Communication within Multicellular organisms Flashcards
Why is it essential that cells communicate within multicellular organisms?
In order to get required integration and co-ordination for cellular activities
What are the two principle forms of communication?
Hormonal
Nervous
Where are the receptor proteins for hydrophobic signals?
Within the cell/nucleus
Why do hydrophyllic signals require cell surface receptor proteins?
Cannot pass through the membrane
What are hormones?
Extracellular signalling molecules that are secreted by one tissue into the blood
What are the two types of hormones?
Hydrophobic and Peptide
Give examples of hydrophobic hormones?
Steroid Hormones
Thryoxine
Give examples of hydrophyllic hormones
Peptide Hormones, ADH, insulin
What are neurotransmitters?
Signals that are released into the synaptic gap between a nerve cell and its neighbour
What are the receptor proteins for steroid hormones?
Transcription factors
What is a transcription factor?
Protein that binds to DNA and controls the rate of transcription
Give an example of a steroid hormone
Testosterone, Oestrogen
What happens to the metabolism of a cell in the absence of thyroxine?
Metabolic rate is lower
What happens when thyroxine binds to its receptor protein?
Receptor undergoes conformational change
Can no longer bind to DNA
Gene for sodium potassium pump is transcribed
What are the two ways a cascade is activated once a hydropyllic signalling molecule binds to a receptor protein?
G proteins
Phosphorylation by Kinase Enzymes
Give examples of peptide hormones
Insulin
Glucagon
ADH
Somatrophin
What are G protein coupled receptors linked to?
A G protein
What is the difference between a G protein being on or off?
Whether GTP or GDP is attached
What happens when a hydrophyllic signalling molecule binds to the extracellular side of GPCR?
GTP replaces GDP and the G protein becomes active
What happens when a G protein is active?
G protein stimulates enzymes leading to a response in the cell
Why is the response only temporary if the G protein triggers the response?
G protein is a GTPase and hydrolyses the GTP into GDP making the G protein inactive again
What does RTK stand for?
Receptor Tyrosin Kinases
What happens when a ligand binds to a RTK?
Tyrosine amino acids on the receptor becomes phosphorylated and a conformational change occurs
Kinase domains in the receptor becomes active and this results in the phosphorylating of downstream molecules
What does the response of the cell depend on?
Depends on the signal
Give examples of possible responses of the cells
Recruitment of a channel
Transcription of certain genes
What is the insulin receptor?
Kinase linked receptor
Where is the insulin receptor found?
Cell membrane of fat and muscle cells
What happens once insulin binds its receptor?
Signal is transduced and a series of phosphorlyation events trigger the recruitment of GLUT4 to the cell membrane
What does GLUT4 allow?
Allows glucose to enter the cell
What is Diabetes Mellitus?
Medical Condition caused by a failure at some stage of insulin signalling pathway
What is the difference between Type 1 and Type 2 diabetes?
Type 1 - Failure to produce insulin
Type 2 - Loss of receptor function
How is type 1 diabetes treated?
Injections of Insulin
How does exercise improve type 2 diabetes?
Triggers recruitment of GLUT4
Where is ADH secreted from?
Pituitary gland
When is ADH secreted?
In response to low blood water concentration
What is the receptor protein for ADH?
G protein coupled receptor
Where is the receptor protein for ADH located?
Membrane of cells in the collecting ducts of the kidney tubules
What happens when ADH binds to its receptor?
Triggers multiple cascades of reactions
Activates G proteins which trigger these cascades and amplify the signal
What is the response of the cell when ADH binds?
Recruitment of the channel protein Aquaporin 2 (AQP2) to the membrane
What does the recruitment of AQP2 allow?
Control of water balance in terrestrial vertebrates
What can failure to recruit AQP2 or insensitivity of the receptor result in?
Diabetes Insipidus
Diabetes insipidus results from failure to recruit water channel proteins to the cell membrane.
Identify the cause of recruitment failure
Failure to produce ADH
