Junctions Flashcards
Desmosomes structure & function
Localised patches that hold two cells tightly together, but have small gaps to allow flow of materials. They form links between cells by connecting intermediate filaments of cytoskeleton and are further linked by cadherins. The junctions are lined along the cell membrane in areas known as plaques, and they give strength & stability to cells subjective to stress.
Tight junctions structure & function
Act as a ‘sealing’ junction and form leak-proof seals between cells so that material has to enter through transport mechanisms provided by transmembrane proteins. The membrane proteins are arranged like beads on string that span the membranes of each junction.
Gap junction structure & function
Specialised areas of the cell membrane connecting the cytoplasm of adjacent cells. They are made up of 4 transmembrane proteins called connexins & 6 connexins make up a connexon channel. When two connexons “dock” together, a gap junction is formed. Gap junctions allow passage of ions and other small molecules such as amino acids & sugars.
Plasmodesmata structure & function
Allows exchange of small molecules such as sugars & amino acids between the cytoplasm of cells. This is called cytoplasmic streaming. The streaming of molecules can be regulated by constricting or dilating the openings at each end of the channel. They are cylinder-like bridges connecting one cell with another, linking the cell walls & is lined by plasma membrane, meaning the cytoplasm of neighbouring cells are linked.
