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This illustration shows two plant cells side-by-side. A gap in the cell wall, a plasmodesma, allows fluid and small molecules to pass from the cytoplasm of one cell to the cytoplasm of the other.
A plasmodesma is a channel between the cell walls of two adjacent plant cells. Plasmodesmata allow materials to pass from the cytoplasm of one plant cell to the cytoplasm of an adjacent cell.

Tight junctions

A tight junction    is a watertight seal between two adjacent animal cells ( [link] ). The cells are held tightly against each other by proteins (predominantly two proteins called claudins and occludins).

This illustration shows two cell membranes joined together by a matrix of tight junctions.
Tight junctions form watertight connections between adjacent animal cells. Proteins create tight junction adherence. (credit: modification of work by Mariana Ruiz Villareal)

This tight adherence prevents materials from leaking between the cells; tight junctions are typically found in epithelial tissues that line internal organs and cavities, and comprise most of the skin. For example, the tight junctions of the epithelial cells lining your urinary bladder prevent urine from leaking out into the extracellular space.

Desmosomes

Also found only in animal cells are desmosomes , which act like spot welds between adjacent epithelial cells ( [link] ). Short proteins called cadherins in the plasma membrane connect to intermediate filaments to create desmosomes. The cadherins join two adjacent cells together and maintain the cells in a sheet-like formation in organs and tissues that stretch, like the skin, heart, and muscles.

This illustration shows two cells fused together by a desmosome. Cadherins extend from each cell and join the two cells together. Intermediate filaments connect to cadherins on the inside of the cell.
A desmosome forms a very strong spot weld between cells. It is created by the linkage of cadherins and intermediate filaments. (credit: modification of work by Mariana Ruiz Villareal)

Gap junctions

Gap junctions in animal cells are like plasmodesmata in plant cells in that they are channels between adjacent cells that allow for the transport of ions, nutrients, and other substances that enable cells to communicate ( [link] ). Structurally, however, gap junctions and plasmodesmata differ.

This illustration shows two cells joined together with protein pores called gap junctions that allow water and small molecules to pass through.
A gap junction is a protein-lined pore that allows water and small molecules to pass between adjacent animal cells. (credit: modification of work by Mariana Ruiz Villareal)

Gap junctions develop when a set of six proteins (called connexins) in the plasma membrane arrange themselves in an elongated donut-like configuration called a connexon. When the pores (“doughnut holes”) of connexons in adjacent animal cells align, a channel between the two cells forms. Gap junctions are particularly important in cardiac muscle: The electrical signal for the muscle to contract is passed efficiently through gap junctions, allowing the heart muscle cells to contract in tandem.

To conduct a virtual microscopy lab and review the parts of a cell, work through the steps of this interactive assignment .

Section summary

Animal cells communicate via their extracellular matrices and are connected to each other via tight junctions, desmosomes, and gap junctions. Plant cells are connected and communicate with each other via plasmodesmata.

When protein receptors on the surface of the plasma membrane of an animal cell bind to a substance in the extracellular matrix, a chain of reactions begins that changes activities taking place within the cell. Plasmodesmata are channels between adjacent plant cells, while gap junctions are channels between adjacent animal cells. However, their structures are quite different. A tight junction is a watertight seal between two adjacent cells, while a desmosome acts like a spot weld.

Questions & Answers

what is the protein found in the blood?
Tobias Reply
globin
Joelia
Globin
what is parasitic movement
Emmanuel Reply
Parasitic movement is a problem for all of us. So is its companion, parasitic tension. Parasitic movement is the excess contraction of muscles that you don't actually need to complete an action.
freya
what are eukaryotic cells
Thiza Reply
what is the mean of pair of chromosomes
Kazula Reply
hi
Lagos
23 haploid and 23diploid
Patson
how are you studying in this quarantine? .. how are you keeping yourselves motivated?
sivajijadhav @815.com
good morning guyz
Joelia
morning
Kazula
hi
Justin
Good
Angela
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Angela
what is the important of sex
Aremu Reply
why did human being need sex?
Aremu
because he/she have feelings
Chripine
reproduction...to make more
Yazi
due to active harmon
Manish
One important of sex is to reproduce
Emma
to ensure the countinuty of life
Yusuf
all of you are right
Edith
what is momentum
Asiya Reply
The strength or force that allows something to continue or grow stronger or faster as time pass
Emma
What is Centripetal Force?
Justin
centrepital force is the inward force required to keep a body moving with constant speed in a circular path
Yusuf
what is the test for protein
Takii Reply
List four condition necessary for seed germination
Tedeka Reply
water,air(oxygen),light,temperature
Hassan
water, light, oxygen and temperature
lilchris
water, oxygen, light temperature
Mike
water oxygen light and temperature
John
importance of biology
Alabina Reply
importance of boilogy
Alabina
what is soil
Amina Reply
soil is the upper part of the earth
Alabina
what is importance of studying biology
Alabina
soil is the uppermost layer of the earth on which plant grows
Yusuf
soil is defined as the thin surface of the upper most layer of the earth crust on which plants grow
Thanni
soil is the upper part of the earth which plants grow on
Emma
differences between euglenoid and amoeboid
Grace Reply
what are the difference between aerobic and anaerobic respiration?
Maxwell Reply
Aerobic respiration involves the use of oxygen whiles anaerobic respiration does not involve the use of oxygen
Quabena
what is assmilation
Lucy Reply
what is cell
Manish Reply
cell is the structural and functional unit of life or living things
hamid
where anaerobic respiration occurre?
Manish
in cell
Manish
in cells?
Manish
where anaerobic respiration occurre in cell?
Manish

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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