Chapter 8 Lecture Notes on Cell Communication PDF

Chapter 8: How cells communicate with each other Nom, nom, nom. Me hungry!! https://www.youtube.com/watch?v=I_xh-bkiv_c “Cell Surface Receptors” bind messenger-like molecules that circulate outside the cell. These molecules tell the cell it needs to respond. Most receptors can be...

Chapter 8: How cells communicate with each other Nom, nom, nom. Me hungry!! https://www.youtube.com/watch?v=I_xh-bkiv_c “Cell Surface Receptors” bind messenger-like molecules that circulate outside the cell. These molecules tell the cell it needs to respond. Most receptors can be classified as either Enzyme-linked receptors G-protein-coupled receptors O J Ligand-gated ion channels of O · o Bacteria shed polysaccharides, which are signaling molecules that bind to receptors on the neutrophil. YY Y Y Loading… YY Y Y https://www.youtube.com/watch?v=I_xh-bkiv_c Cell signaling connects to concepts we’ve studied already. polar Q Example 1: Import of Glucose into a cell for cellular respiration. Signaling Example 1: How does the glucose get into the cell for Cellular Respiration to extract its energy to make ATP? Glucose is polar and cannot diffuse through the cell membrane Loading… Signaling Example 1: How does the glucose get into the cell for Cellular Respiration to extract its energy to make ATP? Step 1. Pancreatic cells make and secrete insulin when you eat. Signaling Example 1: How does the glucose get into the cell for Cellular Respiration to extract its energy to make ATP? Step 2. Insulin binds to receptors extending from the cell’s surface and “signals” the cell to let glucose in Enzyme –linked receptors Signaling Example 2: What signaling occurs in the stress response? Epinephrine is released to “signal” the cleavage of monosaccharides from glycogen. The monosaccharide (glucose) are used to make ATP for flight or fight response. G Protein coupled receptors Signaling Example 2: What signaling occurs in the stress response? How is muscle action in the stress response increased? Ligand gated Ion channels  Most receptors can be classified as either Enzyme-linked receptors G-protein-coupled receptors Ligand-gated ion channels Signaling Example 2: What signaling occurs in the stress response? Other ways that cells get more glucose…by Cortisol signaling. Loading… Nonpolar ligands diffuse through the membrane to reach Intracellular receptors Summary of Stress response Insulin binds to ___________________ enzyme-linked to tell the cell to let glucose receptors in (for ATP production) Epinephrine binds to ___________________to signal an enzyme to G - Protein coupled receptors cleave glucose monosaccharides from glycogen (for more ATP production) Cortisol binds to ___________________to intercellular receptors. stimulate the conversion of amino acids to glucose (for even more ATP production) Neurons “tell” muscle cells to increase rate of contraction (and hence use of all that ATP) when neurotransmitters from the neuron bind to ___________________on ligand-gated ion channels the muscle cell and let ions diffuse in.  Chapter 8 How Cells Communicate with Each Other and with the Environment 8.1 General Features of Cell Communication Section 8.1 Learning Outcomes 1. List 2 general reasons cells need to respond to signals 2. Compare and contrast the 5 ways that cells communicate with each other based on the distance between them 3. Outline the 3-stage process of cell signaling 8.1 General Features of Cell Communication All living organisms (bacteria, archaea, protists, fungi, plants, and animals) require cell communication to survive Cell communication (aka cell signaling) involves both Responding to incoming signals and Producing outgoing signals Signals are often chemical molecules Signals can also be physical parameters like light or temperature  8.1 General Features of Cell Communication Cells Detect and Respond to Signals from Their Environment and from Other Cells Why is cell communication necessary?. To respond to a changing environment a cellular response to the environment can be critical for survival. To communicate with each other critical for multicellular organisms 8.1 General Features of Cell Communication Cell-to-Cell Communication Occurs Between Adjacent Cells and Between Cells That Are Long Distances Apart 8.1 General Features of Cell Communication Cells Usually Respond to Signals via a 3-Stage Process Three common stages of cell signaling are receptor activation, signal transduction, and cellular response Often, a group of proteins form a signal transduction pathway 8.2 Receptor Activation Section 8.2 Learning Outcomes 1. Explain how a signaling molecule, or ligand, binds to its receptor and causes a conformational change that activates the receptor 2. Interpret the affinity, measured as a dissociation constant, that a receptor has for its signaling molecule, or ligand 8.2 Receptor Activation Receptors Bind to Specific Signals and Undergo signalingeeConformational Changes A ligand (signaling molecule) binds noncovalently to its receptor with high specificity Ligand binding changes the receptor structure; this conformational change transmits the signal across the membrane Once the ligand is released, the receptor reverts to the inactive conformation 8.2 Receptor Activation Receptors Bind to Specific Signals and Undergo Conformational Changes Once the ligand is high affinity ligands released, the low affinity ligands receptor reverts to the inactive conformation 8.2 Receptor Activation Receptors Have a Measureable Affinity for Their Ligands The complex that forms between the ligand and its receptor is stable -o for a finite period of time; the complex will dissociate kon [Ligand] + [Receptor] [Ligand-Receptor complex] Doninave O koff to know for 140 kon is the rate at which binding occurs koff is the rate at which the ligand-receptor complex dissociates Kd, the dissociation constant, is used to quantify the affinity receptors have for their ligands At equilibrium, Kd = koff / kon 8.2 Receptor Activation How much ligand is needed to get the cell to respond? *Cells respond when 50% of receptors for that ligand are bound to ligand* This amount of ligand called Kd. Kd is different for different cell types and/or different receptor types. Kd is the concentration of ligand needed to bind to 50% of receptor. Kd can also be considered the “minimum effective dose” of ligand needed to get a cell to respond to its presence. ⑨ ↳ = * hd needed : In ⑧ num s cardiomyocyte neuron = Do & & 8 P Pancreatic We. & & beta cell O. & -199 8.2 Receptor Activation What is the yellow receptor Kd for these 3 cell types? Which cell will respond to presence of the ligand at the smallest concentration of ligand? cardiomyocyte neuron Pancreatic beta cell 8.2 Receptor Activation What is the yellow receptor Kd for these 2cell types? Which cell will respond to presence of the ligand at the smallest concentration of ligand? If the actual [ligand] is 3, will either cell respond? If the actual [ligand] is 5, will either cell respond? If the actual [ligand[ is 9, will either cell respond? Pancreatic cardiomyocyte beta cell 8.2 Receptor Activation What is the yellow receptor Kd for these 2 cell types? Which cell will respond to presence of the ligand at the smallest concentration of ligand? If the actual [ligand] is 3, will either cell respond? If the actual [ligand] is 5, will either cell respond? If the actual [ligand[ is 9, will either cell respond? Pancreatic cardiomyocyte beta cell If [ligand] is _ Kd Cell response? < no = yes > yes 8.3 Cell Surface Receptors Section 8.3 Learning Outcomes 1. Compare and contrast the 3 general types of cell surface receptors 8.3 Cell Surface Receptors Most signaling molecules are small and hydrophilic or too large to pass through the plasma membrane Cell surface receptors that are embedded in the plasma membrane detect these types of extracellular signals An individual cell may have hundreds of different cell surface receptors This way the molecule doesn’t even need to enter the cell It’s presence just needs to be relayed into the cell by a receptor it can bind to 8.3 Cell Surface Receptors Most receptors can be classified as either Enzyme-linked receptors G-protein-coupled receptors Ligand-gated ion channels Loading… 8.3 Cell Surface Receptors Enzyme-linked receptors typically have 2 important domains: an extracellular signal-binding domain and an intracellular catalytic domain Most enzyme-linked receptors function as https://www.you protein kinases; they tube.com/watch transfer a phosphate ? group from ATP to a v=MMS4l7cSB specific amino acid in DU target proteins Phosphorylation alters the structure and function of a protein  https://www.youtube.com/watch? 8.3 Cell Surface Receptors v=Glu_T6DQuLU&t=76s G-proteins-coupled receptors (GPCRs) interact with intracellular proteins called G proteins; G proteins can bind GTP and GDP Receptor activation causes the α subunit and β/γ dimer of the G protein to dissociate subunits interact with other proteins 8.3 Cell Surface Receptors When a signaling molecule binds a ligand-gated ion channel, the channel opens and allows the flow of ions across the membrane 8.4 Intracellular Receptors Section 8.4 Learning Outcomes 1. Describe intracellular receptors, using the estrogen receptor as an example 8.4 Intracellular Receptors Intracellular receptors, found in the cytosol or nucleus, bind signal molecules that are small and hydrophobic Such signals can diffuse across the plasma membrane Activation of an intracellular receptor typically leads to a change in gene expression Steroid hormones like estrogen and testosterone utilize intracellular receptors