Unit 1.4 - 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
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
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 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
