Bio - Unit 6 part 1
why do cells need to communicate with each other (4)
1. Multicellular organisms coordination of development (from single cell to trillions of cells
2. growth
3. coordinating whole body growth and development with environment
4. day to day physiology
Long range communication vs short range communication in animal cellls (3)
1. endocrine: signal that travels via blood, any range, signal molecule diffuses into blood, Signal is broadcast through the entire body. One cell with the receptors can hear the signal
2. Neuronal: neuron sends long signal, tiny diffusion component, tight connection. Signal is sent directly to the receptor
3. Paracrine: all about diffusion, once cell releases a signal that diffuses into target cells
What is the Signalling Pathway (5)
1. singalling molecule synthesized and released by signaling cell
2. signal molecule travels to target cell
3. signal binds to receptor protein on/in target cell
4. changes in protein activity (activation inactivation), changes in gene expression
5. Changes in cell behaviour
- the same signal can cause different responses depending on the target cell
How is cell behaviour diven by multiple signals
cell needs multiple signals to survive, grow and divide
How is the location of the receptor predicted
1. cell surface receptors (hydrophillic signal molecule)
2. Instracellular receptors (hydrophobic signal molecule)
How do hydrophobic signal molecules enter the cell
small hydrophobic signal molecules typically enter the cell and bind to receptors that regulate gene transcription (steroids).
Steroid hormone mechanism of action
- steroids receptors are members of nuclear receptor family of transcription factors
- steroids will help activate transcription of a target gene
Where do signals bind to the receptor protein (steroids)
They bind on the plasma membrane
what is a second messenger
Small non protein molcules that relay signals from receptors to target molecules within a cell
What do intracellular signal molecules act as
they act as molecular switches
Regulations of proteins by phosphorylation (3)
1. each activation step in a cascade needs to be inactivated
2. activity of a protein regulated by phosphorylation depends on balance between activities of its kineses and phosphatase
3. Many proteins regulated by phosphorylation are themselves kinases phophosylation cascades,
what are the three classes of cell surface receptors
1. ion channel linked
2. GPCRs
3. enzyme links
What are ion channel coupled receptors (2)
1, binding of ligand (signal molecule) opens (or closes) ion channel
2. flow of ions (inward or outward) changes voltage across membrane. Aka neurotransmitter - gated channels and ligand gated channels
what are cell-surfaced receptors (3)
1. G protein coupled receptors (GPCRs)
2. binding of ligand activates trimeric GTP-binding proteins ( G proteins), which in turn activate an enzyme or ion channel in membrane to set off cascade
3. about half of all knows drugs act via GPCRs
What are enzyme coupled receptors (2)
1. receptors are enzymes themselves or associated with enzymes
2. signal molecule in for of dimer activates the catalytic domain