Lecture+13+-+Nutrition+and+Energy+Metabolism+I (4)

Lecture+13+-+Nutrition+and+Energy+Metabolism+I (4) -...

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Unformatted text preview: Wednesday’s Class: NUTRIENTS & ENERGY METABOLISM 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 kineXc and potenXal 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 duraXon and efficiency of a parXcular pathway. •  Discuss why heat is produced when energy is used. Energy •  Energy – ability to do work •  Energe'cs – energy transfer between systems •  Types of energy –  Poten'al – trapped energy –  Kine'c – energy of movement Categories of Energy •  Heat –  Radiant energy – transmi^ed from one object to another –  Thermal energy – movement of molecules •  Also called molecular kineXc energy •  Mechanical energy – movement of objects •  Electrical energy – movement of charged parXcles down a charge gradient •  Chemical energy – within chemical bonds Animals rely on all five types of energy, which are interconverXble. 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 sXck. 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… ReacXons with enzymes that require oxygen, e.g., ATP producXon •  •  •  •  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 Xon Oxi d a Rege neraX 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 PhosphorylaXon: ATP synthesis ATP Synthase Proton moXve force generated by proton gradient is a source of potenXal 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 producXon for Short DuraXon –  CreaXne phosphate (vertebrates), Arginine phosphate (invertebrates) –  Fast EnzymaXc replenishment: CreaXne Kinase •  CK acXvity limits burst performance potenXal •  Anaerobic Glycolysis –  Fast ATP producXon for Moderate DuraXon –  Glucose, glycogen supply in muscle –  Energy Inefficient •  OxidaXve using O2 in environment –  Slow ATP producXon for Long DuraXon –  Energy Efficient Animals use energy to perform 3 major funcXons TransformaXon of high-­‐grade energy is inefficient Efficiency of energy transformaXon = 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 moXon = ~25-­‐30% Metabolism “The set of processes by which cells and organisms acquire, rearrange and void commodiXes in ways that sustain life” (Hill, Wyse & Anderson) “The sum of all chemical reacXons in a biologic enXty” (Moyes & Schulte) Metabolic Rate “An [organism’s] rate of energy consumpXon; the rate at which it converts chemical-­‐bond energy to heat and external work” (Hill, Wyse & Anderson) Metabolic Rate Principles in Animal Physiology Metabolic rates are significant because: •  Determinant of how much food an animal needs •  QuanXtaXve measure of the total acXvity of all its physiological mechanisms •  Measurement of the drain the animal places on the energy supplies of an ecosystem/ agricultural system What goes into metabolic rate? 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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