Communication And Signals Flashcards
What can signalling molecules be
Hydrophobic (transcription)
Hydrophilic (transduction)
Neurotransmitters (nerve impulses)
Describe hydrophobic signalling
Hormone diffuses through phospholipid bilayer and binds to receptor in cytosol
Receptor travels to nucleus and binds to DNA where it can either inhibit or stimulate transcription
Protein synthesis altered
What are the receptors in hydrophobic signalling called
Transcription factors
Examples of hydrophobic signalling molecules
Steroid hormones such as oestrogen and testosterone
What happens when steroids bind to receptors in the cytosol
Forms hormone receptor complex
What do hormone receptor complexes do
Move to nucleus, bind to specific DNA sequences called Hormone response elements
-influences transcription
What happens to hydrophilic signalling molecules in the beginning
Do not enter cytosol
Bond to transmembrane receptors
Give examples of hydrophilic signalling molecules
Peptide hormones
Insulin
Neurotransmitters
What happens when hydrophilic signal molecules bind to receptors
Conformation changes
-creates intracellular signal which alters behaviour of cell
What are transmembrane receptors described as
Signal transducers
WHat do G proteins do
relay signals from activated receptors to target proteins (enzymes or ion channels)
What do phosphorylation cascades do
allow more than 1 signalling pathway to be activated
WHat happens during a phosphorylation cascade
activates a kinase which then activates the next kinase and so on
What does the hydrophilic signalling molecule insulin do
triggers recruitment of GLUT 4 proteins to cell membranes of fat and muscle
resulting conformational change causes phosphorylation of receptor and triggers cascade
What does the insulin phosphorylation cascade do
vesicles containing glut 4 are transported to my membrane and allow glucose to enter the cell
What else triggers the recruitment of glut 4
excercise
WHat is resting membrane potential
no net flow of ions across the membrane
What is action potential
wave of eletrical excitation along a neuron’s plasma membrane
Are neurotransmitters hydrophobic or hydrophillic
hydrophilic
What is depolarisation
makes plasma membrane less negative
(NA enters)
What is repolarisation
Makes plasma membrane more negative
(K leaves)
What happens when a neurotransmitter binds to a receptor
ligand gated ion channels open
What happens when a patch of membrane gets depolarised
neighboring regions of membrane depolarise and go through the same cycle
What does the retina do
detects light
What photoreceptor cells does the retina have
rods
cones
When do photoreceptor cells function
rods in dim light
cones for colour vision
What does retinal combine with to produce
opsin
forms photoreceptors in eyes
What does opsin do in cone cells
different forms of opsin combine with retinal to produce photoreceptor proteins
What is the retinal ospin complex called
rhodopsin
How many photons of light will retinal absorb
1
what happens to rhodopsin when a photon of light is absorbed
becomes photoexcited rhodopsin
What does photoexcited rhodopsin do
activates HUNDREDS of the G protein called transducin
WHat does transducin do
activate 1 molecule of PDE
What does PDE do
catalyses the hydrolysis of thousands of cyclic GMP (cGMP)
What happens when cGMP concentration decreases
ion channels close and build up of ions causes hyperpolarisation, triggering impulses around the retina
