Communication and Signalling Flashcards
What is a receptor molecule?
Receptor molecules of target cells are proteins with a binding site for specific signal molecules
Do all cell types respond in the same way to the same hormone? Explain.
Signalling molecules may have different effects on different target cell types due to differences in the intracellular signalling molecules and pathways that are involved.
Hormones circulate in the blood. Why do only some cell types show a response to the presence of the hormone?
Different cell types produce specific signals that can only be detected and responded to by cells with the specific receptor.
What are 3 examples of extracellular signalling molecules?
Steroid hormones - peptide hormones - neurotransmitters
What happens when an extracellular signal molecule binds to a receptor molecule?
Binding changes the conformation of the receptor, which initiates a response within the cell.
What is a hormone response element?
The DNA sequences where the hormone-receptor complexes bind.
What are transcription factors?
Transcription factors are proteins that when bound to DNA can either stimulate or inhibit initiation of transcription.
What is the process of hydrophobic signalling in target cells?
Steroid hormones bind to specific receptors in the cytosol or the nucleus. The hormone-receptor complex moves to the nucleus where it binds to specific sites on DNA and affects gene expression. The complex binds to specific DNA sequences called hormone response elements (HREs)
What are 2 examples of hydrophobic signalling molecules?
Testosterone - oestrogen
How can the same hormone be responsible for inhibiting or initiating the transcription of multiple genes?
The hormone then activates different transcription factors and therefore regulates the transcription of different genes by binding to different HREs.
What is a phosphorylation cascade and what effect will it have within the cell?
Phosphorylation cascades allow more than one intracellular signalling pathways to be activated. Phosphorylation cascades involve a series of events with one kinase activating the next in the sequence and so on. Phosphorylation cascades can result in the phosphorylation of many proteins as a result of the original signalling event.
What are 2 examples of hydrophilic signalling molecules?
Peptide hormones - neurotransmitters
What role do G-proteins play in signal transduction?
G-proteins relay signals from activated receptors (receptors bound to a signalling molecule) to target proteins such as enzymes and ion channels.
What is the process of transduction of a signal by hydrophilic signalling molecules?
Transmembrane receptors change conformation when the ligand binds to the extracellular face; the signal molecule does not enter the cell, but the signal is transduced across the plasma membrane. Transmembrane receptors act as signal transducers by converting the extracellular ligand-binding event into intracellular signals, which alters the behaviour of the cell.
Why is the neurotransmitter receptor protein described as a ligand-gated channel?
Ligand-gated ion channels are transmembrane receptor complexes that conduct ion flow through channel pores in response to the binding of neurotransmitters. Unlike voltage-gated ion channels, these receptors are typically not sensitive to membrane potentials.
