cross the
cell wall. Besides protective function, cell wall also plays important role in cellular
absorption, secretion, and transport across the cells, and various other functions. Being,
the outermost layer in plant cells , it also plays an important role in cellular defense against
various pathogens. Unlike animal cells, plant cells are, prevented from swelling and
bursting because of osmotic pressure by the presence of cell wall outside. Cell wall also
serves to store carbohydrates that can be broken down by enzymes and used by the cell.
For e.g. the cell walls in endosperm of cereals are rich in glucans and polysaccharides and
nourish the growing embryo during seed germination.
To summarize some of the important functions of cell wall are:
? Gives structural and mechanical support thus determining the overall form and
architecture of the plant
? Gives definite shape to the cell
? Prevents cell from bursting by resisting the turgor pressure from inside the cell.
? Regulates exchange of material through the apopalst
? Determines the growth direction and rate
? Protection
Cell wall
Institute of Lifelong Learning, University of Delhi 3
? Cell – cell interaction
? Storage in the form of wall carbohydrates
? Source of biological signaling molecules
Figure: Electron micrographs showing plasmodesmata (arrow) between two adjacent cells
Source: http://pix.botany.org/set14/14-003h_300.jpg
Figure: Diagrammatic representation of Plasmodesmata connecting the two cells via the
apoplastic and symplastic pathways.
Source: http://upload.wikimedia.org/wikibooks/en/0/00/Waterpathwaysthroughrootcells.gif
Chemistry of the cell wall
Chemical composition of the cell wall varies within different biological organisms.
Bacterial cell wall
Cell wall
Institute of Lifelong Learning, University of Delhi 4
The unicellular prokaryotic bacterial cells are characterized by the presence of cell wall
made up of a unique polymer, found nowhere in other living organisms, known as
Peptidoglycan/ Murein. It is a hetero-polysaccharide consisting of alternating monomers
of N-acetyl glucosamine (NAG) and N-acetyl muramic Acid (NAM) and joined by ß
1 ?4 glycosidic linkage, arranged in parallel chains.
Figure: N-acetyl glucosamine (NAG) and N-acetyl muramic Acid (NAM)
Source: http://www.flickr.com/photos/ajc1/2281351707/
These parallel chains are, cross-linked by tetra-peptide attached to the NAM residues. The
amino acids forming the tetra-peptides vary in different species of bacteria.
Figure: The chains of N-acetyl glucosamine and N-acetyl muramic acid are joined together
by peptide bridges in peptidoglycan
Source: http://upload.wikimedia.org/wikipedia/commons/thumb/2/29/Mureine.svg/271px-
Mureine.svg.png
Also visit: http://classes.midlandstech.edu/carterp/Courses/bio225/chap04/04-
13a_BactCellWall_1.jpg
Gram positive and Gram negative bacteria
Read More