Sketch and label a tight junction, desmosome, and gap junction.

Sure, I can describe and label each of these cell junctions for you.

Tight junction: A tight junction is a type of junction between cells that forms a barrier to the passage of molecules and ions through the space between cells. It consists of integral membrane proteins such as claudins and occludins, which form strands that seal the space between adjacent cells. I will label this as "TJ" on the cell membrane.

Desmosome: A desmosome is a type of cell junction that anchors adjacent cells together, providing mechanical strength to tissues. It consists of cadherin proteins that link to intermediate filaments inside the cell. I will label this as "D" on the cell membrane.

Gap junction: A gap junction is a type of cell junction that allows for direct communication and passage of small molecules and ions between adjacent cells. It consists of connexin proteins that form channels between cells. I will label this as "GJ" on the cell membrane.

I hope this helps to visualize and understand these different types of cell junctions.