Key Area 5: Comunication within Multicellular Organisms Flashcards
What are three stages of coordination?
Signalling molecules
Receptors
Responses
What happens when a signal binds to a receptor?
Conformational change
How do different cells respond differently to signals?
The receptors the cell contains
Where are the receptors for hydrophobic signals found?
Within the cell or nucleus
How do hydrophobic signals pass through the membrane?
Easily because of their hydrophobic nature
What are two examples of hydrophobic signal molecules?
Thyroxine and steroid hormones
What is a transcription factor?
A protein that initiates the transcription of DNA to mRNA
What are thyroid hormones used for?
To control transcription of the sodium-potassium pump
Describe how thyroid hormones are used to control the transcription of the sodium potassium pump
Thyroxine binds to receptor causing conformational change leading to de-binding of DNA and allowing transcription
In the absence of thyroxine, thyroid receptors bind to DNA preventing transcription
What receptor protein does steroid hormones bind to?
Transcription factor
How do steroid hormones regulate transcription?
By binding to their receptor and switching on/off the gene
Where are receptors for hydrophilic signals found?
On the cell surface
What are examples of hydrophilic signal molecules?
Peptide hormones
Neurotransmitters
What are the three stages of communication?
- reception
- transduction
- response
What happens during reception?
Signal molecule binds to receptor protein
What happens during transduction?
Conformational change of protein followed by activation of other molecules and amplification of signal
What happens during response?
Activation of some other cellular response
How do hydrophilic signal molecules move across the membrane?
They don’t enter the cell, the hydrophilic signal is transducer across the membrane
What are two possible outcomes of hydrophilic transduced signals?
- cascades is G-proteins
- phosphorylation by kinases
Describe how G-protein linked receptors work
g-protein linked receptor becomes activates when a signal molecule binds, which changes confirmation of the receptor so jt can activate the G-protein. GTP displaces GDP and a further protein enzyme is activated which triggers a response
Describe how phosphorylation works?
Membrane protein receptor tyrosine kinases (RTKs) are activates by binding of signal molecules. Kinases carry out phosphorylation of tyrosine amino acids on receptor followed by a series of phosphorylation of other cytoplasmic molecules. Eventually a protein will be activated that induces a cellular response such as transcription of a particular gene.
How are signals amplified in phosphorylation by kinases?
Phosphorylation cascades amplifies signals
What is insulin?
Peptide hormone
Where are insulin receptors found?
Fat and muscle cells
