The upcoming discussion will update you about the difference between cell communication and signal transduction.
Difference # Cells Communication:
All living cells communicate with each other through one or other form of signal. These signals may be environmental factors or may be produced by other cells.
Even in unicellular organisms like yeast chemical signals are released to stop proliferation and prepare for sexual reproduction. These are called peptide secreting factors (PSFs).
In multicellular organisms, cell-to-cell signalling may be divided into 4-categories:
1. Autocrine Signalling:
The signal molecules released by a cell act on the cell itself inducing it to respond.
2. Paracrine Signalling:
The signal molecule released by one cell acts locally on neighbouring cells.
3. Endocrine Signalling:
The signals are released by an endocrine gland in the form of hormones, which are carried to other cells by the blood and finally perceived by the target cells.
4. Synaptic Signalling:
In the organisms like mammals and other complex multicellular organisms short range signalling is not sufficient. For these organisms specialized cells have evolved, which are called neurons. These cells are involved in signalling between the two parts of bodies. Neurons receive, conduct and transmit signals at their junctions called synapse.
In all these instances, it is necessary for the target cell to have specific target molecules which recognise and find signal molecule. This binding initiates a series of events ultimately causing the cell to respond in the desired manner.
In a cell, the signal molecule may produce the following effects:
1. It may cause an immediate change in the metabolism of the cell.
2. It may bring about immediate change in the electrical potential across the cell membrane.
3. It may influence the process of gene expression.
Difference # Signal Transduction:
Transmission of impulse or transduction of signal to the target cell may be done directly or indirectly.
1. Direct Signal Transduction:
In this type of transduction, the signal molecules are directly transmitted to the nucleus, where they bind with specific segments of the genes and influence their transcription.
2. Indirect Signal Transduction:
In this process, the signal molecule (also called ligand in this case) does not enter the cell directly. Instead, it binds with a receptor molecule located at the cell-surface of the target cell. Cell-surface receptors are trans-membrane proteins that span across the plasma membrane.
Formation of ligand-receptor complex brings about a change in the conformation of receptor molecule. This change is transmitted in the cytoplasm where it generates a series of intracellular signals which are transmitted to genes in the nucleus. This pathway involving the operation of different proteins between cell membrane and nucleus is called signal transduction pathway.