ch 16

second messenger

small, diffusable, soluble ions seving as an internal signal

-> relays & amplifies signal within cell

-> usually activated kinase

What is the end result of activation of surface receptors?

phosphroylation of proteins

How do you phosphorylate a protein?

protein kinase, acts as a switch

What removes phosphate?

phosphatase, inactivates the protein

What are the three classes/types of cell surface receptors?

Enzyme-coupled receptor

G protein-coupled receptor

Ion channel-coupled receptor

Enzyme Coupled Receptor

DIRECTLY alter enzyme's activity (typically dimers)

e.g insulin, growth factors

-- cGMP

Transduction

the process by which a cell converts an external signal (like hormones or neurotransmitters) into a specific functional response, such as growth, division, or gene expression

G Protein Coupled receptor

Activates a G protein. Works through G-protein to activate enzyme

e.g glucagon, adrenaline, acetylcholine

--> cAMP IP3 DAG Ca++

Ion channel-coupled receptor

ligand-gated channel

located in neuron or muscle cell

- no second messanger

- changed membrane potential

- ligand: neurotransmitter

How does an Ion-channel receptor work?

signal binds to receptor, opening it and permitting ion to move through

What are the four basic types of cell signaling?

Endocrine, Paracrine, Neuronal, Contact dependent

What is endocrine signaling

cells release signals that travel long distances to affect target cells

eg. horomones travel by blood, every cell can do this

paracrine signaling

Signal released from a cell has an effect on neighboring cells.

local mediators, not by blood

Neuronal signaling

occurs within the cells of the nervous system and involves the release of hormones into localized areas of the nervous system called synapses.