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
Do hydrophilic signal molecules enter the cell?
Does not enter the cell, instead it is transduced across the membrane
What are 2 possible outcomes of hydrophilic signals being transduced?
Cascades of G-proteins
Phosphorylation by kinase
How is a signal transduced using G-protein linked receptors?
Signal molecule binds to a receptor and the receptor changes conformation
Causes GDP to be replaced with GTP which activates the G-protein
This activates another enzyme which generates a cellular response
How is a signal transduced using phosphorylation?
Ligand binds to receptor tyrosine kinases (RTKs)
Causes amino acids on the receptor to become phosphorylated resulting in conformational change in receptor
Activating the kinase domains in the receptor and phosphorylating downstream cytoplasmic molecules resulting in various cellular responses
What type of signalling molecule is insulin
Hydrophilic signal molecule
Where are insulin receptors found?
Surface of the cell
What triggers the recruitment of GLUT4 glucose transporter to the cell membrane?
The binding of insulin to its receptor
What is the name of the glucose transporter?
GLUT4
Name 2 cell types that contain GLUT4?
Fat cells
Muscle cells
What is the function of glucose transporter?
Allow glucose to pass across the plasma and enter the cell
What condition is caused when insulin is not produced?
Type 1 diabetes
What condition is caused by receptors of insulin failing to respond?
Type 2 diabetes
What is the main cause of type 2 diabetes?
Obesity
Why is exercise used to treat type 2 diabetes?
Exercise triggers recruitment of GLUT4 so can improve uptake of glucose to fat and muscle cells in subjects with type 2 diabetes
What does the up take of glucose depend on?
Insulin being present
What type of signal molecule is ADH?
Hydrophilic signalling molecule
Where are ADH receptors located?
Collecting duct of the kidney
How does ADH recruit water transporter?
ADH binds to its receptors on the cells collecting ducts causing a cell transduction process which results results in the recruitment of channel protein aquaporin 2 to the membrane of cells
Name the water transporter
Aquaporin 2
What is the function of aquaporin 2?
Provides a highly efficient route for water to move across membranes.
Recruitment of aquaporin 2 allows control of water balance in terrestrial vertebrates
What condition results from failure to produce ADH/ insensitivity of receptor?
Diabetes insipidus