Chapter 11: Cell-Cell Interactions

11.1 The Cell Surface

Virtually all plant cells are surrounded by a cell wall-a fiber composite that is the basis of major industries.
When plant cells first form, they secrete an initial fiber composite called a primary cell wall.
The fibrous component of the primary cell wall consists of long strands of the polysaccharide cellulose. These strands are bundled into stout structures termed microfibrils.
The spaces between microfibrils are filled with gelatinous polysaccharides such as pectins-the molecules that are used to thicken jams and jellies.
The force exerted by the cell against the wall is known as turgor pressure.
Expansins disrupt the hydrogen bonds that crosslink microfibrils to other polymers in the wall, loosening the structure and allowing the microfibrils to slide past one another.
As plant cells mature and stop growing, they may secrete an additional layer of material-a secondary cell wall-between the plasma membrane and the primary cell wall.
In cells that form wood, the secondary cell wall also contains lignin, a complex polymer that forms an exceptionally rigid network.
Most animal cells secrete a fiber composite called the extracellular matrix, or simply ECM.
The fibrous component of animal ECM is dominated by glycoproteins named collagen
The ground substance that surrounds collagen and other fibrous components of the ECM contains highly glycosylated, gel forming proteins called proteoglycans
A tissue consists of similar cells that function as a unit.
Membrane proteins called integrins bind to extracellular cross-linking proteins, including laminins, which in turn bind to other components of the ECM.

11.2 How Do Adjacent Cells Connect and Communicate?

Direct physical connections between cells are the basis of multicellularity.
Materials and structures that bind cells together are particularly important in epithelial-tissues that form external and internal surfaces.
A tight junction is a cell-cell attachment composed of specialized proteins in the plasma membranes of adjacent animal cells
Desmosome is a strong cell-cell attachment particularly common in animal epithelial cells and certain muscle cells.
As the experiment continued, cells began to aggregate based on their origin-adhering to other cells of the same tissue type. This phenomenon is now called selective adhesion.
An antibody is a protein produced by an immune response that binds specifically to a unique type of molecule, often another protein
Cadherins are the linking proteins in desmosomes
In many animal tissues, structures called gap junctions connect adjacent cells.
In plants, gaps through cell walls allow direct connections between the cytoplasm of adjacent cells which are called plasmodesmata
Symplast is a continuous network of cytoplasm connected by plasmodesmata.
Apoplast is the region outside the plasma membrane

11.3 How Do Distant Cells Communicate?

Hormones are information-carrying molecules that are secreted by plant and animal cells into bodily fluids and act on distant target cells.
A signal receptor is a protein that changes its shape and activity after binding to a signaling molecule.
Important information regarding signal receptors include:
- Receptors are dynamic
- Receptors can be blocked
Signal transduction is the conversion of a signal from one form to another.
Many signal receptors span the plasma membrane and are closely associated with peripheral membrane proteins inside the cell called G proteins.
Second messenger is a small, nonprotein signaling molecule or ion that elicits an intracellular response to the first messenger
Protein kinases are enzymes that activate or inactivate other proteins by adding a phosphate group to them.
This sequence of protein modifications that culminates in a cell response is termed a phosphorylation cascade.

11.4 Signaling between Unicellular Organisms

The use of signaling pathways to respond to population density in prokaryotic and eukaryotic microbes is referred to as quorum sensing.
Cell signaling helps organisms ranging from bacteria to blue whales receive information about their environment and respond appropriately to changing conditions.

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Chapter 11: Cell-Cell Interactions

11.1 The Cell Surface

Virtually all plant cells are surrounded by a cell wall-a fiber composite that is the basis of major industries.
When plant cells first form, they secrete an initial fiber composite called a primary cell wall.
The fibrous component of the primary cell wall consists of long strands of the polysaccharide cellulose. These strands are bundled into stout structures termed microfibrils.
The spaces between microfibrils are filled with gelatinous polysaccharides such as pectins-the molecules that are used to thicken jams and jellies.
The force exerted by the cell against the wall is known as turgor pressure.
Expansins disrupt the hydrogen bonds that crosslink microfibrils to other polymers in the wall, loosening the structure and allowing the microfibrils to slide past one another.
As plant cells mature and stop growing, they may secrete an additional layer of material-a secondary cell wall-between the plasma membrane and the primary cell wall.
In cells that form wood, the secondary cell wall also contains lignin, a complex polymer that forms an exceptionally rigid network.
Most animal cells secrete a fiber composite called the extracellular matrix, or simply ECM.
The fibrous component of animal ECM is dominated by glycoproteins named collagen
The ground substance that surrounds collagen and other fibrous components of the ECM contains highly glycosylated, gel forming proteins called proteoglycans
A tissue consists of similar cells that function as a unit.
Membrane proteins called integrins bind to extracellular cross-linking proteins, including laminins, which in turn bind to other components of the ECM.

11.2 How Do Adjacent Cells Connect and Communicate?

Direct physical connections between cells are the basis of multicellularity.
Materials and structures that bind cells together are particularly important in epithelial-tissues that form external and internal surfaces.
A tight junction is a cell-cell attachment composed of specialized proteins in the plasma membranes of adjacent animal cells
Desmosome is a strong cell-cell attachment particularly common in animal epithelial cells and certain muscle cells.
As the experiment continued, cells began to aggregate based on their origin-adhering to other cells of the same tissue type. This phenomenon is now called selective adhesion.
An antibody is a protein produced by an immune response that binds specifically to a unique type of molecule, often another protein
Cadherins are the linking proteins in desmosomes
In many animal tissues, structures called gap junctions connect adjacent cells.
In plants, gaps through cell walls allow direct connections between the cytoplasm of adjacent cells which are called plasmodesmata
Symplast is a continuous network of cytoplasm connected by plasmodesmata.
Apoplast is the region outside the plasma membrane

11.3 How Do Distant Cells Communicate?

Hormones are information-carrying molecules that are secreted by plant and animal cells into bodily fluids and act on distant target cells.
A signal receptor is a protein that changes its shape and activity after binding to a signaling molecule.
Important information regarding signal receptors include:
- Receptors are dynamic
- Receptors can be blocked
Signal transduction is the conversion of a signal from one form to another.
Many signal receptors span the plasma membrane and are closely associated with peripheral membrane proteins inside the cell called G proteins.
Second messenger is a small, nonprotein signaling molecule or ion that elicits an intracellular response to the first messenger
Protein kinases are enzymes that activate or inactivate other proteins by adding a phosphate group to them.
This sequence of protein modifications that culminates in a cell response is termed a phosphorylation cascade.

11.4 Signaling between Unicellular Organisms

The use of signaling pathways to respond to population density in prokaryotic and eukaryotic microbes is referred to as quorum sensing.
Cell signaling helps organisms ranging from bacteria to blue whales receive information about their environment and respond appropriately to changing conditions.