Cell to Cell Communication

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

2. 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)

3. 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

4. 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

5. Review of Proteins

6. Review of Plasma Membrane; pg 128

7. 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

8. 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.

9. Fig. 11-4 Plasma membranes Animal Cells: Gap Junctions Gap junctions between animal cells Plant cells: Plasmodesmata Plasmodesmata between plant cells (a) Cell junctions Cell to Cell Recognition (b) Cell-cell recognition

10. 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

11. 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

12. 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

13. G Protein Coupled Receptors pg 211 Fig. 11-7b Plasma membrane Inactive enzyme G protein-coupled receptor Signaling molecule Activated receptor GDP GTP GDP Enzyme G protein (inactive) CYTOPLASM 2 1 Activated enzyme GTP GDP P i Cellular response 4 3

14. Receptor Tyrosine Kinases pg 212 Ligand-binding site Signaling molecule (ligand) Signaling molecule Fig. 11-7c  Helix Tyr Tyr Tyr Tyr Tyr Tyr Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Receptor tyrosine kinase proteins Dimer CYTOPLASM 1 2 Activated relay proteins Cellular response 1 P P Tyr Tyr P Tyr Tyr Tyr Tyr P Tyr P Tyr P P Tyr Tyr Tyr Tyr P Cellular response 2 P P Tyr Tyr P Tyr Tyr Tyr Tyr P 6 ATP 6 ADP Activated tyrosine kinase regions Fully activated receptor tyrosine kinase Inactive relay proteins 4 3

15. Fig. 11-7d 1 Signaling molecule (ligand) Gate closed Ions Ion Channel Receptors Pg 213 Plasma membrane Ligand-gated ion channel receptor 2 Gate open Cellular response 3 Gate closed

16. 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”

17. 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

18. Cyclic AMP and Calcium

19. 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.

20. Programmed cell death: Apoptosis

21. Endocrine system

22. Communication examples from endocrine system

23. Nervous system

24. Communication examples from nervous system

25. Immune system

26. Communication examples from immune system

27. 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.

28. 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