Hydrophobic And Hydrophilic Signals Flashcards
How do multicellular organisms signal between cells
By using extracellular signalling molecules
What are examples of extracellular signalling molecules
- Steroid hormones (oestrogen + testosterone)
- Peptide hormones
- neurotransmitters
What are receptor molecules of target cells - what are receptors
Proteins with binding site for specific signal molecule
What initiates a response within a cell
Binding which changes the conformation of the receptor
What type of response would show in a multicellular organism
Tissue-specific response to same signal
What can hydrophobic signals do
Diffuse directly through phospholipid bilayer of membrane and bind to intracellular receptors
What are the receptors for hydrophobic signalling molecules
Transcription factors
What are transcription factors
Proteins which when bound to DNA can either inhibit or initiate transcription
Examples of hydrophobic signalling molecules
- oestrogen
- testosterone
What do steroid hormones bind to
Specific receptors in the cytosol or nucleus
What are hormone response elements (HREs)
HREs are what hormone-receptor complexes binds to on specific DNA sequences
What does binding at hormone response elements (HREs) cause
- It can influence rate of transcription
- affects gene expression
Hydrophilic signalling
Hydrophobic signalling molecules bind to transmembrane receptors and do not enter cytosol
What are examples of hydrophilic signalling molecules
- peptide hormones
- neurotransmitters
When do transmembrane receptors change conformation
When ligand binds to the extracellular face and the signal is transduced across the plasma membrane
How do transmembrane receptors act as signal transducers
By converting the extracellular ligand-binding event into intracellular signals —> alters behaviour of cell
Function of G-proteins
G-proteins relay signals from activated receptors to target proteins like enzymes and ion Channels
What do transduced hydrophilic signals involve
Often involve G-proteins or cascades of phosphorylation by kinase enzymes
What do phosphorylation cascades allow
Allow for more than one intracellular signalling pathway to be activated
What is a phosphorylation cascade
Involves a series of events with one kinase activating the next in sequence
What is the result of the peptide hormone insulin binding to receptor
Results in intracellular cascade -> triggers recruitment of GLUT4 glucose transporter proteins to cell membrane of fat and muscle cells
Causes of diabetes Mellitus
- Type 1 - failure to produce insulin
- type 2 - loss of receptor function and sensitivity (linked with obesity)
What triggers the recruitment of GLUT4
Exercise which improves uptake of glucose to fat and muscle cells (type 2)
