recap

6.2 recap

In multicellular organisms, cells arrange themselves into tissues via the processes of cell recognition and cell adhesion. These processes are mediated by membrane-associated proteins and carbohydrates. Cell membrane proteins also interact with the extracellular matrix. Cell junctions assist in strengthening tissues and allow cells to communicate with one another.

learning outcomes

You should be able to:

  • Design investigations to analyze the function of proteins and carbohydrates in cell adhesion and cell recognition.

  • Compare and contrast the three types of cell junctions found in animals.

Question 1

Describe an experiment showing a role for carbohydrates in cell recognition and adhesion.

Enzymes called glycosidases cut the bonds between carbohydrates and other molecules. Obtain cells that are bound together (e.g., sponges) and then separate them. Then treat the cells with glycosidases to remove carbohydrates. This should block cell recognition and adhesion.

Question 2

To which of the three types of cell junctions are plasmodesmata most similar (see Figure 5.7B)?

Plasmodesmata are most similar to gap junctions, because both have a membrane-lined channel.

You have seen how the cell membrane and molecules associated with it facilitate binding between cells and the maintenance of cell adhesion. We’ll turn now to another major function of membranes: regulating the substances that enter or leave a cell or organelle.