Communication and Signalling Flashcards
Name 3 extracellular signalling molecules
Steroid hormones
Peptide hormones
Neurotransmitters
In a multicellular organism, different cell types may show…
a tissue specific response to the same signal
Why do signalling molecules have different effects on different target cell types
due to differences in the intracellular signalling molecules and pathways that are involved
Hydrophobic signalling molecules do what
diffuse directly through the phospholipid bilayers of membranes, and so bind to intracellular receptors
What are the receptors for hydrophobic signalling molecules
transcription factors
What are transcription factors
proteins that when bound to DNA can either stimulate or inhibit initiation of transcription
Name 2 steroid hormones
Oestrogen
Testosterone
Where do steroid hormones bind to their receptors
bind to specific receptors in the cytosol or the nucleus
Expand on “The hormone-receptor complex moves to the nucleus where it binds to specific sites on DNA and affects gene expression”
The hormone-receptor complex binds to specific DNA sequences called Hormone response elements (HREs). Binding at these sites influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes.
Where do hydrophilic signalling molecules bind
bind to transmembrane receptors and do not enter the cytosol
name 2 hydrophilic extracellular signalling molecules
Peptide hormones
Neurotransmitters
What happens when hydrophilic signalling molecules bind to a transmembrane receptor.
The conformation of transmembrane receptor changes. The signal molecule does not enter the cell but is transduced across the plasma membrane.
How do transmembrane receptors act as signal transducers
by converting the extracellular ligand-binding event into intracellular signals, which alters the behaviour of the cell. Often involves G-proteins or cascades of phosphorylation by kinase enzymes
What do G-proteins do
G-proteins relay signals from activated receptors to target proteins such as enzymes and ion channels
What happens when the peptide hormone insulin binds to its receptor
results in an intracellular signalling cascade that triggers the recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells..
