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32 Cell Communication
powerpoint lecture
20
Biology
Undergraduate 1
04/06/2011

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Term
What is a receptor tyrosine kinase?
Definition

a membrane receptor that attaches phosphate to tyrosines

 

they can trigger multiple signal transduction pathways at once (signal transduction is the conversion of an impulse or stimulus from one physical or chemical form to another. the process by which a cell responds to an extracellular signal)

Term
Receptor Tyrosine Kinases mostly activate what?
Definition

Ras which is a small G protein (a monomeric G protein)

It is membrane bound

Term
What pathway does Ras stimulate?
Definition

the MAP-kinase system

 

(mitogen-activated protein-kinase)

which stimulates cell division and growth

Term
Ion-channel coupled receptor
Definition
transmembrane receptor protein or protein complex that forms a gated ion channel that opens in response to the binding of a ligand to the external face of the channel 
Term

A type of membrane receptor...

Receptor tyrosine kinase

Definition
an enzyme coupled receptor in which the intracellular domain has a tyrosine kinase activity, which is activated by ligand binding to the receptor's extracellular domain
Term
Ligand-gated channel
Definition

an ion channel opens when it binds a small molecule such as a neurotransmitter

- it acts as a gate when the receptor changes shape 

Term
Ca2+ acts as a ___ ____ in many pathways. Why is it important?
Definition

secondary messenger

 

because cells can regulate its concentration

Term
What other secondary messengers are involved in the pathways that lead to the release of calcium?
Definition
inositol triphosphate (IP3) and diacylglycerol (DAG)
Term
Processing of visual information begins in the _____.
Definition
retina 
Term
the absorption of light triggers ___ ___ ___ in photoreceptor cells.
Definition
signal transduction pathway
Term
Define rods and cones. 
Definition

rods are light-sensitive but don't distinguise colors

 

cones distinguish colors but are not as sensitive to light

Term
what are the visual pigments that each rod and cone made up of?
Definition
a light-absorbing molecule called retinal bonded to a protein called an opsin
Term
what pigment do rods contain?
Definition

rhodopsin which is retinal combined with a specific opsin

 

it changes shape when absorbing light

Term
When light activates rhodopsin what happens?
Definition

cyclic GMP breaks down and Na+ channels close

 

this then hyperpolarizes the cell

Term
Initiation of apopotosis requires the conversion of ______ to mature _______.
Definition
procaspases and caspases 
Term
The proteolytic cascade leads to ____
Definition
apoptosis - programmed cell death
Term
Syndactyly
Definition
specific cells are not destroyed... webbed fingers
Term
What signals do cells need to avoid apoptosis?
Definition

survival factors (stimulate production of Bc12 that blocks apoptosis)

 

mitogens (mitogen is a chemical substance that encourages a cell to commence cell division, triggering mitosis

growth factors 

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