1.5 COMMUNICATION WITHIN MULTICELLULAR ORGANISMS Flashcards
How do multicelluar organisms achieve coordination?
Through extracellular signalling molecules, receptors and responses
What are receptor molecules?
Proteins in target cells with a binding site for a specific molecule
What effect does binding have on receptor molecules?
Conformational change
What is the result of a conformational change of a receptor molecule?
It alters the response of the cell
How is extracellular signalling specific?
Different cells produce specific signal molecules which can only be detected and responded to by cells with the specific receptors
In which type of organism is a tissue-specific response to the same signal possible?
Multicellular organisms
Where can receptors for hydrophobic signalling molecules be found?
In the cytoplasm or nucleus of their target cell
How is it possible that hydrophobic signalling molecules have receptors inside of the target cell?
They are lipid soluble
What does lipid soluble mean?
The substance can move through the plasma membrane
What can hydrophobic signalling molecules directly influence?
Transcription of genes
Give two examples of types of hydrophobic signalling molecules.
Thyroxine, steroid hormones
What is thyroxine?
A thyroid hormone
What does thyroxine hormone receptor bind to in the absence of thyroxine?
DNA
What is the result of thyroxine hormone receptor binding to DNA?
Inhibition of transcription of Na/KATPase gene
What is the result of thyroxine binding to its receptor?
Conformational change of thyroxine hormone receptor
What is the result of the conformational change to thyroxine hormone receptor?
Thyroxine hormone receptor can no longer bind to DNA
What happens when thyroxine hormone receptor cannot bind to DNA?
Transcription of Na/KATPase gene, increasing metabolic rate
What is the receptor protein for steroid hormones?
Transcription factor
What is the result of a steroid hormone binding to a transcription factor?
Transcription factor can bind to gene regulatory sequence of DNA
What happens when a transcription factor binds to a gene regulatory sequence?
Transcription occurs
Where are receptors for hydrophilic signalling molecules found?
At the surface of the cell
Give two examples of hydrophilic signalling molecules.
Peptide hormones, neurotransmitters
What happens to transmembrane receptors when a ligand binds outside of the cell?
Transmembrane receptors undergo conformational change
How is a hydrophilic signal transmitted across the membrane?
Signal transduction
What does signal transduction often involve?
Cascades of G proteins or phosphorylation by kinase enzymes
Name the two types of diabetes.
Diabetes mellitus and diabetes insipidus
Name the two types of peptide hormone.
Insulin and ADH
Where are receptors for insulin located?
Fat and muscle cells
What is the result of insulin binding to its receptor?
Recruitment of GLUT 4 glucose transporters triggered
Where are GLUT 4 glucose transporters recruited to?
Cell membrane of fat and muscle cells
What do GLUT 4 glucose transporters facilitate?
Uptake of glucose into fat and muscle cells
What causes type 1 diabetes?
Failure to produce insulin
What causes type 2 diabetes?
Loss of receptor function
Which type of diabetes (mellitus) is obesity usually associated?
Type 2
Other than insulin binding, what also triggers recruitment of GLUT 4 glucose transporters?
Exercise
Why is exercise recommended to sufferers of type 2 diabetes?
It triggers recruitment of GLUT 4 glucose transporter therefore increasing uptake of glucose to fat and muscle cells
Where are receptors for ADH located?
Collecting duct of kidney
What is the result of ADH binding to its receptor?
Recruitment of aquaporin 2 (AQP2)
What does aquaporin 2 do?
Provides efficient route for water to move across membranes
What does aquaporin 2 enable?
Control of water balance in terrestrial vertebrates
What causes diabetes insipidus?
Failure to produce ADH / Insensitivity of ADH receptors
