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18 Cards in this Set

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What are three examples of effector protein?
1. Metabolic enzyme - alters metabolism
2. Gene regulatory protein - alters gene expression
3. Cytoskeletal protein - alters cell shape or movement
What are gap junctions?
- narrow water filled channels that allow neighbouring cells to communicate directly
- exchange inorganic ions and small water soluble molecules
- formed by 2 connexons each composed of 6 subunits
What are three ways of releasing signal molecules into the extracellular space?
1. Exocytosis
2. Diffusion through membrane
3. Attached to extracellular surface of cell
What is required for a cell to respond to a signal?
a receptor
Are you losing your mind yet?
YES!!!!
How does an intracellular receptor work?
- signal is brought to the cell by a carrier protein and then signal enters the cell and goes to the intracellular receptor, often on the nucleus to control transcription
- signal must be small and hydrophobic since it has to diffuse across the membrane
Where are most signal receptors located?
on the cell surface
What does the nuclear receptor superfamily do?
- control transcription
- bind to specific DNA sequences and activate transcription
- some require binding of ligand
How many nuclear receptors are there in humans?
in humans there are about 48 nuclear receptors
What are the three classes of cell surface receptors?
1. Ion-channel coupled receptors - transmitter gated ion channels
2. G-protein coupled receptors - inactive receptor and inactive G-protein are coupled and activated by a signal molecules which in turn allows the activation of associated membrane
3. Enzyme-coupled receptors - signal molecule activates receptor which in turn directly activates an enzyme
What are the two types of short distance signaling?
1. Contact dependent - membrane bound signal molecules and receptor on two different cells come together
2. Paracrine - signal is released to the outside by exocytosis or diffusion and acts locally
What is the difference between paracrine and autocrine?
Paracrine - signaling cell and target cell are different type
Autocrine - they are the same type
What four ways can a paracrine signal act and what controls this?
1. Signal taken up rapidly by target cells
2. Can be destroyed in ECM
3. Can be immobilized by ECM
4. Can have antagonists that bind to signal molecule or receptors that then prevent further minding
- this is all to make sure it only acts locally
- and these are all controlled by a local mediator
What are the two types of long distance signaling?
1. Synaptic - very fast, electric pulses 100 m/sc
- high local concentration of neurotransmitter

2. Endocrine - hormone released into blood stream, much more slow, low concentration of hormones
What types of cell signaling responses are Slow (minutes to hours) and what types are Fast (seconds to minutes)?
Slow: cell growth and division which require changes in gene expression, also the synthesis of new proteins

Fast: cell movement, secretion, metabolism
How does primary and secondary transcriptional responses work?
- Signal comes in which causes activation of primary response genes
- these in turn induce synthesis of primary response proteins
- these proteins then may activate a secondary response or cause negative feedback in which primary response genes are shut down
What happens if there are no signals received by cells?
apoptosis
What are ways for the same signal to have different responses?
- different receptors can cause different responses
- so can different intracellular signaling proteins becuase they cause different cascades
- different effector proteins
- different activated genes
- and different concentration of a signal