Question

What is cellular signal transduction? Explain the general principles and features of signal transduction.

Answer 1

Signal transduction also known as cell signalling, it is basically a transmission of molecular signals from a cell receptor (outside) to cell cytosol (inside). The signal transmitted by a cell should be effectively transmitted to another cell, this is taken care of by the cell surface receptors.

The cell-signalling transmission is continued either by a series of biochemical reactions and changes within the cells or by the change in the cell membrane potential by movements of ions.in or out of the cell.

The signal transduction receptors are of 4 major types:

1. Enzyme-linked receptors: These are the group of multi-subunit transmembrane receptor either intrinsic enzyme or is associated with the intracellular enzyme.
2. Transmembrane receptors: also known as a 7-TM receptor or G-protein coupled receptor are integral membrane proteins that contain 7 membrane-spanning helices.
3. Nuclear Receptor: Also known as Nuclear hormone receptor, are a large family of that binds directly to DNA to regulate the expression of target genes. They basically regulate the response to hormones such as steroids.
4. Ligan gated-ion receptor: They are a large group of intrinsic transmembrane protein that allows passage of ions upon activation by a specific chemical.

The general principle of Signal transduction:

Basically, an environmental signal such as a hormone or sex steroid or ion is first received by interaction with the cellular component (cell-surface receptor). The information that the signal is received by the receptor is then converted into other chemical forms, or what it is called as transduced into a form which a cell can understand and reciprocate likewise. The signal is often amplified before a response is sent and later the feedback pathways regulate the entire signalling process.

Salient features of Signal transduction:

There are 4 features of signal transduction:

1. Specificity: The signal molecule fits the binding site on its complementary receptor.
2. Amplification: When an enzyme activates another enzyme, the cascade mechanism increases the number of signal enzyme geometrically.
3. Desensitization: As soon as the receptor is activated, a feedback reaction is triggered that eventually switch off the receptor or remove it from the cell-surface association.
4. Integration: When 2 signals have an opposite effect on a metabolic characteristic such as the concentration of secondary messenger or membrane potential etc, the regulatory outcome is coming from the integrated input of both the receptors.