Extracellular structures are produced by cells and secreted outside the cell membrane. Most consist of a fibrous component in a gel-
learning outcomes
You should be able to:
Explain structure–
Compare and contrast plant and animal cell extracellular matrices.
Analyze changes to cells involving extracellular components.
When a cancer spreads from the initial site to another location in the body, initial events are the detachment of the cancer cells from its surrounding extra cellular matrix and digestion of the matrix as the cell migrates. How might these events occur?
Initially, there is a digestion of molecules that attach the cell membrane to the extracellular matrix. Then enzymes are produced and secreted from the cell that digests the macromolecules of the extracellular matrix. The cell migrates by microfilaments.
How does the structure of a cell wall contribute to its function?
A cell wall contains cellulose fibers which provide strong support yet allow a plant to have some flexibility to bend. The cell wall structure provides an extra barrier that helps protect the cell from infection, yet cell walls in some cells have pores that allow the flow of materials in and out of the cell.
How could a biologist use chemical analysis to differentiate between a plant cell and an animal cell?
Chemical analysis could identify a plant cell by the presence of cellulose in the extracellular matrix and an animal cell by the presence of collagen in the extracellular matrix. These two compounds are distinct to the two different types of cells.
We have now discussed the structures and some functions of prokaryotic and eukaryotic cells. Both exemplify the cell theory, showing that cells are the basic units of life and of biological continuity. Much of the rest of this part of the book will deal with these two aspects of cells. There is abundant evidence that the simpler prokaryotic cells are more ancient than eukaryotic cells, and that the first cells were probably prokaryotic. We will now turn to the next step in cellular evolution, the origin of eukaryotic cells.