Cell walls and extracellular matrix

Bactertial cell wall. eukaryotic cell wall. extracellular matrix.
gram positive and gram negative cell wall

1. BY:- VISHAL PANCHAL 19081564006 Class Roll No. - 4609 B.Sc (HONS.)MICROBIOLOGY, 1 ST YEAR CELL WALLS AND EXTRACELLULAR MATRIX

2. Cell Wall Bacterial Cell Wall 1. Gram Negative Cell Wall 2. Gram Positive Cell Wall Eukaryotic Cell Wall 1. Fungal Cell Wall 2. Plant Cell Wall Extracellular Matrix 1. Collagen 2. Elastin 3. Glycoaminoglycans(GAGs) 4. Proteoglycans 5. Fibronectin 6. Laminins CONTENTS

3. Cell wall was first observed and named simply as a “ wall ” by Robert Hooke in 1665 . In 1804, Karl Rudolp hi and J.H.F. Link proved that cells have independent cell walls. A cell wall is a structural layer that surrounds types of cells, situated outside the cell membrane. It can be tough, flexible and rigid which provides cell with both structural support and protection. CELL WALL

4. On the basis of chemical composition of cell wall there are three types of cell wall: 1) Bacterial Cell Wall: made up of Mucopeptide and Muramic acid. 2) Cell wall of Fungi: made up of Chitin . 3) Plant Cell wall: made up of Cellulose .

5. Major component is Peptidoglycan(strong shell). Gram negative bacteria: thin peptidoglycan layer(thin cell wall). Gram positive bacteria: thick peptidoglycan layer(thick cell wall). Archeal cell wall lacks peptidoglycan. It is composed of pseudopeptidoglycan, sulfated polysaccharides, glycoprotiens. BACTERIAL CELL WALL

6. Multi layered and more complex than gram positive cell walls. Peptidoglycan of gram negative bacteria is thin comprises only 10% or less of cell wall. Outer membrane lies outside the thin peptidoglycan layer. Most abundant protein is Braun’s lipoprotein. Gram Negative Cell Wall

7. Usually thick, homogenous, composed mainly of peptidoglycan. It accounts 50- 90% of the dry weight of the cell wall. Contain large amount of teichoic acids. Gram Positive Cell Wall

8. Developed by Christian Gram in 1884. Gram Staining https://www.youtube.com/watch?v=sxa46xKfIOY

9. Click on this video link below for a better understanding of the procedure of gram staining technique. https://youtu.be/sxa46xKfIOY

10. Peptidoglycan ,also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the cell membrane of most bacteria forming cell wall. The sugars component consist of alternating residues of β -(1,4) linked N- acetyl glucosamine and N-acetylmuramic acid. These subunits which are related to glucose in their structure are covalently joined to one another to form glycan chains. Attached to the N- acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross- linked to the peptide chain of another strand forming the peptidoglycan. Peptidoglycan

11. Structure of Peptidoglycan

12. Composed of Chitin(polysaccharide)in fungi and Cellulose(polymer)in plants. Both cellulose and chitin shows β -1,4 linkage . EUKARYOTIC CELL WALL

13. The cell wall is made up of : 1.Chitin (polymers of acetylated amino sugar N- acetylglucosamine ) 2.Glucans 3.Proteins Glucan and Chitin are components of the primary wall. Proteins are components of the secondary wall. Other components include chitosan , melanins and lipids Fungal Cell Wall

14. Structure of Fungal Cell Wall Sec. Cell wall Pri . Cell wall

15. The plant cell wall composed of : 1.The Middle Lamella 2.The Primary Cell Wall 3.The Secondary Cell Wall 4.The Tertiary Cell Wall Plant Cell Wall

16. Middle lamella – first formed from cell plate during cytokinesis. Primary cell wall - composed of cellulose fibrils, produced at plasma membrane by cellulose synthase complex. Microfibrils – held by hydrogen bonds(tensile strength). Secondary cell wall – constructed between plasma membrane and primary wall. Plasmodesmata – interconnecting channels of cytoplasm that connect protoplasts. Formation

17. Middle Lamella It is present between two adjacent cells. It is situated outside primary cell wall and is made up of calcium and magnesium pectate . It acts as cement which holds the adjacent cells together.

18. 2. Primary Cell Wall It is formed after the middle lamella. A thin, flexible and extensible layer. It is capable of growth and expansion. The backbone of primary cell wall is formed by the cellulose fibrils. The matrix is composed of hemicellulose, pectin compounds, lipids, structural proteins. Hemicelluloses are highly branched polysaccharides that are H-bonded to cellulose microfibrils into a tough fiber, which is responsible for the mechanical strength of plant cell wall.

19. The cellulose microfibrils and hemicelluloses are embedded in a gel-like matrix formed by pectins , which are branched polysaccharides containing a large number of negatively-charged galacturonic acid residues. Because of these multiple negative charges, pectins bind positively-charged ions(such as Ca 2+ )and trap water molecules to form gels.

20. 3. Secondary Cell Wall It is extremely rigid and provides strength. It is not found in all cell types. It consists of three layers known as S1(outer),S2(middle) and S3(inner). It is composed of cellulose, hemicellulose and lignin. Lignin is a complex polymer of hydrophobic phenolic residues, which inserts into the spaces between the other polymers. Lignin is responsible for much of the strength and density of wood.

21. 4. Tertiary Cell Wall Tertiary cell wall is deposited in few cells. It is considered to be dry residue of protoplast . Besides cellulose and hemi-cellulose, xylan is also present. Plasmodesmata Plasmodesmata are protoplasmic strands that connect the protoplasts of neighboring cells. Diameter is 40-50 nm.

22. A brief explanation about cell wall.

23. Many animal cells are intrinsically linked to other cells and to the extracellular matrix (ECM). Cell surface molecules bind to other cells, or to other components of the ECM. They also play a role in mutual recognition of similar cell types. Bone and cartilage are mostly ECM plus a very few cells. Connective tissue that surrounds glands and blood vessels, is a gelatinous matrix containing many fibroblast cells. EXTRACELLULAR MATRIX

24. The ECM contains 3 classes of molecules: Structural proteins ( collagens and elastins ) Protein-polysaccharide complexes to embed the structural proteins ( proteoglycans ) Adhesive glycoproteins to attach cells to matrix ( fibronectins and laminins ).

25. Most abundant protein in animals-25% Secreted mostly by connective tissue cell and in small quantity by other cell Collagen contributes to the stability of tissues and organs. It maintains their structural integrity. It has great tensile strength. The main component of fascia, cartilage, ligaments, tendons, bone and skin. Plays an important role in cell differentiation, polarity, movement. Plays an important role in tissue and organ development . Collegen

26. Human genome contains 42 distinct a-chain genes (42 can undergo different combinations Less than 40 types of collagen found so far Triple helix of 3 α-chains α-chain structure Gly-X-Y repeats in a left handed turn X frequently a proline Y frequently a hydroxylysine or hydroxyproline (mostly) Proline and hydroxyproline makes the chain more rigid The glycine because of its small nature is able to be accommodated in the crowded helix Collegen Structure

27. Prolyl hydroxylase

28. Several other types of collagen do not form fibrils but play distinct roles in various kinds of extracellular matrices. Type-IV collagen do not form fibrils but form a mesh-like network. Basal lamina form from different types of collagen, primarily type-IV collagen, but also type VI and XVIII, all of which are network-forming collagens.

29. Elastin is a major protein component of tissues that require elasticity such as arteries, lungs, bladder, skin and elastic ligaments and cartilage. It is composed of soluble tropoelastin protein containing primarily glycine and valine and modified alanine and proline residues. It is secreted by connective tissue cells as soluble tropoelastin into EC matrix. Forms cross linkages with each other- catalysed by lysil oxidase Forms an extensive network of elastin fibres and sheets Elastin fibres associate with microfibrils made up of glycoproteins including fibrillin Elastin

30. Polypeptide chains are cross-linked together to form rubberlike, elastic fibers. Each elastin molecule uncoils into a more extended conformation when the fiber is stretched and will recoil spontaneously as soon as the stretching force is relaxed

31. Many different genetic types Triple helix (Gly-X-Y)n repeating structure Presence of hydroxylysine Carbohydrate-containing Intramolecular aldol cross-links Presence of extension peptides during bio- synthesis One genetic type No triple helix; random coil conformations permitting stretching No (Gly-X-Y)n repeating structure No hydroxylysine, No carbohydrate Intramolecular desmosine cross-links No extension peptides present during biosynthesis Collagen Elastin

32. Unbranched polysaccharide chains composed of repeating dissacharide units. Negatively charged under physiological conditions (due to the occurrence of sulfate and uronic acid groups) Disaccharide subunits are: 1. Uronic acid D- glucuronic acid or L- iduronic acid 2. Aminosugar N- acetylglucosamin (GlcNAc) or N- acetylgalactosamin (GalNAc) Glycoaminoglycans (GAGs)

33. Amino sugars and uronic acids are the most common building blocks of the glycosaminoglycans. Amino sugars : -OH at C-2 is replaced by an amino group. This amino group is most often acetylated and sometimes sulfated. Uronic acids : C-6 of the hexose is oxidized to a carboxyl group. Common sulfated GAGs are dermatan sulfate, chondroitin sulfate, keratin sulfate, and haparan sulfate. (Exception: Hyaluronan is a non-sulfated GAG and the only GAG that occurs as a single long polysaccharide chain)

34. Proteins linked covalently to glycosaminoglycans (GAGs). Carbohydrates(polysaccharides) make up about 95% of its weight. Proteins bound covalently to GAGs are called core proteins. Many have been classified; they vary in tissue of origin, function, core protein types. Examples include aggrecans, syndecan, betaglycan, serglycan. Proteoglycans

35. A number of proteoglycans interact with hyaluronan to form large complexes in the ECM. A well-characterized example is aggrecan , the major proteoglycan of cartilage.

36. Principal adhesion protein of connective tissues. Dimeric glycoprotein consisting of two polypeptide chains , each containing nearly 2500 amino acids. Has binding sites for both collagen and GAGs so it cross-links these matrix components. Attached to cell membrane by membrane-spanning receptor – integrin . Derived by alternative splicing of the mRNA of a single gene. Fibronectin

37. Laminins are cross- or T-shaped heterotrimers of α , β ,and γ subunits, which are the products of five α genes, three β genes, and three γ genes. Principal components of basal laminae. Like type-IV collagen, laminins can self-assemble into meshlike networks. Laminins are tightly associated with another adhesion protein, called nidogen, which also binds to type-IV collagen. Laminin, nidogen, collagen, and the proteoglycans form cross-linked networks within basal laminae. Laminins

38. A brief explanation about extracellular matrix .