Types of cell wall, Biology

Assignment Help:

TYPES OF CELL WALL

Cell wall differentiated into the following layers :

1. Primary Cell Wall       2. Secondary Cell wall             3. Tertiary Cell wall

1.       PRIMARY CELL WALL (10 CELL WALL)

  • The first formed cell wall is known as primary cell wall, laid inner to the middle lamella.
  • The primary cell was is comparatively thin and permeable.
  • It consists of hemicellulose 50%, cellulose 20%, lipid 20%, Protein 1-2%, water 60%
  • Macrofibrils of cellulose are randomly distributed.
  • Found in all types of plant cell (meristematic & soft parenchymatous tissues like mesophyll, cortex, pith, fruit)
  • Microfibril are loose wavy & short. Lignin, Pectin is also present.
  • The primary cell wall of the yeast & the fungi is composed of the chitin.

2.       SECONDARY CELL WALL (20 CELL WALL)

  • The secondary cell wall is thick, permeable & lies near the plasma membrane or the tertiary cell wall.
  • It is composed of 3 layers S1, S& S3 (S2= thickest and S3 thinnest layer)
  • Chemically the secondary cell wall is composed of compactely arrange macrofibrils of the cellulose, hemicellulose, pectin & lignin. Hemicellulose 25%, cellulose 20-40%, Lipid - protein = negligible amount, Hydration = 30%
  • Formed by apposition / accretion (growth occur due to accretion) intussusception
  • To have a uniform thickness Intussusception method is better than apposition.
  • Thickness 3-10 mm, uniform thickness absent.
  • At places the thickning is absent it form pits.
  • It collenchyma it provides elasticity & allow for limited growth.
  • Macrofibrils arranged in a regular pattern (parallel to long axis)
  • Present in Sclerenchyma, Vessels, Tracheids. Absent in Meristem.
  • Thickening is of purely cellulose in collenchyma cells, cotton fibres, flax fibres.

3.       TERTIARY CELL WALL

  • In certain plant cells another cell wall found beneath the secondary cell wall which is known as tertiary cell wall.
  • It consists of xylan and hemicellulose. (Xylan is the polymer of xylulose.)
  • Tertiary cell wall found in tracheids of gymnosperms (Tension wood).

1005_cell wall.png


Related Discussions:- Types of cell wall

Nerve fibres, NERV E FIBRES - Axon or dendrite of a nerve cell cove...

NERV E FIBRES - Axon or dendrite of a nerve cell covered with one, two or three sheaths is called nerve fibre. Dendrites are surrounded only by one sheath. An axon may b

How do calcium ions participate in muscle contraction, Q. How do calcium io...

Q. How do calcium ions participate in muscle contraction? Why do both muscle relaxation and muscle contraction spend energy? In the muscle cells calcium ions are stored within

Define about the polyphenols, Define about the Polyphenols? We now come...

Define about the Polyphenols? We now come to a group of compounds, which were until recently considered to adversely influence nutrient absorption or giving colour to foods e.g

Illustrate the term cilia, Illustrate the term Cilia? A cellular hairli...

Illustrate the term Cilia? A cellular hairlike locomotory structure which comprises an extension of the plasma membrane surrounding a 9+2 organization of microtubules. Unlike f

Periods of cultural evouition and modern man, PERIOD S OF CULTURAL EVOUITI...

PERIOD S OF CULTURAL EVOUITION AND MODERN MAN - Paleolithic period: Stone age. Age of tools of stones and bones, cave paintings. Mesolithi c period: Age of domesticati

How enzyme to cut two pieces of dna, Critical Thinking Why is it necessary ...

Critical Thinking Why is it necessary to use the same restriction enzyme to cut two pieces of DNA that are to be joined together? As each restriction enzyme recognizes a specif

Illustrate omega taxonomy, Q. Illustrate Omega Taxonomy? After synthesi...

Q. Illustrate Omega Taxonomy? After synthesising a basic classification, the taxonomist can attempt to improve upon it. Therefore, the observed facts are interpreted in Omega t

Human evolution, In the last unit we traced the human evolutionary history ...

In the last unit we traced the human evolutionary history mostly from a palaeontological viewpoint. Although still fragmentary, the available fossil evidence makes it possible to c

Microbiology, harmful and benificial microbes

harmful and benificial microbes

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