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

Gregor mendel, why green seeds reappeared in the f2 generation

why green seeds reappeared in the f2 generation

How to measure blood pressure, Q. How to measure Blood Pressure? With t...

Q. How to measure Blood Pressure? With the onset of exercise, the resistance to blood flow through contracting muscles decreases significantly and results in a fall in the peri

Define methods for studying the nutrient requirements, Define Methods for S...

Define Methods for Studying the Nutrient Requirements? 1) Population survey of nutrient intakes of healthy individuals is one method of estimating nutrient requirements. The av

Explain biotin (vitamin h), Biotin (vitamin H) It was revealed  that eg...

Biotin (vitamin H) It was revealed  that egg yolk could prevent dermatitis and emaciation  in  rats that were kept on  raw  egg white a$ the main protein source. The factor of

Initiation of development - development biology, Initiation of Development ...

Initiation of Development - Development Biology We know that the various events collectively called the activation programme. These events are directly related to the formatio

Factors affecting biotic potential - population growth, Factors Affecting B...

Factors Affecting Biotic Potential - Population Growth Biotic potential differs from one species to another e.g., bacterial populations can grow faster than population of oak

Calcium requirements of school children and adolescents, Determine Calcium ...

Determine Calcium requirements of school children and adolescents? Calcium requirements in children and adolescents can be calculated on the basis of Calcium accretion during g

Striped muscles, STRIPED MUSCLES - These muscles are found in the li...

STRIPED MUSCLES - These muscles are found in the limbs, body walls, tongue, pharynx and beginning of oesophagus and are under the control of animal's will. These muscle f

Hemodynamic measurements of tricuspid stenosis, Q. Hemodynamic Measurements...

Q. Hemodynamic Measurements of tricuspid stenosis? Unless one suspects it clinically and echocardiographically, and plans the hemodynamic study - diagnosis of tricuspid stenosi

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