Chapter 11: Cell Communication
Cells can signal to each other and interpret signals they receive from other cells and the environment.
-These signals can include touch and light, but are most often chemicals.
11.1: External signals are converted to responses within the cell
Evolution of Cell Signaling
The yeast Saccharomyces cerevisiae identify their mates by chemical-signaling
-their are two "sexes, " one called a and one called α
-these mating types secrete different mating factors that only bind
to the receptors of the opposite type
- a factors bind receptors on α cells, and α factors bind receptors on a cells
- When exposed to the others mating factor, the a and α cells will grow toward one another
until they fuse, producing a new a/α cell that contains the hereditary information of both parent cells
Cell-signaling, like most other cellular processes, support the evolutionary relatedness of all cells.
-the same set of cell-signaling mechanisms are present throughout many diverse species (such as yeast and animals).
-this suggests that early versions of cell-signaling evolved well before the first multicellular organism arose.
-Scientists believe that these signaling mechanisms developed in ancient prokaryotes and single celled eukaryotes, prior to being adopted by their multicellular descendants
Bacterial cells secrete molecules that can be detected by other bacterial cells
-Quorum sensing: the ability of bacteria cells to sense the concentration of signaling molecules, allowing them to monitor
the local density of cells.
- this allows bacterial cells to work together to achieve tasks that require a particular number of cells
-Biofilm: a group of bacterial cells adhered to a surface, from which they are gaining nutrition.
-slimy coating on a log in the woods, slime on your teeth when you wake up
Local and Long-Distance Signaling
Cells in a multicellular organism communicate using signaling molecules that are specific to their target cells
-They may target cells that are local or even adjacent to them, or cells that are further away.
Local Signaling:
1) Cell Junctions: both plant and animal cells have junctions between cells that connect the cytoplasm of adjacent cells, allowing signaling substances in the cytoplasm to flow freely between the cells.
-Animals: Gap junctions
-Plants: Plasmodesmata
2) Cell to cell Recognition: cells in animals may recognize nearby cells by the molecules protruding from their surfaces (glycoproteins or glycolipids)
3) Messenger Molecules: molecules secreted by the signaling molecule, travel to receiving cell with complementary receptors.
-Paracrine signaling: when the signal is produced and received locally
-An example of locally acting messenger molecules in animal cells are growth factors.
-Growth factors can stimulate multiple cells simultaneously in the nearby area to grow and divide.
-Synaptic signaling: specialized type of local cell-signaling occurs between neurons, and is called.
-synapse: small space between a nerve cell and its target cell
-a nerve cell releases neurotransmitters into a synapse , stimulating the target cell, such as a muscle or nerve cell.
Long-Distance Signaling:
1) Hormones: chemicals released from specialized cells that travel via the circulatory system to their targets.
-Endocrine signaling: hormonal signaling
- plant hormones sometimes travel in vessels, however, most hormones travel by moving through cells or by diffusing through the air as a gas
Signaling molecules, both local and long distance, vary in size and function.
-The ability of a cell to respond to a signaling molecule is dependent on whether or not it has the appropriate receptor
The Three Stages of Cell Signaling: A Preview
Earl W. Sutherland:
-research using epinephrine (responsible for the fight or flight response)
-found that epinephrine does not interact directly with the enzyme responsible for glycogen breakdown, so there must be some
step/s between the signal and the reaction.
- Also found that the cell membrane was required for the signal's transmission
Three Stages of Cell Signaling:
1) Reception
Cells can signal to each other and interpret signals they receive from other cells and the environment.
-These signals can include touch and light, but are most often chemicals.
11.1: External signals are converted to responses within the cell
Evolution of Cell Signaling
The yeast Saccharomyces cerevisiae identify their mates by chemical-signaling
-their are two "sexes, " one called a and one called α
-these mating types secrete different mating factors that only bind
to the receptors of the opposite type
- a factors bind receptors on α cells, and α factors bind receptors on a cells
- When exposed to the others mating factor, the a and α cells will grow toward one another
until they fuse, producing a new a/α cell that contains the hereditary information of both parent cells
Cell-signaling, like most other cellular processes, support the evolutionary relatedness of all cells.
-the same set of cell-signaling mechanisms are present throughout many diverse species (such as yeast and animals).
-this suggests that early versions of cell-signaling evolved well before the first multicellular organism arose.
-Scientists believe that these signaling mechanisms developed in ancient prokaryotes and single celled eukaryotes, prior to being adopted by their multicellular descendants
Bacterial cells secrete molecules that can be detected by other bacterial cells
-Quorum sensing: the ability of bacteria cells to sense the concentration of signaling molecules, allowing them to monitor
the local density of cells.
- this allows bacterial cells to work together to achieve tasks that require a particular number of cells
-Biofilm: a group of bacterial cells adhered to a surface, from which they are gaining nutrition.
-slimy coating on a log in the woods, slime on your teeth when you wake up
Local and Long-Distance Signaling
Cells in a multicellular organism communicate using signaling molecules that are specific to their target cells
-They may target cells that are local or even adjacent to them, or cells that are further away.
Local Signaling:
1) Cell Junctions: both plant and animal cells have junctions between cells that connect the cytoplasm of adjacent cells, allowing signaling substances in the cytoplasm to flow freely between the cells.
-Animals: Gap junctions
-Plants: Plasmodesmata
2) Cell to cell Recognition: cells in animals may recognize nearby cells by the molecules protruding from their surfaces (glycoproteins or glycolipids)
3) Messenger Molecules: molecules secreted by the signaling molecule, travel to receiving cell with complementary receptors.
-Paracrine signaling: when the signal is produced and received locally
-An example of locally acting messenger molecules in animal cells are growth factors.
-Growth factors can stimulate multiple cells simultaneously in the nearby area to grow and divide.
-Synaptic signaling: specialized type of local cell-signaling occurs between neurons, and is called.
-synapse: small space between a nerve cell and its target cell
-a nerve cell releases neurotransmitters into a synapse , stimulating the target cell, such as a muscle or nerve cell.
Long-Distance Signaling:
1) Hormones: chemicals released from specialized cells that travel via the circulatory system to their targets.
-Endocrine signaling: hormonal signaling
- plant hormones sometimes travel in vessels, however, most hormones travel by moving through cells or by diffusing through the air as a gas
Signaling molecules, both local and long distance, vary in size and function.
-The ability of a cell to respond to a signaling molecule is dependent on whether or not it has the appropriate receptor
The Three Stages of Cell Signaling: A Preview
Earl W. Sutherland:
-research using epinephrine (responsible for the fight or flight response)
-found that epinephrine does not interact directly with the enzyme responsible for glycogen breakdown, so there must be some
step/s between the signal and the reaction.
- Also found that the cell membrane was required for the signal's transmission
Three Stages of Cell Signaling:
1) Reception