AH Biology - Unit 1 - KA4(c) - Hydrophilic Signals and Transduction

What are key examples of hydrophilic signals?

Key examples of hydrophilic signals are peptide hormones, such as insulin, and neurotransmitters.

What do hydrophilic signalling molecules do?

Hydrophilic signalling molecules cannot diffuse through membranes and bind to transmembrane receptors. They do not enter the cytoplasm, instead, the signal is transduced across the plasma membrane. Transmembrane receptors change conformation when the hydrophilic signal molecule, a ligand, binds to the extracellular face, the membrane on the outer surface of the cell.

What do transmembrane receptors act as?

Transmembrane receptors act as signal transducers. This means that they convert the extracellular ligand-binding event into an intracellular signal which alters the behaviour of the cell and brings about a response.

What do transduced hydropholic signals often involve?

Transduced hydrophilic signals often involve:

• G-proteins

and/or

• Phosphorylation cascades by kinase enzymes

What do G-proteins do?

G-proteins relay signals from activated receptors to target proteins, such as enzymes or ion channels.

What do phosphorylation cascades involve?

Phosphorylation cascades involve a series of events with one kinase activating the next in the sequence and so on. More than one intracellular signalling pathway can be activated in this way. This phosphorylation can result in the phosphorylation of many proteins as a result of one original signalling events.

What

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