Signalling
Signalling allows cells to coordinate with the organism. It is the affect of signal
proteins + receptor proteins.
Signalling Distance is the distance between the signalling cell and the target cell.
Competence is the ability of a cell or tissue to respond to a signal.
The number of signalling proteins encoded by an organisms genome gives a
measure of its cell signalling capacity. Signalling capacity is quantified by
counting signalling genes. This means that researchers examine the genomes
of organisms and count the number of genes involved in producing signalling
molecules: receptors, ligands, enzymes, and transcription factors.
More complex multicellular organisms have a greater number of signalling
proteins, total number of proteins, and total % of signalling proteins.
The nature of signals can take many forms: proteins, small hydrophobic
molecules, small hydrophilic molecules, gas, electrical, they all transfer the
property of transferring information between cells.
Long Range Signalling shows competence. Signals is usually transmitted via
blood or sap. Many more cells are exposed to the signal than respond to it.
Signalling operates over different ranges so they can be categorised based on
their signalling range.
Signalling 1
, Endocrine Long Signalling Range - 1000mm (usually involving the endocrine
system).
Paracrine Intermediate Signalling Range - 1mm (paracrine system).
Juxtacrine Short Signalling Range - 0mm (juxtacrine signalling also known as
contact-dependent signalling where cells need to be in close contact).
Long Range Signalling
Male and Female Hormones in Sexual Dimorphism
In mammals differences in appearance between the sexes are driven by long
range signalling circuits.
The gonads secrete male or female hormones.
These are sensed by cells in the body.
This triggers the development of male or female appearance.
Flowering in Plants Triggered by Day Length
Long range signalling enables some plants to time their flowering according to
day length.
This allows plants of the same species to synchronise their flowering.
This is important for cross pollination.
A flower that comes out by itself will not get pollinated by another flower.
The sensor for sunlight is CO protein found in the leaf. CO is a plant protein which
regulates gene expression. CO protein levels in the leaf are sensitive to daylight.
CO protein accumulates when the days are long.
1. High CO Protein levels promote synthesis of FT protein.
2. FT protein levels are high in the leaf when the day is long.
3. FT protein moves through sap from leaf to the shoot.
4. The flower forms at the shoot.
In plants only the shoot (not the leaf) is competent to responding to the FT protein
by flowering. Other cells/tissues cannot respond so they are incompetent.
Signalling 2
Signalling allows cells to coordinate with the organism. It is the affect of signal
proteins + receptor proteins.
Signalling Distance is the distance between the signalling cell and the target cell.
Competence is the ability of a cell or tissue to respond to a signal.
The number of signalling proteins encoded by an organisms genome gives a
measure of its cell signalling capacity. Signalling capacity is quantified by
counting signalling genes. This means that researchers examine the genomes
of organisms and count the number of genes involved in producing signalling
molecules: receptors, ligands, enzymes, and transcription factors.
More complex multicellular organisms have a greater number of signalling
proteins, total number of proteins, and total % of signalling proteins.
The nature of signals can take many forms: proteins, small hydrophobic
molecules, small hydrophilic molecules, gas, electrical, they all transfer the
property of transferring information between cells.
Long Range Signalling shows competence. Signals is usually transmitted via
blood or sap. Many more cells are exposed to the signal than respond to it.
Signalling operates over different ranges so they can be categorised based on
their signalling range.
Signalling 1
, Endocrine Long Signalling Range - 1000mm (usually involving the endocrine
system).
Paracrine Intermediate Signalling Range - 1mm (paracrine system).
Juxtacrine Short Signalling Range - 0mm (juxtacrine signalling also known as
contact-dependent signalling where cells need to be in close contact).
Long Range Signalling
Male and Female Hormones in Sexual Dimorphism
In mammals differences in appearance between the sexes are driven by long
range signalling circuits.
The gonads secrete male or female hormones.
These are sensed by cells in the body.
This triggers the development of male or female appearance.
Flowering in Plants Triggered by Day Length
Long range signalling enables some plants to time their flowering according to
day length.
This allows plants of the same species to synchronise their flowering.
This is important for cross pollination.
A flower that comes out by itself will not get pollinated by another flower.
The sensor for sunlight is CO protein found in the leaf. CO is a plant protein which
regulates gene expression. CO protein levels in the leaf are sensitive to daylight.
CO protein accumulates when the days are long.
1. High CO Protein levels promote synthesis of FT protein.
2. FT protein levels are high in the leaf when the day is long.
3. FT protein moves through sap from leaf to the shoot.
4. The flower forms at the shoot.
In plants only the shoot (not the leaf) is competent to responding to the FT protein
by flowering. Other cells/tissues cannot respond so they are incompetent.
Signalling 2
