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