Cell to Cell Communication

Ch.11 – Cell Communication Ch. 45 – Endocrine SystemCh. 43 – Immune SystemCh. 48 - Nervous System

Goals: “I can …” Understand why cells communicate in

multicellular organisms Aknowledge that even unicellular bacteria “share

information” Understand the methods cells use to

communicate Give specific examples of cell communication

related to various systems of the body (endocrine, nervous and immune)

Communication Cells must be able to move materials (Na+, H2O,

O2) across space (cytoplasm) and membranes (within, in/out and between cells)

Cells must be able to move information (DNA &RNA) across space (cytoplasm) and membranes (within, in/out and between cells)

Cells must be able to move messages (enzymes,

hormones, neurotransmitters, antigens, etc) across space (cytoplasm and synapses) and membranes (within, in/out and between cells)

MANDATORY in multicelluar organisms

Forms of Communication Communication between cells can be

Physical Touch Light

Chemical (enzymes, hormones, antigens, antibodies and fertilization)

Signal / reaction Concentration Recognition

Electrical (nerve impulses) Polarization

Most change permeability of a membrane

Review of ProteinsPROTEIN FUNCTION

Contractile; actin, myosin Cytoskeleton fibers and filaments that contract and thus pull on CM; change shape and/or move cell

Messenger; adenaline Cause changes in permeability that allow nerve to fire

Regulatory/hormonal; insulin Regulate whether or not a reaction is on/off or a compound is being made

Structural; collagen Used to build and/or anchor

Storage; albumin, casein Supply amino acids to an infant plant or animal

Defense; antigen, antibody Recognize self and defend against abnormal and nonself

Reactions; lytic enzyme Catalyze a chemical reaction

Transport; hemoglobin Bind to and then transport substances throughout the body

Carrier; membrane pumps Move substances across CM as needed

Review of Plasma Membrane; pg 128

Membrane Transport Proteins; pg 129 and 135

Integral (transmembrane) proteins Channel proteins

Channel or tunnel through which molecules can pass, passive

Carrier proteins Alternates between 2 shapes and moving solutes, passive

Ion pumps Active transport, shape change,

Enzymatic Signal transduction Cell to cell recognition

Review of Junctions Tight junction: cells are tight together and bound by

proteins – keep skin waterproof Gap junction: cytoplasmic channels between cells,

membrane proteins surround a pore – molecules can pass

Desmosomes: function like rivets, keratin proteins

Plasmodesmata / Plants – channels in cell walls that allow cytosol to move from cell to cell. Water and small molecules are continuous.

Fig. 11-4 Plasma membranes

Gap junctionsbetween animal cells

(a) Cell junctions

Plasmodesmatabetween plant cells

(b) Cell-cell recognition

Animal Cells: Gap Junctions

Plant cells: Plasmodesmata

Cell to Cell Recognition

11.1 Signal Transduction Pathways Process by which a signal on a cell’s

surface is converted to a specific cellular response through a series of steps Reception Transduction Response

Long distance vs Local Local

Influence cells in the vicinity Growth factors Synaptic signaling Many cells can respond

Long distance Signals are released by specialized cells and travel

through the system, only being recognized by target cells – hormones and pheromones

Electrical portion of nerve impulses Specificity

3 steps in signaling Reception – target cell’s detection of a signal molecule

coming from outside and binding to receptor protein on the cells surface

Transduction – bonding changes receptor protein in some way, initiating transduction, start of pathway – may be protein construction or enzymatic reaction

Response - triggering of a specific cellular response,

Right time, right place, right amount, right sequence, right conditions, etc

Fig. 11-7b

G protein-coupledreceptor

Plasmamembrane

EnzymeG protein(inactive)

GDP

CYTOPLASM

Activatedenzyme

GTP

Cellular response

GDP

P i

Activatedreceptor

GDP GTP

Signaling moleculeInactiveenzyme

1 2

3 4

G Protein Coupled Receptors pg 211

Fig. 11-7c

Signalingmolecule (ligand)

Ligand-binding site

Helix

TyrosinesTyr

Tyr

Tyr

Tyr

Tyr

Tyr

Receptor tyrosinekinase proteins

CYTOPLASM

Signalingmolecule

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Dimer

Activated relayproteins

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

P

P

P

P

P

P

Cellularresponse 1

Cellularresponse 2

Inactiverelay proteins

Activated tyrosinekinase regions

Fully activated receptortyrosine kinase

6 6 ADPATP

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

Tyr

P

P

P

P

P

P

1 2

3 4

Receptor Tyrosine Kinases pg 212

Fig. 11-7d

Signalingmolecule(ligand)

Gateclosed Ions

Ligand-gatedion channel receptor

Plasmamembrane

Gate open

Cellularresponse

Gate closed3

2

1

Ion Channel ReceptorsPg 213

11.2 Reception Ligand – molecule that has specific binding affinity to another

molecule. Causes a shape change – directly activates receptor to interact with another molecule

Receptors in Plasma membrane G Protein Coupled Receptors Tyrosine receptor kinases Ion channel receptors

Intracellular Receptors - hydrophobic or small to pass through CM (steroids, thyroid hormones and NO) Only target cells have correct receptors In cytoplasm In nucleus – transcription factors; control which genes are “on”

11.3 Transduction Pathways: chain of molecular events, usually involve removal of

PO4, signal molecule usually never enters cell

Cascades: series of molecules in pathway are phosphorylated in turn, “fan out”

Phosphorylation / dephosphorylation: Protein kinase is enzyme that transfers P from ATP to a protein. 2% of genes code for kinases ! Protein phosphatases are enzymes that remove P – inactivating protein

Second messengers: small, nonprotein, water soluble molecules or ions, spread rapidly by diffusion, cyclic AMP and Ca+2

Cyclic AMP and Calcium

11.4 Response Regulation of one or more cell activities

Regulation of protein synthesis ( genes on/off) Regulation of activity of a protein Open or shut a gate or channel

In cytoplasm and/or nucleus Liver cell and cardiac muscle cells both respond to

epinephrine – liver breaks down glycogen and heart beats more rapidly….

Different kinds of cells have different collections of proteins.

Programmed cell death: Apoptosis

Endocrine system

Communication examples from endocrine system

Nervous system

Communication examples from nervous system

Immune system

Communication examples from immune system

Learner Outcomes Read a scientific article and relate ideas to

concept of cell communication. See links between chemistry and membrane structure

Have a basic understanding of the immune, endocrine and nervous systems.

Practice Essay Questions Previous AP Exam question (2010)

1. Homeostatic maintenance of optimal blood glucose levels had been intensively studied in vertebrate organisms.

A. Pancreatic hormones regulate blood glucose levels. Identify TWO pancreatic hormones and describe the effect of each hormone on blood glucose levels.

B. For ONE of the hormones you identified in A.) identify ONE target cell and discuss the mechanism by which the hormone can alter activity in the target. Include in your discussion a description of cellular reception, transduction and response.

Compare the cell-signaling mechanisms of steroid hormones and protein hormones

Pg. 227 in Campbell and Reece 8th ed. Scientific Inquiry # 11 Science Technology and Society # 12