john girard project opening doors. chemical “messengers” cells communicate by chemical...

Cell Communication

John GirardProject Opening Doors

Cells communicate by chemical “messengers”

Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells

In local signaling, animal cells and unicellular organisms may communicate by direct contact, called cell-cell recognition

Cell Communication

Animal cells communicate using local regulators, messenger molecules that travel only short distances

In long-distance signaling, plants and animals use chemicals called hormones

Cell Communication

Local and Long-Distance Cell Communication in Animals

Communication by Direct Contact between Cells

A signal transduction pathway is a series of steps by which a signal on a cell’s surface is converted into a specific cellular response

Cells receiving signals go through three processes:

Reception Transduction Response

Cell Communication

Overview of Cell Signaling

Receptors in the Plasma Membrane

There are three main types of membrane receptors:

G protein-coupled receptors

Tyrosine kinase receptors

Ion channel receptor

The Structure of a G-Protein-coupled Receptor

The Functioning of a G-Protein-coupled Receptor


Activity: Pathways with Friends

Instructions

1. Form groups of 6 people each

2. Create space for your group to interact without bumping into each other

3. Rules:

Each person in the group will get a card

Do not let others in your group know what your card says

When prompted, follow the instructions on the card


Activity: Pathways with Friends

The Functioning of a G-Protein-Coupled Receptor

Activity:

Receptors in the Plasma Membrane

Tyrosine-kinase receptors are membrane receptors that attach phosphates to tyrosines

A tyrosine-kinase receptor can trigger multiple signal transduction pathways at once

The Structure and Function of a Tyrosine-Kinase Receptor

The Structure and Function of a Tyrosine-Kinase Receptor

Activity:

A Ligand-Gated Ion-Channel Receptor

Hormone(testosterone)

Receptorprotein

Plasmamembrane

EXTRACELLULARFLUID

DNA

NUCLEUS

CYTOPLASM

Steroid Hormone Interacting with an Intracellular Receptor

Receptorprotein


EXTRACELLULARFLUID

Plasmamembrane

Hormone-receptorcomplex

DNA

NUCLEUS

CYTOPLASM



EXTRACELLULARFLUID

Receptorprotein

Plasmamembrane

Hormone-receptorcomplex

DNA

NUCLEUS

CYTOPLASM


Responses to Other Signals

Innerchamber

Outerchamber

–90 mV

140 mM 5 mM

KCIKCI

K+

Cl–

Potassiumchannel

(a) Membrane selectively permeable to K+ (b) Membrane selectively permeable to Na+

+62 mV

15 mMNaCI

Cl–

150 mMNaCI

Na+

Sodiumchannel

CYTOPLASM

Reception

Plasmamembrane

Cellwall

Phytochromeactivated by light

Light

Transduction

Second messenger produced

cGMPNUCLEUS

1 2

Specific protein

kinase 1 activated


CYTOPLASM

Reception

Plasmamembrane

Cellwall


Light

Transduction


cGMPSpecific protein

kinase 1 activated

NUCLEUS

1 2

Specific protein

kinase 2 activated

Ca2+ channel opened

Ca2+


CYTOPLASM

Reception

Plasmamembrane

Cellwall


Light

Transduction


cGMPSpecific protein

kinase 1 activated

NUCLEUS

1 2

Specific protein

kinase 2 activated

Ca2+ channel opened

Ca2+

Response3

Transcriptionfactor 1

Transcriptionfactor 2

NUCLEUS

Transcription

Translation

De-etiolation(greening)responseproteins

P

P


Signal Transduction Pathways

Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation

Signal Transduction Pathways

Protein phosphatases remove the phosphates from proteins, a process called dephosphorylation

This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off

A Phosphorylation CascadeSignaling molecule

ReceptorActivated relaymolecule



Inactiveprotein kinase

1 Activeproteinkinase

1





1


2

ATPADP Active

proteinkinase

2

P

PPP

i





1


2

ATPADP Active

proteinkinase

2

P

PPP


3

ATPADP Active

proteinkinase

3

P

PPP

i

i





1


2

ATPADP Active

proteinkinase

2

P

PPP


3

ATPADP Active

proteinkinase

3

P

PPP

i

ATPADP P

ActiveproteinPP

P i

Inactiveprotein

Cellularresponse

Phosphorylation cascade

i

Second Messengers

The extracellular signal molecule that binds to the receptor is a pathway’s first messenger

Second messengers are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion

Second Messengers

Cyclic AMP (cAMP) is one of the most widely used second messengers

Adenylyl cyclase, an enzyme in the plasma membrane, converts ATP to cAMP in response to an extracellular signal

cAMP as a Second Messenger

First messenger

G protein

Adenylylcyclase

GTP

ATP

cAMPSecondmessenger

Proteinkinase A

G protein-coupledreceptor

Cellular responses

Epinephrine Transduction Pathway

cAMPSecond

messenger

Adenylylcyclase


ATP

GTP

G protein

Epinephrine

cAMPSecond

messenger

Adenylylcyclase


ATP

GTP

G protein

Epinephrine

Inhibition ofglycogen synthesis

Promotion ofglycogen breakdown

Proteinkinase A

Epinephrine Transduction Pathway

cAMP as a Second Messenger

Activity:

Calcium Ions

Calcium ions (Ca2+) act as a second messenger in many pathways

Calcium is an important second messenger because cells can regulate its concentration

The Maintenance of Calcium Ion Concentrationsin an Animal Cell

High Ca++

Low Ca++

Inositol Triphosphate

Pathways leading to the release of calcium involve inositol triphosphate (IP3) and diacylglycerol (DAG) as additional second messengers

Calcium and Inositol Triphosphate in Signaling Pathways

EXTRA-CELLULARFLUID

G protein

GTP

Phospholipase C PIP2

DAG

Endoplasmicreticulum (ER) Ca2+

CYTOSOL

Signaling molecule(first messenger)

IP3

IP3-gatedcalcium channel

(second messenger)



G protein

PIP2

EXTRA-CELLULARFLUID


GTP

IP3

DAG



CYTOSOL

Phospholipase C

(second messenger)

Ca2+

(secondmessenger)



DAG

Variousproteinsactivated

Cellularresponses

Ca2+

(secondmessenger)


CYTOSOL


PIP2

IP3

(second messenger)

GTP

G protein


EXTRA-CELLULARFLUID


Phospholipase C

Nuclear Response to a Signal: The Activation of a

Specific Gene by a Growth Factor

Growth factor

Receptor

Phosphorylationcascade

Reception

Transduction

Activetranscriptionfactor

ResponseP

Inactivetranscriptionfactor

CYTOPLASM

DNA

NUCLEUS mRNA

Gene

Signal Amplification: Stimulation of Glycogen Breakdown by Epinephrine

Is Signal Transduction Important?

Androgen Insensitivity Syndrome:

Genetic male (XY) without androgen receptors

The gene for the syndrome is on the X chromosome in band Xq11-q12.

The gene codes for the androgen receptor.

Result: No signal transduction!

Cell Communication Free-Response Questions

19922. Biological recognition is important in many processes at the molecular, cellular, tissue, and organismal levels. Select three of the following, and for each of the three that you have chosen, explain how the process of recognition occurs and give an example.

a) Organisms recognize others as members of their own species.

b) Neurotransmitters are recognized in the synapse.

c) Antigens trigger antibody responses.

d) Nucleic acids are complementary.

e) Target cells respond to specific hormone


19992. Communication occurs among the cells in a multicellular organism. Choose THREE of the following examples of cell-to-cell communication, and for each example, describe the communication that occurs and the types of responses that result from this communication.

a) Communication between two plant cells

b) Communication between two immune-system cells

c) Communication either between a neuron and another neuron, or between a neuron and a muscle cell

d) Communication between a specific endocrine-gland cell and its target cell


20071. Membranes are essential components of all cells.

a) Identify THREE macromolecules that are components of the plasma membrane in a eukaryotic cell and discuss the structure and function of each.

b) Explain how membranes participate in THREE of the following biological processes:

• Muscle contraction

• Fertilization of an egg

• Chemiosmotic production of ATP

• Intercellular signaling


20081. The physical structure of a protein often reflects and affects its function.

a) Describe THREE types of chemical bonds/interactions found in proteins. For each type, describe its role in determining protein structure.

b) Discuss how the structure of a protein affects the function of TWO of the following.

• Muscle contraction

• Regulation of enzyme activity

• Cell signaling

c) Abnormal hemoglobin is the identifying characteristic of sickle cell anemia. Explain the genetic basis of the abnormal hemoglobin. Explain why the sickle cell allele is selected for in certain areas of the world.

john girard project opening doors. chemical “messengers” cells communicate by chemical...

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