Unit 1 - section 5 Flashcards
What are 3 things that allow coordination to be achieved in multicellular organisms?
Signalling molecules
Receptors
Responses
What is the basic role of signalling molecules, receptors and responses in coordination?
Signalling molecules - molecules that bind to specific receptors
Receptors - protein with binding site for specific signal molecule
Responses - occur due to an alteration of receptor conformation
What is the effect of a signal molecule binding to a receptor?
Changes the conformation of the receptor. This can alter the response of the cell
What is the significance of multicellular organisms containing many different cell types in the production, receipt and response to signals?
Different cell types produce specific signals which can only be detected and responded to by cells with the specific receptor. In a multicellular organism different cell types may show a tissue specific response to the same signal (two cells can respond differently to same signal)
Where are the receptors of hydrophobic signals found?
Within the cells or even within the nucleus of a cell
How do hydrophobic signals cross the membrane?
Can easily pass through the phospholipid membrane due to their hydrophobic nature
What are 2 example of hydrophobic signalling molecules?
Thyroxine
Steroid hormones
What is a transcription factor?
A protein which binds to DNA and controls rate of transcription. Can enhance or block the binding of RNA polymerase to specific genes which controls whether the gene is transcribed or not
How are thyroid hormones used to control the transcription of the sodium potassium pump?
Thyroid hormone receptor protein binds to DNA in the absence of thyroxine and inhibits transcription of the gene for the sodium potassium pump. When thyroxine binds to the receptor protein, conformational change prevents the protein binding to the DNA and transcription of the gene for the sodium potassium pump can begin, raising metabolic rate
What is the type of receptor protein that steroid hormones bind to?
Transcription factor proteins
How do steroid hormones regulate transcription?
Only once the steroid hormone has bound to the receptor can the transcription factor bind to gene regulatory sequences of DNA for transcription to occur
Where are receptors for hydrophilic signals located?
On the cell surface
Give 2 examples of hydrophilic signalling molecules
Peptide hormones
Neurotransmitters
What are the 3 stages in communication?
Reception - signal molecule binds to the receptor protein
Transduction - conformational change of a protein followed by the activation of other molecules and amplification of the signal
Response - activation of some other cellular response eg transcription, movement of cytoskeleton
What is the effect of the binding of a signal molecule to a receptor?
A conformational change
