Chapter 11 Communication. Cell communication Traditional Ethiopian coffee ceremony.

transcript

Chapter 11

Communication

Cell communication

Traditional Ethiopian coffee ceremony

Caffeine

Sends signals to Blood vessels Brain Liver Heart

Yeast cells

Bacteria

Cell communication

Coordinates cell behavior Body functions as a whole. Hallmark of multicellular organisms. Evolution Single cell organisms communicate.

Cell communication

Cells are exposed to a continuous stream of signals.

Signals come from the environment surrounding the cell.

Signals can be from another cell. Chemical signals

Chemical signals

Peptides Proteins Amino acid Nucleotides Steroids or other lipids NO or Nitric oxide

Types of cell signaling

Depend on location of cells 1. Direct contact 2. Local signaling A. Paracrine signaling B.Synaptic signaling 3. Long-distance signaling Endocrine Nerve electrical impulse

1. Direct contact

Gap junction: Animal cells Plasmodesmata: Plant cells Chemical or electrical impulse

1. Direct contact

When cells are closeMolecules on one cell are

recognized by the plasma membrane of another cell.

Many interactions between cells in early development occur this way.

2. Local signaling

A. Paracrine signalingShort-lived signals with local

effects.Growth factorsPlay an important role in early

development

Local signaling

B. Synaptic signaling Involves the nervous systemNeurotransmitters: Signal moleculesChemical synapse: Communication be neuron & the

target cell

Long distance Signaling

Endocrine signalingMolecules that remain in the

extracellular fluid Enter the bloodstreamAffect cells very far from where

releasedHormones: longer-lived signal molecules

Long distance signaling

Nerve cellElectrical impulse along the

neuron

Signal transduction pathway

The signal causes a response in the cell

Fig. 11-14

Growth factor

Receptor

Phosphorylationcascade

Reception

Transduction

Activetranscriptionfactor

ResponseP

Inactivetranscriptionfactor

CYTOPLASM

NUCLEUS mRNA

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Reception:Signal is detectedMolecule binds a receptor

protein Located on surface or inside

Transduction:Signaling molecule changes

receptorChanges signal so it can cause a

responseSingle stepMultiple steps

Response:Stimulates a specific cellular

responseCorrect cellCorrect response

Reception

Ligand:Molecule that binds specifically to

another moleculeActivates the receptor proteinReceptor protein undergoes change

in shape

Reception

Most receptors are plasma membrane proteins

Signal (ligand) large, water soluble

Receptors

A. Intracellular receptors.B. Cell surface receptors.1. Ion-channel receptors2. Tyrosine kinases3. G-protein-coupled receptors

A. Intracellular receptors

Lipid-soluble signaling molecule Small molecule Able to cross the membrane Interacts with a receptor inside. Bind protein receptors in the cytoplasm Bind protein receptors in the nucleus

1. Act as regulators of gene expression

Activate or suppress expression of certain genes

Cortisol, testosterone, estrogen & progesterone are signal molecules.

Fig. 11-8-5 Hormone(testosterone)

EXTRACELLULARFLUID

Receptorprotein

Plasmamembrane

Hormone-receptorcomplex

NUCLEUS New protein

CYTOPLASM

2. Receptors act as enzymes Example: NO Binds a receptor. Activates the enzyme to catalyze the

synthesis of GMP Relax smooth muscle Causing blood vessels to relax Causes an increased blood flow

B. Cell surface receptors

Many signal molecules are water soluble Unable to pass through membrane Bind a receptor on the surface Causes a change inside cell.

B. Cell surface receptors

1. Ion channels (Chemically gated) Receptor proteins that allow ions to pass

through Opens only when a signal molecule (ligand)

binds to receptor. Ions are sodium, potassium, calcium or chlorine. Gate closes when ligand is released Example of signal molecule-neurotransmitter

2. Tyrosine Kinases

Single molecules bind receptor outside the cell

Stimulates receptor to activate the enzyme in the cytoplasm

These enzymes catalyze the transfer of phosphate groups

2. Tyrosine Kinases

Phosphorolated receptor Addition of phosphates to

receptorTriggers a cell responseCan trigger more than one

response

Fig. 11-7c

Signalingmolecule (ligand)

Ligand-binding site

TyrosinesTyr

Receptor tyrosinekinase proteins

CYTOPLASM

Signalingmolecule

Activated relayproteins

Cellularresponse 1

Cellularresponse 2

Inactiverelay proteins

Activated tyrosinekinase regions

Fully activated receptortyrosine kinase

6 6 ADPATP

G-protein coupled receptor

G-protein

GDP vs GTP

3. G-protein-linked receptors

G-protein Inactive: GDP (guanosine diphosphate) Active: GTP (guanosine triphosphate) Signal molecule binds the receptor Activates the receptor Activates the G-protein G-protein then initiates a series of events It can open an ion channel or stimulate an

enzyme

G-protein

It is a short lived response Dependent on continued extracellular

stimulation

Fig. 11-7b

G protein-coupledreceptor

Plasmamembrane

EnzymeG protein(inactive)

CYTOPLASM

Activatedenzyme

Cellular response

Activatedreceptor

GDP GTP

Signaling moleculeInactiveenzyme

Transduction

Relay of signals from receptors to target cell

Multiple stepsAmplify the signalCoordination of simple

processes

Transduction

Proteins (signal molecule)Phosphorylation cascadeTransfer a phosphate from an ATP to a

protein Enzyme: protein kinaseProtein causes cellular responseAbnormal kinase activity can result in

abnormal cell growth or cancer

Phosphorylation cascade

Inactivation

Protein phosphatasesEnzymes that remove phosphatesTurns off mechanismBalance of the

phosphorylation/dephosphorylation regulate activities of the cell

Second messengers

Non-protein, small, water-soluble molecules or ions

Diffuse quickly in the cytoplasmRelay messages from the receptor

to the target cellsG protein-coupled & tyrosine kinase

pathways

Second messengers

Cyclic AMP (cAMP) Cyclic adenosine monophophateCalcium ions

cAMP pathway

Signal molecule attaches to the surface receptor.

Activates the G receptor Activates the enzyme adenylyl cyclase to

make cAMP. cAMP then activates the target protein

cAMP pathway

Amplifies signalShort-livedPhosphodiesterases (enzyme)Converts cAMP to AMP

cAMP pathway

Cholera

BacteriaCauses diarrheaToxinBlocks the inhibitory enzymeG-protein remains active-Stimulates adenylyl cyclaseMakes excessive amounts of cAMPCauses intestines to secrete ions (salts)

Nitrates

Smooth muscle relaxationDilation of blood vesselsBlock the inhibitory enzyme Prolongs cGMPContinues affect

Calcium ions

Ca ion cytoplasmic levels usually low

Increased Ca levels can causeMuscle contractionCell divisionHormone release

Calcium ions

Signal molecule attaches to the surface receptor

Activates the G receptor Which activates the enzyme phospholipase

C. Which activates IP3

Which causes the ER to release Ca ions Ca ions cause affect

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Response

Regulation of a cellular activityNucleus or cytoplasmProtein synthesisActivity of a protein

Response

Fine-tuningAmplificationSpecificityScaffolding proteinHelps enhance response

Apoptosis

Programmed cell deathChop cells that are damagedProtects surrounding cellsEmbryonic cell growth

Fig. 11-19

Apoptosis

Caspase Enzymes that regulate cell deathSignal outside of cellNucleus can signal (DNA gone bad)ER (Protein misfolding)

Apoptosis

Webbed feet or handsParkinson’s or Alzheimer’sCancer (melanoma)

Fig. 11-21

Interdigital tissue 1 mm

Chapter 11 Communication. Cell communication Traditional Ethiopian coffee ceremony.

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