Question

Compare/contrast the various animal cell junctions to structures in plants and fungi.

Answer 1

Cells can communicate with each other through direct contact and are referred to as intercellular junctions. Cell junctions are a class of cell structures made up of multiprotein complexes that provide contact between cells and the extracellular matrix or cell-cell communication in animals. The extracellular matrix holds the cells together to form a tissue and also allows the cells within the tissue to communicate with each other. There are some differences in the ways that plant and animal cells do this. Animal cells consist of three major types of intercellular junctions such as
1) Adherens junctions, desmosomes, and hemidesmosomes (anchoring junctions)
2) Gap junctions (communicating junction)
3) Tight junctions (occluding junctions).
Thus in animal cells communication through extracellular matrices takes place using tight junctions, desmosomes, and gap junctions. A tight junction or occluding junction is a watertight seal between the neighboring animal cells. The cells are held tightly against each other by proteins (predominantly two proteins called claudins and occludins). This tight adherence prevents leakage of transported solutes and water and seals the paracellular pathway. Eg; epithelial tissue that lines internal organs and cavity, such as urinary bladder prevent urine from leaking out into the extracellular space. The desmosomes are seen only in animal cells and provide strong adhesion between adjacent epithelial cells. Cadherin (short proteins) in the plasma membrane connect to intermediate filaments to develop desmosomes. Gap junctions in animal cells permit the transport of ions, nutrients, and other substances that enable cells to communicate with adjacent cells. These Gap junctions in animal cells are like plasmodesmata in the mode of functioning but they differ in structures. Plasmodesmata are junctions between plant cells and help in cell-cell communication. Plant cells are surrounded by cell walls but they don’t contact each other through wide stretches of plasma membrane-like animal cells does. Therefore, a specialized junction called plasmodesmata in plant cells enables the transport and communication between them.
In fungi, similar communication channels are known as septal spores. The communication between the cells through septal pores ensures long‐range communication and exchange of cytoplasm, proteins, and organelles throughout the length of the hypha. Fungi also protect their cells from this catastrophic outcome by septal pore occlusion. This can be achieved by the deposition of proteinaceous material or by the movement of organelles into the septal pore.