Lecture+12+-+Cell+Signaling+%233+%26+Nutrition+and+Energy+Metabolism+I (6) (1)

Lecture+12+-+Cell+Signaling+%233+%26+Nutrition+and+Energy+Metabolism+I (6) (1)

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Unformatted text preview: Tuesday’s Class: RECEPTORS & CELL SIGNALING #3 Chapter 4 Pages: 98-­‐130 Chapter 3 Pages: 90-­‐121 Midterm Exam #1: Tuesday April 19st In Class (10:00 – 10:50AM) Worth 20% of Final Grade MulTple Choice, Matching & Short Answer Covers all lecture material up to and including Friday April 15th. Assigned reading from textbook is meant to compliment lectures. I will not test you on secTons of a parTcular chapter assigned from the textbook that we did not cover in lecture. IntroducTon to Physiological Systems Animals & Their Environment Molecular & Cellular Physiology BRING UCD 2000 scantron Transport of Solutes & Water Receptors & Cell Signaling NutriTon, Energy Metabolism & Metabolic Rate Important Deadlines Problem Set #1 – Available 5PM Tuesday April 5th •  Closes Tuesday April 12th, 11:59PM •  ONE SUBMISSION ONLY (save and don’t submit unTl ready) •  Answers will only be revealed a`er quiz closes •  4% of total grade •  BE SURE TO SUBMIT YOUR ANSWERS BY DEADLINE! What you should be able to do by the end of today’s lecture •  Compare the main classes of receptors and provide examples of situaTons where the receptors regulate physiological processes. •  Describe the diversity in receptor-­‐enzymes and enzyme-­‐linked receptors, and recognize the importance of protein kinase and protein phosphatases. •  Discuss how G-­‐protein linked receptors induce downstream responses. Ligand-­‐Receptor Binding •  L + R ↔ L-­‐R à response –  FormaTon of L-­‐R complex causes response –  More free ligand (L) or receptors (R) will increase the response •  Law of mass acTon •  Receptors can become saturated at high L –  Response is maximal Receptor number & affinity can vary •  More receptors = more likely ligand will bind at any given ligand concentraTon •  Can upregulate (e.g. caffeine) and downregulate (e.g. heroin) receptor numbers •  Receptors can vary in the strength with which they bind ligand InacTvaTon of Ligand-­‐Receptor Complex •  L-­‐R complex must be inacTvated to allow responses to changing condiTons Principles of Animal Physiology Figure 4.16 Signal TransducTon Pathways •  Convert signals from one form to another •  Four components –  Receiver: ligand binding receptor –  Transducer: conformaTonal change of the receptor –  Amplifier: the signal transducTon pathway increases the number of molecules affected –  Responder: something that responds to the signal Types of Receptors (hydrophobic vs. philic messengers?) Focus on signal transducTon pathways most important in regulaTng physiological processes Principles of Animal Physiology Figure 4.18 Intracellular Receptors •  Ligand diffuses across cell membrane •  Binds to receptor in cytoplasm or nucleus •  L-­‐R complex binds to specific DNA sequences •  Regulates the transcrip4on of target genes •  increases or decreases producTon of specific mRNA Principles of Animal Physiology Figure 4.19 Changes in gene transcripTon Types of Receptors (hydrophobic vs. philic messengers?) Focus on signal transducTon pathways most important in regulaTng physiological processes Principles of Animal Physiology Figure 4.18 Ligand-­‐Gated Ion Channels Ligand binds to receptor Receptor changes shape opening a channel Ions move across the membrane ConcentraTon and electrical gradients dictate the direcTon of ion movement •  Movement of ions change ion concentraTons which alters the membrane potenTal Principles of Animal Physiology Figure 4.21 •  •  •  •  Receptor Enzymes (also called enzyme/enzyme-­‐linked receptors) •  When acTvated by a ligand the catalyTc domain starts a phosphoryla4on cascade •  Named based on the reacTon catalyzed Principles of Animal Physiology Figure 4.22 G-­‐Protein-­‐Coupled Receptors •  Transmembrane protein that interacts with intracellular G-­‐proteins •  G-­‐proteins – named for their ability to bind guanosine nucleoTdes •  AcTvate second messengers Principles of Animal Physiology Figure 4.27 Cyclic AMP Signaling (First intracellular 2nd messenger discovered) Principles of Animal Physiology Figure 3.27 Tuesday’s Class?: NUTRIENTS & ENERGY METABOLISM *most will be covered on Wednesday Chapter 2 Pages: 39-­‐44, 71-­‐74 Chapter 2 Pages: 22-­‐27, 57-­‐60 What you should be able to do by the end of today’s lecture •  Explain the different categories of energy. Understand the differences between kineTc and potenTal energy and give examples of each. •  Understand how energy is stored in the body and how ATP is produced in the mitochondria when oxygen is available. •  Explain the four main pathways that supply ATP and the duraTon and efficiency of a parTcular pathway. •  Discuss why heat is produced when energy is used. Energy •  Energy – ability to do work •  Energe4cs – energy transfer between systems •  Types of energy –  Poten4al – trapped energy –  Kine4c – energy of movement Categories of Energy •  Heat –  Radiant energy – transmined from one object to another –  Thermal energy – movement of molecules •  Also called molecular kineTc energy •  Mechanical energy – movement of objects •  Electrical energy – movement of charged parTcles down a charge gradient •  Chemical energy – within chemical bonds Animals rely on all five types of energy, which are interconverTble. Chemical Bonds •  Most biologically available energy is stored in chemical bonds Two main types of bonds •  Covalent bonds (strong bonds) – individual atoms held together by the sharing of electrons •  Noncovalent bonds (weak bonds) – molecules organized into three-­‐ dimensional structures van der Waals in nature: How geckos sTck. Energy Storage Cells store energy in two main forms •  Reducing energy •  High energy bonds Energy can be “stored” in covalent bonds •  Energy is released when bonds are broken •  ATP is the most common “high energy” molecule In most animals and plants, Energy is not stored as ATP •  Lipids •  Carbohydrates –  Starch (plants) –  Fructans (plants) –  Glycogen (animals) –  Trehalose (insects) –  Sucrose (plants) •  Proteins & Amino Acids Chemical Poten.al Energy! Food goes in… ReacTons with enzymes that require oxygen, e.g., ATP producTon •  •  •  •  Cytoplasmic enzymes convert nutrients into metabolites Metabolites are carried to mitochondria Metabolites are further broken down to release energy Many metabolites are converted to acetyl CoA •  Energy in acetyl CoA transferred to NADH and FADH2 Figure 2.38 …Reducing equivalents come out Ton Oxi d a Rege neraT Reducing equivalents come out (passed on to ETC to make ATP) on Acetyl CoA goes in CO2 out Acetyl CoA is oxidized to reducing equivalents (NADH & FADH2) Principles of Animal Physiology, Figure 2.39 Mitochondrial Electron Transport Chain builds an electrochemical gradient that can be used to drive ATP synthesis Figure 2.40 Mitochondrial Electron Transport Chain Protons pumped into intermembrane space And Cytochrome C Electrons transferred via Ubiquinone Reducing poten.al from TCA cycle Electrons finally accepted by Oxygen Figure 2.40 Mitochondrial Electron Transport Chain PhosphorylaTon: ATP synthesis ATP Synthase Proton moTve force generated by proton gradient is a source of potenTal energy that drives ATP synthesis M&S Figure 2.40 2.40 ATP Supply Routes •  Free ATP –  Instant, only a few seconds •  Phosphagen –  Very Fast ATP producTon for Short DuraTon –  CreaTne phosphate (vertebrates), Arginine phosphate (invertebrates) –  Fast EnzymaTc replenishment: CreaTne Kinase •  CK acTvity limits burst performance potenTal •  Anaerobic Glycolysis –  Fast ATP producTon for Moderate DuraTon –  Glucose, glycogen supply in muscle –  Energy Inefficient •  OxidaTve using O2 in environment –  Slow ATP producTon for Long DuraTon –  Energy Efficient Animals use energy to perform 3 major funcTons TransformaTon of high-­‐grade energy is inefficient Efficiency of energy transformaTon = Output of high-­‐grade energy Input of high-­‐grade energy Conversion of chemical bond energy in a fuel molecule (e.g. glucose) to chemical bond energy of ATP Glucose to ATP = ~70% (rest “lost” as heat) ATP to muscular moTon = ~25-­‐30% Next Class METABOLISM & METABOLIC RATE Chapter 1: pages 9-­‐11 Chapter 14: pages 628-­‐631 Chapter 2 Box 2.2 Chapter 11: pp 529-­‐530 ...
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