Unit 1: KA4 - Communication and Signalling Flashcards
What does communication in multicellular organisms involve?
Producing extracellular signalling molecules.
What effect does binding with a receptor have?
A conformational change in the receptor, which initiates a response within the cell.
What must cells possess to detect a signal?
A specific receptor.
Describe the term ‘tissue-specific response’
In a multicellular organism, different cell types may respond differently to the same signal molecule.
How do Hydrophobic signals bind to receptors?
Hydrophobic signal molecules diffuse through the phospholipid bilayer and bind with specific receptors in the cytosol or the nucleus to form the hormone-receptor complex.
Name the receptors for a hydrophobic signalling molecule.
Transcription factors.
What are transcription factors?
Proteins that when bound to DNA can either stimulate or inhibit initiation of transcription.
Name examples of hydrophobic signalling molecules.
Steroid hormones: Estrogen and Testosterone
What happens after the formation of the hormone-receptor complex?
It moves to the nucleus, where it binds to specific sites on DNA, influencing transcription.
What parts of DNA does the hormone-receptor complex bind to?
Hormone Response Elements (HREs)
How do hydrophilic signalling molecules bind to receptors?
Hydrophilic signalling molecules bind to transmembrane receptors and do not enter the cytosol.
Name examples of hydrophilic signalling molecules.
Peptide hormones
Neurotransmitters.
What happens to receptors after binding with hydrophilic signalling molecules?
A conformational change in the transmembrane protein.
How do transmembrane receptors act as signal transducers?
Transmembrane receptors act as signal transducers by converting the extracellular ligandbinding event into intracellular signals, which alters the behaviour of the cell.
What do transduced hydrophilic signals often involve?
G proteins
Cascades of phosphorylation by kinase enzymes
What is the function of G-proteins?
To relay signals from activated receptors to target proteins.
What is the function of a phosphorylation cascade?
To allow more than one intracellular signalling pathway to be activated (amplified signal).
What is the function of the peptide hormone insulin?
To create an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter to the membrane of fat and muscle cells.
Describe the differences in diabetes types.
Type one is caused by the failure to produce insulin.
type two is caused by the loss of receptor function.
Which diabetes type is generally associated with obesity?
Type two
What does exercise do for those with type 2 diabetes?
Can trigger the recruitment of GLUT4, therefore improving glucose uptake in fat and muscle cells.
What is resting membrane potential?
Resting membrane potential is a state where there is no net flow of ions across the membrane.
What is required for the transmission of a nerve impulse?
Changes in the membrane potential of the neuron’s membrane.
Define the term action potential.
An action potential is a wave of electrical excitation along a neuron’s plasma membrane.
