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Cell to Cell
Communication
Ch.11 – Cell Communication
Ch. 45 – Endocrine System
Ch. 43 – Immune System
Ch. 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
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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
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Communication between cells can be
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Physical
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Chemical (enzymes, hormones, antigens, antibodies and
fertilization)
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Signal / reaction
Concentration
Recognition
Electrical (nerve impulses)
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Touch
Light
Polarization
Most change permeability of a membrane
Review of Proteins
PROTEIN
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
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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 junctions
Animal
Cells:
between
animal cells
Gap Junctions
(a) Cell junctions
Plasmodesmata
Plant
cells:
between
plant cells
Plasmodesmata
Cell to Cell Recognition
(b) Cell-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
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Reception
Transduction
Response
Long distance vs Local

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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
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Electrical portion of nerve impulses
Specificity
3 steps in signaling
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Reception – target cell’s detection of a signal molecule
coming from outside and binding to receptor protein on the cells
surface
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Transduction – bonding changes receptor protein in some
way, initiating transduction, start of pathway – may be protein
construction or enzymatic reaction
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Response - triggering of a specific cellular response,
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Right time, right place, right amount, right sequence, right
conditions, etc
Fig. 11-7b
G Protein Coupled Receptors pg 211
Plasma
membrane
G protein-coupled
receptor
Activated
receptor
Signaling molecule
GDP
CYTOPLASM
GDP
Enzyme
G protein
(inactive)
GTP
2
1
Activated
enzyme
GTP
GDP
Pi
Cellular response
3
4
Inactive
enzyme
Fig. 11-7c
Receptor
Tyrosine Kinases pg 212
Ligand-binding site
Signaling
molecule (ligand)
Signaling
molecule
 Helix
Tyrosines
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Receptor tyrosine
kinase proteins
CYTOPLASM
Dimer
1
2
Activated relay
proteins
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
P Tyr
P Tyr
6 ATP
Activated tyrosine
kinase regions
6 ADP
P Tyr
Tyr
P
Tyr P
Tyr P
P Tyr
Tyr
P
P Tyr
P Tyr
Tyr
P
P
Tyr
Fully activated receptor
tyrosine kinase
Inactive
relay proteins
3
4
Cellular
response 1
Cellular
response 2
Fig. 11-7d
1 Signaling
molecule
(ligand)
Gate
closed
Ions
Ion Channel
Receptors
Pg 213
Ligand-gated
ion channel receptor
Plasma
membrane
2 Gate open
Cellular
response
3
Gate closed
11.2 Reception
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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
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Pathways: chain of molecular events, usually involve removal of
PO4, signal molecule usually never enters cell
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Cascades: series of molecules in pathway are phosphorylated in
turn, “fan out”
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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
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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
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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
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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
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Previous AP Exam question (2010)
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1. Homeostatic maintenance of optimal blood glucose levels had been
intensively studied in vertebrate organisms.
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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.
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Scientific Inquiry # 11
Science Technology and Society # 12