Composition of cell wall, Biology

Assignment Help:

COMPOSITION OF CELL WALL

Cell wall composed of cellulose, hemicellulose, pectin, lignin, cutin & chitin.

Cell wall consists of 3 parts -

1. Matrix

  • Highly cross-linked amorphous gel-like ground substances.
  • Water = 30-60%, forms dispersion medium, hydration.
  • Pectin = 2-8%, heteropolysaccaride, helps in cross-linking, determines hydration of cell wall, elasticity, growth.
  • Hemicellulose = 5-15%,     Lipid = 0.5-3%, Protein = 1-2%

2. Microfibrils

  • Structural elements of cell wall. Provide rigidity of cell wall.
  • In plants microfibrils are formed of cellulose.
  • They are 10-25 mm in thickness, 0.5-0.7 mm in length.
  • Cellulose forms the backbone of the plant cell.
  • Cellulose polymer of b-D-glucose.
  • A cellulose microfibril consists of about 3000 glucose molecules.
  • Many chains of cellulose molecules lie parallel to each other to form the bundles.
  • A bundles of 100 molecules of cellulose forms the one elementary fibril known as the micelle.
  • The 20 micelle when get arraged parallely, form the fibrils of 250Å thick, known as microfibrils.
  • Microfibril forms large size bundle of cellulose fibres to form the macrofibrils. (macrofibril form skeletal of cell wall).
  • Microfibrils are loose & wavy in primary wall.
  • Microfibrils are close & parallel arrangement in secondary wall.
  • The hemicellulose is composed of monosaccharide units like arabinose, xylose, mammose & galactose.
  • The pectin chemically composed of glucuronic and galacturonic acid.
  • The lignin chemically composed of confieryl alcohol.
  • The cutin composed of many fatty acids.
  • In fugal cell wall formed of chitin material.
  • The chitin is a polymer of b (1® 4) acetyl glucosamine.
  • Chitin also occurs in Exoskeleton of Arthropods (insects + crustaceans)
  • Chitin is second most abundant organic material.
  • In bacterial cell wall made up of peptidoglycan mucopeptide (murein).
  • Murein is made of N-acetyl glucosamine, acetyl muramic acid and small peptide chains.
  • i.e. Murein is polymer of NAG and NAM

3. Deposition on the cell wall

(a) Lignin

  • Deposition of lignin on cell wall is called lignification.
  • After lignification cell becomes dead & impermeable to water.
  • It provides hardness to the wall.
  • Lignification commonly occur in seconday cell wall.
  • Lignin is the derivative of cellulose.
  • Lignification developed with evolution of land plants.

(b) Cutin

  • Depostion of cutin is called cutinization.
  • Cutin derivative of lipid. Polymer of Hydroxy fatty acids.
  • Deposition on epidermal cells of leaf.
  • Epidermal layer form a layer "cuticle" outside the cell wall.
  • Formation of cuticle layer is called "Cuticularisation".
  • Cutin reduces the rate of transpiration. (Loss of water in vapour form)

(c) Suberin

  • Deposition of suberin is called Suberization.
  • Suberin derivative of fatty acids. Consists of Phellonic acid and Glycerol.
  • After suberization cell becomes dead and impermeable to water.
  • It occurs in cork cells and endodermal cells.
  • Commercial cork is obtained from Quercus suber (Spanish oak)

(d) Silica

  • Deposition occur in Atropa, Grasses, Equisetum, Diatoms.
  • It provides stiffness to wall. Protects the plants from fungal attack. Irritation to grazing animals.

(e) Nonsiliceous Minerals

  • Deposition of Fe and Cu occurs in aquatic habitat plants, e.g. Chara

(f) Wax

  • Polymer of fatty acid and alcohol.
  • Wax occurs as component of cuticle and surface bloom.
  • Water repellent and control transpiration.

Related Discussions:- Composition of cell wall

Explain type 2 diabetes mellitus, Q. Explain Type 2 Diabetes Mellitus? ...

Q. Explain Type 2 Diabetes Mellitus? It is the most common form of diabetes accounting for 90-95% of patients with diabetes. Type 2 Diabetes Mellitus was previously called as N

Make a sketch of a petroleum trap, Create a sketch of a petroleum trap. Wri...

Create a sketch of a petroleum trap. Write a history for how it came to the present (sketched) form following the rules of logical deduction.

Kin selection, While explaining the concept of natural selection, we have s...

While explaining the concept of natural selection, we have stressed the fact that natural selection is synonymous with differential or non-random reproduction. Natural selection ai

Explain shannon-wiener index, Q. Explain Shannon-Wiener index? This div...

Q. Explain Shannon-Wiener index? This diversity measure is based on information theory of measure of order (or disorder) within a particular system. For our uses, this order co

Massaging and tumbling techniques in meat products, M a s s a g i n ...

M a s s a g i n g and tumbling techniques To improve the desirable characteristics of meat products massaging and tumbling techniques were developed. Massaging involves

Altered protein metabolism - metabolic response to injury, Altered Protein ...

Altered Protein Metabolism - Metabolic Response to Injury? Urinary nitrogen loss is extensive following injury, Trauma accelerates nitrogen turnover. In unfed patients, tissue

Define some advantages of breast milk for infants, Define some Advantages o...

Define some Advantages of breast milk for Infants? 1) Breast milk is a simple and natural method of feeding. It is hygienic, inexpensive and available at all times at the righ

What is the difference between vital and natural amino acid, Q. What is the...

Q. What is the difference between vital and natural amino acids? Essential amino acids are those that the organism is not capable to synthesize and that need to be ingested by

Define nutritional management of eating disorders, Define Nutritional Manag...

Define Nutritional Management of Eating Disorders? In the last unit, we focused on weight management. It is important to understand that the problems associated with too much d

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd