Communication and Signalling Flashcards
What do multicellular organisms use to signal between cells?
Extracellular signalling molecules
Examples of extracellular signalling molecules?
Steroid hormones, peptide hormones and neurotransmitters
What are receptor molecules of target cells?
proteins with a binding site for a specific signal molecule
What does binding to a receptor molecule do?
binding changes the conformation of the receptor, which initiates a response within the cell
What do hydrophobic signalling molecules do?
diffuse directly through the phospholipid bilayer and 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 stimulate or inhibit initiation of transcription
Examples of hydrophobic signalling molecules?
The steroid hormones oestrogen and testosterone
Where do steroid hormones bind?
specific receptors in the cytosol or the nucleus
What does the Hormone-Receptor complex do once in the nucleus?
it binds to specific sites on DNA and affects gene expression
What does the hormone-receptor complex bind to?
specific DNA sequences called hormone response elements (HREs)
What does binding at HRE’s influence?
Influences the rate of transcription
What do hydrophillic signalling molecules do?
Bind to transmembrane receptors and do not enter the cytosol
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
Examples of hydrophillic extracellular signalling molecules?
Peptide hormones and neurotransmitters
What are phosphorylation cascades?
Involve a series of events with one kinase activating the next in the sequence and so on
What do phosphorylation cascades allow?
allow more than one intracellular signalling pathway to be activated
What does the binding of the peptide hormone insulin to its receptor result in?
an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells
What can diabetes mellitus be caused by?
failure to produce insulin (type 1) or loss of receptor function (type 2)
Type 2 diabetes is generally associated with…
obesity
What else triggers recruitment of GLUT 4?
Exercise
What do G-proteins do?
G-proteins relay signals from activated receptors to target proteins such as enzymes and ion channels
what does the binding of insulin to its receptor cause?
a conformational change that triggers phosphorylation of the receptor
binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. This starts _____
a phosphorylation cascade inside a cell, which eventually leads to GLUT4 containing vesicles being transported to the cell membrane
What is resting membrane potential?
A state where there is no net flow of ions across the membrane
What does the transmission of a nerve impulse require?
changes in the membrane potential of the neuron’s plasma membrane
What is an action potential?
A wave of electrical excitation along a neuron’s plasma membrane
How do neurotransmitters initiate a response?
by binding to their receptors at a synapse
What are neurotransmitter receptors?
ligand-gated ion channels.
What is depolarisation?
A change in the membrane
potential to a less negative value inside.
What is the retina?
the area within the eye that detects light and contains two types of photoreceptor cells: rods and cones
In animals the light-sensitive molecule retinal is combined with….
a membrane protein, opsin,
to form the photoreceptors of the eye
Rods function in _____ _______ but do not allow _____ __________.
dim light, colour perception
What are cones are responsible for?
colour vision and only function in bright light
