Lecture 5 & 6 Questions Flashcards
List & define the 4 basic mechanisms of cell to cell communication. Give examples.
- Gap junctions - which allow direct cytoplasmic transfer of electrical & chemical signals b/t adjacent cells
- Contact-dependent signals - which occur when surface molecules on one cell membrane bind to surface molecules on another cell’s membrane
- Chemicals that diffuse through the extracellular fluid to act on cells close by (paracrine & autocrine)
Long distance communication (4) uses a combo of chemical & electrical signals carried by nerve cells & chemical signals transported in the blood
If 2 cells are connected by gap junctions, what happens to the second if the first has many more NA+/K+/ATPase
i think both would result in having an influx of Na+ and K+ because the cells are connected ??
What’s the difference between paracrine and autocrine?
paracrine: signaling to cells in the immediate vicinity
autocrine: signaling to self
Differentiate between a hormone, neurohormone and neurotransmitter. Which ones require action potentials?
hormone: are secreted by endocrine glands or cells into the blood
- only target cells with receptors for the hormone respond to the signal
neurohormone: are chemicals released by neurons into the blood for action at distant targets
neurotransmitter: are chemicals secreted by neurons that diffuse across a small gap to the target cell
Why don’t hormones affect all cells once they are released?
hormones come in contact with most cells of the body, but ONLY those cells with receptors for the hormone are target cells
What features do all signal pathways have?
- The signal molecule is a LIGAND that binds to a protein receptor
- the ligand is also known as a first messenger b/c it brings info to the target cell - Ligand-RECEPTOR binding activated the receptor
- The receptor in turn activates one or more INTRACELLULAR signal molecules
- The last signal molecule in the pathway creates a response by modifying existing proteins or initiating the synthesis of new proteins
Where are receptors located?
receptor proteins are located inside the cell or on the cell membrane
- target cell receptor proteins may be found in the nucleus, in the cytosol, or on the cell membrane as integral proteins
What are major classes of membrane receptors? Give an example of each.
- Receptor-channel
- allows Ca2+ into cells - Receptor-enzyme
ex: tyrosine kinase receptor (TKR or RTK) - G-protein-coupled receptor (GPCR)
ex: adenylyl cyclase or phospholipase C - Integrin receptor
ex: binds collagen
List them in order of fastest response to slowest response. Explain your choice.
fastest –> slowest
- receptor channel
- GPCR
What kind of receptors does testosterone bind to?
g
Can a receptor be an ion channel?
yes - receptor channels are ion channels too ?
What are the 2 main consequences of opening a receptor channel?
g
What are the main difference b/t a receptor enzyme & a G-protein coupled receptor? Which is more common. More complicated? Makes 2nd messengers? Shows more amplification?
receptor enzymes & GPCR both activate amplifier enzymes
results in signal amplification
- a small amount of ligand creates a large effect (the generation of a large # of intracellular molecules)
receptor enzyme:
- ligand binding to a receptor-enzyme activates an intracellular enzyme
G-protein couple receptors (GPCRs)
- activation of GPCR leads to generation/release of 2nd MESSENGERS
- sometimes the 2nd messengers are synthesized, sometimes they are released from a storage compartment
- small, diffusible (can be hydrophobic, hydrophilic, or a gas)
- stimulate a biological response
*- are a LARGE & COMPLEX family of membrane-spanning proteins that cross the phospholipid bilayer 7 times
*- G proteins linked to amplifier enzymes make up the bulk of all known signal transduction mechanisms
?
What’s an orphan receptor?
unknown functions
- b/c we simply don’t know what they do
Describe, in general terms, the process of g-protein coupled receptor signaling.
activation of GPCR leads to generation/release of 2nd messengers
- a 2nd messenger is a signaling molecule synthesized or released by a cell in response to an extracellular signaling molecule (hormone, for ex)
- -> sometimes they are synthesized, sometimes they are released from a storage compartment
- small, diffusible (can be hydrophobic, hydrophilic, or a gas)
- stimuluate a biological response