Cellular Communication
But before we get into that What have we learned about so far? Energy and Matter Why do living things need energy? Grow Reproduce Maintain homeostasis
Cellular signaling Cells communicate with each other How? Molecules! Why do cells communicate with each other?
Cellular signaling Ways that cells communicate Direct Contact Junctions and Cell to cell contact Short distances Proteins Long Distances Hormones
Here s how to start You will be researching 3 topics Cell to cell contact Cell to cell recognition Not junctions we already did that Local signaling Paracrine and synaptic signaling Long distance signaling Hormone signaling
Your assignment Use the Chromebooksto research these 3 topics. For each topic highlighted in red Write a short summary about what you learned Give an example of an actual use of this signaling in animals/humans (and for the hormone one, give an example in plants too) Have fun and learn lots!
5 th hour this is you! Ok everybody, today you will be going through this powerpointat your own pace. Some slides ask you to open a book and read please do that as you move forward. The pictures on the next 3 slides show the examples of the types of signaling you looked up yesterday.
Plasma membranes Gap junctions between animal cells Plasmodesmata between plant cells (a) Cell junctions (b) Cell-cell recognition
Local signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter. Secreting cell Secretory vesicle Neurotransmitter diffuses across synapse. Local regulator diffuses through extracellular fluid. (a) Paracrine signaling (b) Synaptic signaling Target cell is stimulated.
Long-distance signaling Endocrine cell Blood vessel Hormone travels in bloodstream. Target cell specifically binds hormone. (c) Endocrine (hormonal) signaling
Here s the important part of this Cellular communication is related to gene expression How? Well, each cell has its own DNA which is used to control its own function. Big question: Can one cell regulate the DNA use of another cell?
You are about to find out!
How does cellular communication work? A cell has 3 stages of receiving and responding to a signal Reception Transduction Response
Step 1: Reception Cellular messages are only heard by those cells that need to receive the message Signal molecules bind to specific protein receptors Like enzymes, only the right one fits Receptor molecule changes shape upon binding
Step 1: Reception Receptors are found in the cytoplasm and the cell membrane Cytoplasm hydrophobic or small receptors Membrane- hydrophilic receptors
Membrane Receptor Types G-protein osine Kinase Ligand-gated ion channel Please check out pages 206-208 in your book to learn how each of these types of receptors work
G protein-coupled receptor Plasma membrane Activated receptor Signaling molecule Inactive enzyme CYTOPLASM 1 GDP G protein (inactive) Enzyme 2 GDP GTP GDP GTP Activated enzyme GTP GDP P i 3 Cellular response 4
Signaling molecule (ligand) αhelix in the membrane Ligand-binding site Signaling molecule osines CYTOPLASM 1 Receptor tyrosine kinase proteins (inactive monomers) 2 Dimer Activated relay proteins 6 ATP 6 ADP Activated tyrosine Fully activated kinase regions receptor tyrosine (unphosphorylated kinase dimer) (phosphorylated 3 dimer) 4 P P P P P P P P P P P P Inactive relay proteins Cellular response 1 Cellular response 2
1 2 3 Signaling molecule (ligand) Gate closed Ions Gate open Gate closed Ligand-gated ion channel receptor Plasma membrane Cellular response
Step 2: Transduction Signal Transduction Pathways The receptor passes the signal along to other molecules Not the signaling molecule but a cascade of activated proteins Results in amplified signal Results in a specialized signal Eventually, this results in an activated protein at the end of the cascade This is important
Signaling molecule Receptor Activated relay molecule Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 P i ATP PP ADP Active protein kinase 2 P Please check out page 209 to get a good feel for what is going on here. Inactive protein kinase 3 P i ATP PP ADP Active protein kinase 3 P Inactive protein ATP PP ADP Active protein P Cellular response P i
Signal Transduction Pathway Important pathway actions Protein phosphorylation performed by protein kinases Kinase = Enzyme capable of phosphorylating another protein Proteins are dephosphorylated by protein phosphatases Phosphatase = kinase deactivator; removes phosphate Shut the cascade down so proteins can be phosphorylated again
Back to our original question Big question: Can one cell regulate the DNA use of another cell? What s the answer?
Back to our original question YES!! One cell can influence another s gene expression As a result of controlling gene expression, one cell can influence another cell s function What does all this mean? Your cells are all working together. Homeostasis can also be maintained through genetics!
Step 3: Response The end result is the cell takes action 2 types of response Cytoplasmic response Regulates the activity of active enzymes Nuclear response Regulate the genes that produce enzymes to either stop producing them or start producing them
Remember these: Key points to gene regulation Sounds like what we just saw on the previous slide! Here is gene regulation in its simplest form (remember this?): 1. Adjust the activity of enzymes that are already there. A.K.A: Inactivate the protein products so it s like the gene is not producing them. 2. Adjust the amount of enzymes being made A.K.A: Prevent the gene from being read so its protein products aren t produced
Example: Cytoplasmic response Regulating an enzyme The action of epinephrine on liver cells influences metabolism Catalyzes the breakdown of glycogen to produce glucose Amplified as it continues
Reception Binding of epinephrine to G protein-coupled receptor (1 molecule) Transduction Inactive G protein Active G protein (10 2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10 2 ) ATP Cyclic AMP (10 4 ) Inactive protein kinase A Active protein kinase A (10 4 ) Inactive phosphorylase kinase Active phosphorylase kinase (10 5 ) Inactive glycogen phosphorylase Active glycogen phosphorylase (10 6 ) Response Glycogen Glucose 1-phosphate (10 8 molecules)
Example: Nuclear Response Well not quite
Example: Nuclear Response Gene regulation Activation of a gene by a growth factor The final product of the signal transduction cascade enters the nucleus and activates a transcription factor!!!! The transcription factor activates as specific gene (We will learn more about this later) Check it out! Gene regulation. One cell produces a product that eventually activates (or deactivates) genes in another cell
Growth factor Receptor Reception Phosphorylation cascade Transduction CYTOPLASM DNA Inactive transcription factor Active transcription factor P Response Gene NUCLEUS mrna
You did it! Now get your lab report done for Monday!