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UNC-Chapel Hill BIOC 108 - Unit 1

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Unit 1.1: Overview of MetabolismFunctional Groups:- Hydrocarbons:o Alkanes: saturated C-C bondso Alkenes: unsaturated C=C bonds o Aromatic: contains benzene ringMacromolecules: synthesized through condensation - Proteins: linking amino acid monomers, 20 different monomers- Polynucleotides: (RNA & DNA) linking single nucleotide monomers - Polysaccharides: linking monosaccharides - Lipids: hydrophobic, glycerol and 3 fatty acids (triglycerides)  Phospholipids and cholesterol are also types of lipidsPhospholipids: form lipid bilayers, the basic of all cellular membranes- Hydrophilic heads- Hydrophobic tails - Membranes are selectively permeable (highly polar, large cannot cross)- They contain transport proteins Our bodies are out of equilibriumMetabolic energy to stay alive comes from biological oxidations: - We eat energy-rich (reduced) carbs and lipids, we oxidize them to carbon dioxide for energy to stay alive - The energetic electrons from these oxidations are used to make ATP**When G is negative, products are at lower energy state than reactants = spontaneous**ATP drives thermodynamically unfavorable reactions **ATP stores energy in phosphate bonds Free energy is used for 3 purposes:1. Mechanical work = cellular movements and muscle contraction2. Molecular transport = molecules/ions are actively transported inside cell3. Biosynthesis = synthesizing macro-biomolecules 1.3 – Lipid Chemistry, Structure, & Function, Biological Membranes Lipids: biomolecules that are overall hydrophobic- Very non-polar- Insoluble in water- Soluble in organic (non-polar) solventsFunctions:- Energy source (triglycerides)- Energy stores (adipose tissue triglycerides)- Triglycerides are completely hydrophobic, highly-reduced (energy rich) compact, efficient energy storage, good insulator - Membranes- Signaling molecules - Fat-solubleFatty acids: basic building blocks of most lipids- Structure: long-chain carboxylic acids - Stearic Acid = 18:0 (18C, no double bonds)- Nomenclature: start counting C1 at the carboxylic acid Alpha carbon is next to C1 Beta carbon is next to alpha carbon  Omega carbon is the last carbonExample: CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH18:2618 carbons: 2 double bonds total  first double bond closest to the omega endStructure vs. Melting Point: o The longer the chain, the higher the melting point o The more double bonds, the lower the melting point o Essential = 6 and 3 (required in diet)Physiological Functions of Lipids = A PROBLEM!o Hydrophobicity and fluidity o Length + # of double bonds affect cell membranes and storage of energy (adipose tissue)o The more tightly packed, the more solid they are o We want our fatty acids to be liquids, but their natural property is to be solid at room temperature o We fix this by putting in double bonds o EXAMPLE: Stearic acid = 18:0 (putting just 1 double bond drops melting point below body temp and a fluid state is possible) Saturated = no double bondsTrans fatty acid: contains a double bond, hydrogens on opposite sides of double bondCis fatty acids: contains a double bond, hydrogens are on the same side of double bondKinks = less packing, more fluid = GOOD for membranes Trans fatty acids = no kinks, packed tightly, worse than saturated = BAD for membranesTriglycerides:***Fatty acids can form esterso Most fatty acids in the body are esterified (mostly triglycerides in adipose and phospholipids in membranes) o Alcohol (glycerol) + carboxylic acid (fatty acid) = ester (glyceride)Phospholipids & Membranes:o Phospholipids = vital components of membranes o Glycerol backgroundo 2 FA in ester linkages o Polar head = phosphate + X (EX: choline) attached to glycerolo Hydrophobic tail = the 2 fatty acids Sterols: cholesterol (buried in hydrophobic part of membrane, increases fluidity)  testosterone glycocholate Cell Membrane: consists of lipid bilayer integral proteins are embedded in this lipid bilayer  Sugars can be attached to lipids and proteinsEicosanoids & Cell Signaling:  Pain & inflammation Coagulation Vasoconstriction/dilation Aspirin Ulcers Heart attack Fatty Acid Degradation: (Beta-oxidation of fatty acids) Glucagon turns on fatty acid degradation, using stored fuels  Adipose responds by turning on triglyceride degradation  Fatty acids leave adipose, bind to albumin in the circulatory system, cells catabolize these fatty acids during the fasting state Fed = fatty acids stored as triglycerides in adipose Fasting = fatty acids released from adipose and transported in blood bound to albumin  **BRAIN AND RED BLOOD CELLS cannot access fatty acids, they cannot enter (RBC do not have mitochondria and cannot metabolize them) Lipid and Energy Metabolism: Fed = insulin = build upFasting = glucagon = break down*Fatty acids stored as triglycerides in adipose *RBC and BRAIN cannot access fatty acids o Blood brain barrier (BBB) restrict fatty acid entry in braino Red blood cells do not have mitochondria and cannot metabolize themFatty acid Catabolism:o aerobic, requires O2o Involves Beta-Oxidation to give acetyl~coA + some ATP (5)o Acetyl CoA then enters Krebs cycle to give lots of ATP (12)o This acetyl CoA also comes from glucose from glycolysis o Adipocytes (fat cells) and hepatocytes (liver cells) use extra acetyl CoA to synthesize fatty acids Remember: o Fed state: insulin is present, glucose is phosphorylated and trapped, eventually is cleaved to form pyruvate (2 3 carbon molecules, not 6)o Cori cycle: if oxygen is not present, pyruvate is converted to lactate and taken to liver where it is made into glucoseo Pyruvate can move into mitrochondria when converted to acetyl coA (Krebs Cycle)o NADH & FADH2 are produced, enter ETC where they are oxidized, oxygen is reduced to form water o ***G6P can also be stored as glycogen in the liver and skeletal muscle if not needed for ATP productiono G6P can also go down hexose monophosphate shunt for fatty acid/triglyceride synthesiso Generates NADPH needed for fatty acid synthesiso Fatty acid synthesis occurs when there is excess Acetyl CoA in the liver and adipose tissue (only stored in adipose) Oxidation of Carbon: Beta Oxidation of Fatty Acids:1. Start by removing 2 hydrogens to form CH=CH bond2. Add HOH across this CH=CH, oxidized the beta carbon 3. Remove 2 hydrogens and make C=O bond on the beta carbon4. Generate acetyl group and new fatty acid 5. These removed hydrogens are stored on FADH2 and NADH Oxidation of Fatty Acid:o


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