Communication and signalling Flashcards
What do multicellular organisms signal between?
Multicellular organisms signal between cells using extracellular signalling molecules.
What are receptor molecules of target cells?
Receptor molecules of target cells are proteins with a binding site for a specific signal molecule.
What happens when receptor molecules of a target cell bind to a specific signal molecule?
Binding changes the conformation of the receptor, which initiates a response within the cell.
What can only be detected and responded to by cells with the specific receptor?
Different cell types produce specific signals that can only be detected and responded to by cells with the specific receptor.
What happens in multicellular organisms (in relation to signalling)?
In a multicellular organism, different cell types may show a tissue-specific response to the same signal.
Can hydrophobic signalling molecules diffuse through the phospholipid bilayer?
Hydrophobic signalling molecules can diffuse directly through the phospholipid bilayers of membrane, and so bind to intracellular receptors.
What are the receptors for hydrophobic signalling molecules?
The receptors for hydrophobic signalling molecules are transcription factors.
What are examples of hydrophobic signalling molecules?
The steroid hormones oestrogen and testosterone are examples of transcription factors/hydrophobic signalling molecules.
Where do steroid hormones bind to?
Steroid hormones bind to specific receptors in the cytosol or the nucleus.
Where does the horomone-receptor complex move to?
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 hydrophobic signalling molecules bind to?
Hydrophobic signalling molecules bind to transmembrane receptors and do not enter the cytosol.
What happens when transmembrane receptors bind to a ligand?
Transmembrane receptors change conformation when the ligand binds to the extracellular face.
Does the signal molecule enter the cell when transmembrane receptors bind to a ligand?
The signal molecule does not enter the cell, but the signal is transduced across the plasma membrane.
What do transmembrane receptors act as?
Transmembrane receptors act as signal transducers by converting the extracellular ligand-binding event into intracellular signals, which alters the behaviour of the cell.
What involves G-proteins or cascades of phosphorylation by kinase enzymes?
Transduced hydrophilic signals often involve G-proteins or cascades of phosphorylation by kinase enzymes.
What do phosphorylation cascades allow?
Phosphorylation cascades allow more than one intracellular signalling pathway to be activated.
What does binding of a peptide hormone insulin to its receptor result in?
Binding of the peptide hormone insulin to its receptor results in an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells.
What is diabetes mellitus caused by?
Diabetes mellitus can be caused by failure to produce insulin (type 1) or loss of receptor function (type 2).
What is type 2 generally associated with?
Type 2 is generally associated with obesity.
What also triggers more recruitment of GLUT4?
Exercise also triggers recruitment of GLUT4, so can improve uptake of glucose to fat and muscle cells in subjects with type 2 diabetes.
What is the resting membrane potential?
The resting membrane potential is a state where there is no net flow of ions across the membrane.
What does the transmission of a nerve impulse require?
The transmission of a nerve impulse requires changes in the membrane potential of the neurons plasma membrane.
What is an action potential?
An action potential is a wave of electrical excitation along a neuron’s plasma membrane.
What do neurotransmitters initiate?
Neurotransmitters initiate a response by binding to their receptors at a synapse.
