Cell surface junctions, Biology

CELL SURFACE JUNCTIONS

(1)      Desmosomes (Maculae adherence) - Thickened circular areas on P.M. of adjacent cells with radiating fibrils in cytoplasm. These fibrils called tonofibrils. Desmosomes generally occurs in epithelial cells and provide cell adhesion. Desmosomes without tonofibrils are called terminal bars.

(2)      Tight junction or Zona occludence - outer most layers of two P.M. at the site of attachment fuse completely.

Fused membrane reveals a 5- layered structure. Permeability of ions is more at tight junction. Tight junction occurs in nerve tissue at synapses. (electrical synapse)

(3)      Gap junction or Nexus - Fine protein channel (connexon) join two P.M of adjacent cells. Exchange of ions between cells may takes place by protein channels. Desmosomes, Tight junction and Gap junction occurs in animal cell.

(4)      Plasmodesmata - Name proposed by strassburger. Cytoplasmic connection bet. Two adjacent cells through pores in cell wall and cell membrane. Plasmodesmata are characteristic of multi-cellular plants and they maintain continuity of cytoplasm between adjacent cells. Plasmodesmata often contain an expanded E.R. termed as desmotubule.

1124_modifications of cell membrane.png

Posted Date: 10/5/2012 6:31:36 AM | Location : United States







Related Discussions:- Cell surface junctions, Assignment Help, Ask Question on Cell surface junctions, Get Answer, Expert's Help, Cell surface junctions Discussions

Write discussion on Cell surface junctions
Your posts are moderated
Related Questions
Contraceptive methods The safe and easy methods to prevent pregnancy are called contraceptive methods. i) Contraceptive methods followed by females are : 1) Use of harmon

Explain some Characteristic Features of Mucor? 1. Stolons characteristics of Rhizopus are absent in Mucor. The aerial mycelium in Mucor consists of branched hyphae, which grow

Proteins Proteins are continually synthesised in the cells as they are the principal component required for growth. Proteins are composed of amino acids which are derived larg

Define Classification of Lipids? Chemically, lipids are the organic molecules poor in oxygen content, soluble in organic solvents but insoluble in water. They are classified as

Small-  and  medium-chain   acyl  CoA  molecules  (up  to  10  carbon  atoms)  are readily capable to cross the inner mitochondrial  membrane by diffusion. Furthermore, longer chai

Q. What are the etiological agents of malaria? The etiological agents of malaria are protozoans of the genus Plasmodium. There are four different kinds of plasmodia that cause

Q. Show the Collection of Primary Samples of grain? Sampling of grains begins with the collection of the primary sample i.e. sample of the consignment. The process involved in

P ANCREAS It is an elongated, leaf like, yellowish or orangish in colour. Lying partly behind stomach. 16 cm long, 2.5 cm. wide & weight about 60 gms. It consists of hea

Which one of the following is not a lateral meristem? 1. Intrafascicular cambium 2. Interfascicular cambium 3. Phellogen 4. Intercalary meristem   Intercalary m

Q. What are the ions? What are the two kinds of molecules into which ions are classified ? Ions are substances or atoms electrically charged by means of gain or loss of electron