BSCI 171: Cell Communication

Exam 2 materal

signaling between adjacent cells

• juxtacrine

  • “just right next to”

signaling between nearby cells

• paracrine signaling

synaptic signaling

electrical signal triggers release of neurotransmitter

signaling between distant cells

• endocrine signaling

  • signaling cell sends singaing molecule that travels to target cell

Only cells with __ tuned to a specific signal will receive the signal sent by another cell

receptor

In what ways do cells respond to signals?

through changes in cellular activity

• ex.) enzyme activity, gene expression, cell division

ligand

signaling molecule

most chemical signals are ___

hydrophilic

• means they cannot pass through membrane without help

most receptors are ____

transmembrane proteins

• interact on both in and out of membrane

Lipid soluble signals (hyrdrophobic)

• pass through plasma membrane and bind to specific receptor in cytoplasm or in nucleus

• activated receptor-ligand complex regulates genes by binding DNA

Water soluble signals (hydrophilic)

• cannot pass through membrane

• bind to specific plasma membrane receptors

• eceptor-ligand complex activates cascade of events in cell

intracellular signaling: receptors are found in the ___ or ___

cytiplasm or nucleus

intracellular signaling: signal must be ___ or ___ to diffuse through membrane

hydrophobic or very small

membrane bound receptors

interact with hydrophilic signals

• ligand gated

• G protein coupled

• enzyme linked

Ligand gated receptors

• channels that open to allow things to move into them

G Protein coupled receptor

• need transmembrane protein

• GDP becomes phosphorylated to activate G protein

• G protein interacts with effector protein

Enzyme linked receptors

linked to enzymatic activivty

signal transduction pathway

series of steps that eventually leads to biochemical response

the intermediate steps in signal transduction involve _____ of enzymes

activation or inactivation

• most common step is addition or removal of phosphate group

Protein kinase

enzyme that helps add phosphate group from ATP to a protein

protein phosphatase

enzyme that helps remove phosphate groups from proteins

Second messengers

• part of signal transduction

• they’re activated by the initial signal & carry instructions through cell

Cyclic AMP

• common second messenger

• produced by cells in response to several different hormones

• generaed from ATP from adenylyl cyclase

  • 2 phosphate groups removed frmom adenylyl cyclase

phosphodiesterase

breaks down cAMP back to AMP

What kind of responses is seen in the nucleus?

changes in gene expression

What kind of responses is seen in the cytoplasm?

changes in:

• enzyme activity

• motor activity

• cytoskeletal structure

fine tuning of response can lead to:

• amplification: small signal leads to large response

• regulation:

• termination:

How can different cells respond to the same signal differently?

• different receptors

• different intermediate proteins

• different final targets