Module 2/ Cell junctions

Question 1

Plasmodesmata

Answer 1

-Neighbouring cell of multicellular organisms adhere and communicate to one another.

-In plants, neighbouring cell are connected by cytoplasmic channels called plasmodesmata that go through the cell walls, making the membrane continuous between cells.

Question 2

Example of plasmodesmata

Answer 2

Short-root (Shr) proteins: transcription factor responsible for the outwards cell division in the root.

-Fluorescent DNA probe (DNA labelled with a fluorophore) shows that Shr messenger RNA (mRNA) is only found in central stele cells (Ste in A) where it is synthesized and transcripted into protein.

-Fluorescently labelled proteins indicated that the Shr protein is present in both stele cells (Ste) and endothelial cells (End in B) and is located in the nucleus.

-She proteins pass through plasmadoesmata and reach the neighbouring cell layers (outwards movement).

Question 3

3 types of cell junction

Answer 3

Tight junction, Desmosomes and gap junction

Question 4

Tight junction

Answer 4

Tight junction are the plasma membrane of adjacent cell that are bound together by proteins.

-The prevent leakage of fluid through the epithelium layers, its impermeable.

Question 5

Desmosomes

Answer 5

Desmosomes are anchors of adjacent cells together through transmembrane proteins (that belong to the cadherins family) that are linked to the intermediate filaments.

-They keep adjacent cells tight together, especially in tissue that can stretch.

Question 6

Gap junction

Answer 6

Gap junction are similar to plasmodesmata. They have 6 proteins (connexins) that form a channel and allow the communication of adjacent cells.

-Letting though ions and small molecules such as amino acis, sugars.

Ex: heart muscles cells