Intercellular Channels: Gap Junctions and Plasmodesmata

Flashcards covering the structure, function, and differences between gap junctions in animal cells and plasmodesmata in plant cells, based on lecture notes on intercellular channels.

What are intercellular channels and what do they allow?

Intercellular channels are structures that allow the direct movement of substances between adjacent cells in multicellular organisms.

What are gap junctions?

Gap junctions are a type of intercellular junction found between animal cells, characterized by a small gap between their plasma membranes, which facilitate direct cell-to-cell communication.

Where are gap junctions abundant?

Gap junctions are abundant in tissues and organs where cells need to communicate extensively, such as in cardiac muscle cells, to enable coordinated contraction.

What specific molecules can pass through gap junctions?

Gap junctions allow the passage of ions and small molecules, including amino acids, sugars, and signaling molecules such as Ca2+ and cAMP, but not RNA, proteins, or polysaccharides.

What are connexins and connexons?

Connexins are integral membrane proteins that form gap junctions in vertebrates. Six connexin proteins form a channel called a connexon, and two aligned connexons form an intercellular channel.

What are plasmodesmata?

Plasmodesmata are intercellular channels found between adjacent plant cells, connecting their cytosols and allowing direct movement of substances.

How do plasmodesmata differ structurally from gap junctions?

Unlike gap junctions, plasmodesmata feature a continuous plasma membrane between adjacent cells and also contain a central tubule, called a desmotubule, which connects the smooth ER membranes of adjacent cells.

What types of molecules can pass through plasmodesmata?

In their open state, plasmodesmata allow passage of ions and small molecules (e.g., sugars, ATP). When dilated, they can allow passage of macromolecules (e.g., proteins, mRNA) and even viruses.

What is the function of plasmodesmata in different states?

In the open state, plasmodesmata allow passage of ions and small molecules. They tend to close when a plant is wounded to prevent loss of water and nutrients, and can dilate to allow passage of macromolecules and viruses.

Who first observed intercellular connections in plant cells and when?

Eduard Tangl, a Russian botanist, first observed intercellular connections (now known as plasmodesmata) in the seeds of the strychnine tree in 1879.