2 Module 22.2: Nutrient pool substrates Nutrient pool supplies molecules for catabolism, anabolism, and to fuel ATP productionATP used for metabolic makeover inside cellOrganic compounds used for 2-carbon substrate molecules for mitochondrial activities
3 The centrality of the nutrient pool to both anabolism and catabolism Structural, functional, and storage componentsTriglyceridesGlycogenProteinsOrganic compoundsthat can beabsorbed by cellsare distributed tocells throughoutthe body by thebloodstream.NutrientpoolFatty acidsGlucoseAmino acidsThree-carbon chainsTwo-carbon chainsMITOCHONDRIAATPCitricacidcycleCoenzymesElectrontransportsystemFigure Cells can break down any available substrate from the nutrient pool to obtain the energy they needO2KEY= Catabolic pathwayH2OCO2= Anabolic pathwayFigure3
4 Module 22.2: Nutrient pool substrates When nutrients absorbed from digestive tract are insufficient for cellular metabolism, energy reserves come from various cellsLiver cells store triglycerides and glycogenFatty acids and glucose can be releasedAdipocytes store triglyceridesFatty acids can be releasedSkeletal muscle cells store glycogenAmino acids can be released
5 The use of the body’s metabolic reserves to maintain normal Liver cells store triglycerides andglycogen reserves. If absorption by thedigestive tract fails to maintain normalnutrient levels, the triglycerides andglycogen are broken down and thefatty acids and glucose are released.Adipocytes convert excess fatty acids totriglycerides for storage. If absorption bythe digestive tract and reserves in theliver fail to maintain normal nurtientlevels, the triglycerides are broken downand the fatty acids released.The use of the body’s metabolicreserves to maintain normalnutrient levels in the bloodSkeletal muscles at rest metabolize fattyacids and use glucose to build glycogenreserves. Amino acids are used toincrease the number of myofibrils. If thedigestive tract, adipocytes, and liver areunable to maintain normal nutrient levels,the contractile proteins can be brokendown and amino acids released into thecirculation for use by other tissues.Nutrients obtained throughdigestion and absorptionNutrients distributedin the bloodFigure Cells can break down any available substrate from the nutrient pool to obtain the energy they needNeural tissue requires acontinuous supply ofglucose. During starvation,other tissues shift to fattyacid or amino acidcatabolism, conservingglucose for neural tissue.Cells in most tissuescontinuouslyabsorb andcatabolize glucose.Figure5
6 Module 22.2: Nutrient pool substrates Cellular catabolic and anabolic pathwaysCells must synthesize some organic moleculesInsufficient nutrients from nutrient pool and dietNutrients are often used to create 2-carbon chains for mitochondrial ATP productionOxygen required must be continuously provided by diffusion from ECFCO2 produced must diffuse out of cell to ECF
7 Module 22.2: Nutrient pool substrates Cellular nutrient dynamicsFatty acidsCan be stored as triglyceridesCan be created from acetyl-CoA and triglyceridesGlucoseCan be stored as glycogen (glycogenesis)Can be created from:Glycogen catabolism (glycogenolysis)Smaller carbon chain anabolism (gluconeogenesis)Can be used to make two 3-carbon chains for ATP production (glycolysis)
8 Module 22.2: Nutrient pool substrates Cellular nutrient dynamics (continued)Amino acidsCan be stored as proteinsCan be created from:3-carbon chainsProtein catabolism (only during starvation)
9 KEY= Catabolic pathwayA general overview of the catabolic and anabolic pathways of cells= Anabolic pathwayTriglyceridesGlycogenProteinsFatty acidscan bestored astriglycerides.Storedtriglyceridescan be brokendown intofatty acids.In glycogenesis,glycogen issynthesized fromglucose.The release ofglucose fromglycogen is calledglycogenolysis.The primary use of aminoacids is the synthesis ofproteins. Amino acids areseldom broken down if otherenergy sources are available.However, in starvation theproteins of muscle tissuesare mobilized, releasingamino acids that can becatabolized by other tissues.NutrientpoolFatty acidsGlucoseAmino acidsThe breakdownof a fatty acidreleases glyceroland acetyl-CoAsuitable for useby mitochondria.Gluconeogen-esis: glucosesynthesis fromsmaller carbonchains.Glycolysis:glucose break-down into twothree-carbonmolecules/chainsThree-carbon chainsTwo-carbon chainsFatty acid synthesisbegins with acetyl-CoA.Because this is thecommon intermediaryfor all aerobic catabolicpathways, fatty acidscan be synthesized fromexcess carbohydrates oramino acids.MITOCHONDRIAATPFigure Cells can break down any available substrate from the nutrient pool to obtain the energy they needO2 must becontinuouslyprovided bydiffusion from theECF. This requiresnormal respiratoryfunction andadequate tissueperfusion.CitricacidcycleCoenzymesElectrontransportsystemO2H2OCO2CO2 must leave the cytosol bydiffusion into the ECF, and thebloodstream must continuouslyabsorb CO2 in peripheral tissuesand eliminate it at the lungs toprevent potentially dangerouschanges in body fluid pH.Figure9
10 Module 22.2 Review a. Define nutrient pool. b. Why do cells engage in catabolism?c. Why do cells make new compounds?
11 Section 2: Digestion and Metabolism of Organic Nutrients Overview of digestive processOral cavity (mechanical processing and chemical digestion of carbohydrates and lipids)Stomach (acidic chemical digestion)Duodenum (various enzymes catalyze catabolism of all organic molecules needed by cells)Jejunum and Ileum (nutrient absorption)Nutrients stored and processed by liverLarge intestine (water reabsorbed, nutrients and vitamins produced by bacteria, feces eliminated)
12 Figure 22 Section 2 The Digestion and Metabolism of Organic Nutrients Steps in the Process of DigestionIn the oral cavity, saliva dissolves some organicnutrients, and mechanical processing withthe teeth and tongue disrupts the physicalstructure of the material and provides accessfor digestive enzymes. Those enzymes beginthe digestion of complex carbohydrates(polysaccharides) and lipids.In the stomach, the material is further brokendown physically and chemically by stomachacid and by enzymes that can operate at anextremely low pH.In the duodenum, buffers from the pancreas andliver moderate the pH of the arriving chyme, andvarious digestive enzymes are secreted by thepancreas that catalyze the catabolism ofcarbohydrates, lipids, proteins, and nucleic acids.Nutrient absorption then occurs in the smallintestine, primarily in the jejunum, and thenutrients enter the bloodstream.Indigestible materials and wastes enter the largeintestine, where water is reabsorbed and bacterialaction generates both organic nutrients andvitamins. These organic products are absorbedbefore the residue is ejected at the anus.Figure 22 Section 2 The Digestion and Metabolism of Organic NutrientsMost of the nutrients absorbed by the digestivetract end up in a tributary of the hepatic portalvein that ends at the liver. The liver absorbsnutrients as needed to maintain normal levelsin the systemic circuit.Within peripheral tissues, cells absorb thenutrients needed to maintain their nutrient pooland ongoing operations.Figure 22 Section 212
13 Module 22.3: Carbohydrates Carbohydrates are usually preferred substrates for catabolism and ATP production when restingSteps of carbohydrate digestionIn mouth, salivary amylase digests complex carbohydrates into disaccharides and trisaccharidesEnzyme active only down to pH 4.5 and denatured in stomachAt duodenum, pancreatic alpha-amylase continues carbohydrate digestion
14 Module 22.3: Carbohydrates Steps of carbohydrate digestion (continued)In jejunum, brush border enzymes finish carbohydrate digestion down to simple sugars (monosaccharides)Maltase (digests maltose: glucose + glucose)Sucrase (digests sucrose: glucose + fructose)Lactase (digests lactose: glucose + galactose)In large intestine, remaining indigestible carbohydrates (such as cellulose) are food source for colonic bacteriaProduce intestinal gas (flatus) during metabolic activities
15 Module 22.3: Carbohydrates Carbohydrate absorption and transportTransported into small intestine epithelial cellsLeave cells by facilitated diffusion through basolateral surfaceEnter cardiovascular capillaries to transport to liver in hepatic portal veinProcessed by liver to maintain glucose levels (~90 mg/dL)Released as glucose orStored as glycogen
16 Module 22.3: Carbohydrates Cellular use of digested carbohydratesGenerally preferred for catabolismProteins and lipids more important for structural components of cells and tissuesIn skeletal muscle, stored as glycogenIn most tissues, transported into cell by carrier molecule (regulated by insulin)May be converted to riboseMay be converted to 2 pyruvate molecules in glycolysisProduces 2 ATPPyruvates used by mitochondriaUses 3 O2, generates 3 CO2, 6 H2O, 34 ATP
18 The events in carbohydrate catabolism and ATP production from glucose Carbohydrates (such as glucose) are generallypreferred for catabolism because proteins andlipids are more important as structuralcomponents of cells and tissues.In most tissues, thetransport of glucose into thecell is dependent on thepresence of a carrier proteinstimulated by insulin.GLUCOSE(6-carbon)Inside the cell, the glucose may be converted toanother simple sugar, such as ribose, used tobuild glycoproteins, other structural materials,or nucleic acids. They may also be converted toglycerol for the synthesis of glycerides.InsulinOther simple sugarsATPIf needed to provide energy, the 6-carbon glucosemolecule is broken down into two 3-carbonmolecules of pyruvate. This anaerobic process,called glycolysis, yields a net gain of 2 ATP forevery glucose molecule broken down.Pyruvate(3-carbon)Pyruvate(3-carbon)Coenzyme ACO2Each pyruvate molecule can then be used bymitochondria, after conversion to acetyl-CoA.For each molecule of pyruvate processed bymitochondria, the cell gains 17 ATP, consumes3 molecules of O2, and generates 3 molecules ofCO2 and 6 molecules of water. Thus for each pairof pyruvate molecules catabolized, the cell gains34 ATP.Figure Carbohydrates are usually the preferred substrates for catabolism and ATP production under resting conditionsAcetyl-CoA(2-carbon)ATPCitricacidcycleCoenzymesElectrontransportsystemO2H2OCO2Figure 22.318
19 Module 22.3 Review a. Describe the source of intestinal gas. b. Explain the role of glycogen in cellular metabolism.c. Explain why carbohydrates are preferred over proteins and fats as an energy source.
20 Module 22.4: Catabolism of glucose GlycolysisAnaerobic process making two 3-carbon pyruvate from one 6-carbon glucoseOccurs in cytosolProduces a net gain of 2 ATPAlso produces hydrogen atoms that are transferred by NAD to mitochondria for ETS
21 Module 22.4: Catabolism of glucose Steps of glycolysisPhosphate group attached to glucose in cytosol2nd phosphate attached (cost of 2 ATP)6-carbon molecule split into two 3-carbon moleculesAnother phosphate attached to each molecule and processed further2 NADH generated2 ATP generated2 H2O releasedFurther processing creates an additional 2 ATP
22 The steps in glycolysis, the breakdown of a six-carbon glucose molecule into two three-carbon pyruvate moleculesINTERSTITIALFLUIDGlucoseATPCYTOSOLADPSteps in GlycolysisGlucose-6-phosphateAs soon as a glucose moleculeenters the cytosol, a phosphategroup is attached to the molecule.ATPADPFructose-1,6-biphosphateA second phosphate group isattached. Together, steps 1 and 2cost the cell 2 ATP.DihydroxyacetonephosphateGlyceraldehyde3-phosphateThe six-carbon chain is splitinto two three-carbon molecules,each of which then follows therest of this pathway.22NADFrom mitochondria2NAD•HTo mitochondriaAnother phosphate group isattached to each molecule, andNAD•H is generated from NAD.Energy Summary1,3-BisphosphoglycerateSteps 1 & 2:–2ATP2ADP2ATPStep 5:+2ATPFigure Glycolysis is the first step in the catabolism of the carbohydrate glucoseOne ATP molecule is formed foreach molecule processed.3-PhosphoglycerateStep 7:+2ATPThe atoms in each molecule arerearranged, releasing amolecule of water.2H2ONET GAIN:+2ATPPhosphoenolpyruvateA second ATP molecule is formedfor each molecule processed.Step 7 produces 2 ATP molecules.2ADP2ATPPyruvateTo mitochondriaFigure22
23 Module 22.4: Catabolism of glucose Summary of aerobic ATP production4 ATP from NADH produced in glycolysis24 ATP from NADH generated in citric acid cycle4 ATP from FADH2 generated in citric acid cycle2 ATP via GTP produced during enzymatic reactions34 ATP total
24 Figure 22.4.2 Glycolysis is the first step in the catabolism of the carbohydrate glucose 24
25 Module 22.4 Reviewa. List the molecular products from a glucose molecule after glycolysis.b. Identify when most of the CO2 is released during the complete catabolism of glucose.c. Explain when glycolysis may be important in cellular metabolism.
26 Module 22.5: Lipids Steps of lipid digestion In mouth, mechanical processing and chemical digestion by lingual lipaseIn stomach, lingual lipase continues to function but can only access surface of lipid drops that have formedIn duodenumBile salts break up lipid drops into smaller droplets (= emulsification)Pancreatic lipase digests triglycerides into fatty acids, monoglycerides, and glycerolForms micelles (lipid–bile salt complexes)
27 Module 22.5: Lipids Absorption and transport of digested lipids Lipids diffuse from micelle into intestinal epithelial cellIntracellular anabolic reactions synthesize new triglycerides from digested lipidsNew triglycerides packaged in chylomicrons (chylos, milky lymph, mikros, small) and released via exocytosisChylomicrons diffuse into intestinal lacteals due to their sizeTransported through lymphatic vessels (including thoracic duct) to bloodstreamEnzyme in capillaries (lipoprotein lipase) breaks down chylomicron and releases digested lipids to tissues
28 Module 22.5: Lipids Digested lipid distribution and processing Tissues that use or process digested lipidsSkeletal musclesUse fatty acids to generate ATP for contraction and to convert glucose to glycogenAdipose tissueUses fatty acids and monoglycerides to synthesize triglycerides for storageLiverAbsorbs intact chylomicrons and extracts triglycerides and cholesterol from chylomicron
29 Module 22.5: Lipids Cholesterol distribution Released from liver attached to low-density lipoproteins (LDL) for distribution to peripheral tissuesLDLs absorbed and broken down by lysosomes in cellsCholesterol extracted and usedUnused cholesterol released into bloodstreamHigh-density lipoproteins (HDL) (plasma proteins from liver) absorb peripheral cholesterol and return to liverCholesterol released again with LDLs or excreted in bileRatio of LDL/HDL and total cholesterol used diagnostically for cardiovascular problems
30 Resting skeletal muscles absorb fatty acids and break them down, using theATP provided both to power thecontractions that maintain muscletone and to convertglucose to glycogen.The chylomicronsenter the bloodstreamat the left subclavianvein, then passthrough thepulmonary circuitbefore entering thesystemic circuit.Capillary walls contain theenzyme lipoprotein lipase,which breaks down thechylomicrons and releasesfatty acids and monoglycer-ides that can diffuse into theinterstitial fluid.ThoracicductAdipocytes absorbthe monoglyceridesand fatty acids,and use them tosynthesize triglycer-ides for storage.Lipoproteins and Lipid Transport and DistributionThe liver absorbs chylomicrons, removes thetriglycerides, combines the cholesterol from thechylomicron with synthesized or recycledcholesterol, and alters the surface proteins. It thenreleases low-density lipoproteins (LDLs) intothe circulation, which deliver cholesterol toperipheral tissues. Some of the cholesterol is usedby the liver to synthesize bile salts; excesscholesterol is excreted in the bile.ChylomicronsTriglyceridesremovedThe LDLs released by theliver leave the bloodstreamthrough capillary pores orcross the endothelium byvesicular transport.CholesterolextractedLDLThe HDLs returnthe cholesterol tothe liver, where itis extracted andpackaged in newLDLs or excretedwith bile salts inbile.Once in peripheral tissues,the LDLs are absorbed.Excesscholesterol isexcreted withthe bile saltsFigure Lipids reach the bloodstream in chylomicrons; the cholesterol is then extracted and released as lipoproteinsLDLHDLHDLFrom the lacteals,the chylomicronsproceed along thelymphatic vesselsand into thethoracic duct.HighcholesterolLowcholesterolLysosomalbreakdownUsed in synthesisof membranes,hormones,other materialHDLCholesterolreleaseFigure 22.530
31 Module 22.5 Reviewa. What is the difference between a micelle and a chylomicron?b. What does the liver do with the chylomicrons it receives?c. Describe the roles of LDL and HDL.
32 Module 22.6: Lipid catabolism and synthesis Lipolysis (lipid catabolism)Triglycerides absorbed into cells through endocytosisLysosomal enzymes break down to glycerol and fatty acidsGlycerolConverted to pyruvate in glycolysis (+ 2 ATP)Fatty acidsEnzymes convert two carbons to acetyl-CoA directly (= beta-oxidation) used in mitochondriaMore efficient than glucose catabolism (6-carbon glucose = 36 ATP; 6 carbons from FAs = 51 ATP)
33 Module 22.6: Lipid catabolism and synthesis Lipid synthesis (lipogenesis)Begins with acetyl-CoAAlmost any organic substrate (lipids, amino acids, carbohydrates) can be converted to acetyl-CoAFatty acids synthesized from acetyl-CoASeries of enzymatic steps (different from beta-oxidation)Essential fatty acidsCannot be synthesized and must be obtained from dietExamples: linolenic acid (omega-3 fatty acid) and linoleic acid (omega-6 fatty acid)Structural and functional lipids created from fatty acidsFatty acids + glycerol (from glycolysis) = triglycerides
34 The major pathways for lipogenesis, the synthesis of lipids CYTOSOLThe glycerol required for triglycerideproduction is synthesized from one of theintermediate products of glycolysis.SteroidsTriglyceridesGlucoseAll of the other structural and functionallipids can be synthesized from fatty acids.GlycerolCholesterolFatty acid synthesis involves a reaction sequencequite distinct from that of beta-oxidation. As aresult, body cells cannot build every fatty acidthey can break down. For example, our cells lackthe enzymes to insert double bonds in the properlocations to synthesize two 18-carbon fatty acidssynthesized by plants: linolenic acid (anomega-3 fatty acid) or linoleic acid (anomega-6 fatty acid). However, these fatty acidsare needed to synthesize prostaglandins andsome of the phospholipids found in plasmamembranes throughout the body. They aretherefore called essential fatty acids, becausethey must be included in your diet.ProstaglandinsFatty acidsPyruvatePhospholipidsGlycolipidsCoenzyme ACO2ADPATPAcetyl-CoAFigure Fatty acids can be broken down to provide energy or converted to other lipidsCitricacidcycleStartThe synthesis of most types of lipids, includingnonessential fatty acids and steroids, beginswith acetyl-CoA. Lipogenesis can use almostany organic substrate, because lipids, aminoacids, and carbohydrates can be converted toacetyl-CoA.MITOCHONDRIAThe major pathways for lipogenesis, the synthesis of lipidsFigure34
35 Module 22.6: Lipid catabolism and synthesis Lipids as energy reservesBeta-oxidation is very efficientCan be easily stored as triglyceridesAlthough water-soluble enzymes cannot access, so not used for quick energy but for long-term storage
36 Module 22.6 Review a. Define beta-oxidation. b. What molecule plays a key reactant role in both ATP production from fatty acids and lipogenesis?c. Identify the fates of fatty acids.
37 Module 22.7: Protein digestion and amino acid metabolism Steps of protein digestionIn mouth, mechanical processing occursIn stomach:Mechanical processing due to churningStomach acid denatures protein secondary and tertiary structuresPepsin (from parietal cells) attacks certain peptide bondsDigests proteins to polypeptide and peptide chains
38 Module 22.7: Protein digestion and amino acid metabolism Steps of protein digestion (continued)In duodenum:Enteropeptidase (from duodenal epithelium) converts trypsinogen (pancreatic proenzyme) to trypsinTrypsin activates other pancreatic proenzymesChymotrypsin, carboxypeptidase, and elastaseActivated pancreatic enzymes digest specific peptide bonds producing short peptides and amino acids
39 Module 22.7: Protein digestion and amino acid metabolism Digested protein absorption and transportEpithelial brush border enzymes (peptidases) finish protein digestionAmino acids absorbed through:Facilitated diffusionCotransportReleased from epithelial cell basal surface through same cell transport mechanismsAmino acids transported to liver through intestinal capillaries to hepatic portal vein
40 Module 22.7: Protein digestion and amino acid metabolism Amino acid processing in liverControl of plasma amino acid levels is less precise than glucoseNormal range: 35–65 mg/dLCan increase after protein-rich mealLiver amino acid useSynthesize plasma proteinsCreate 3-carbon molecules for gluconeogenesis
41 Module 22.7: Protein digestion and amino acid metabolism Amino acid processing in liver (continued)Amino acid catabolismDeamination (removal of amino group)Ammonium ions released are toxicLiver enzymes convert to urea excreted into urine= Urea cycle
42 The liver does not control circulating levels of amino acids as precisely as it doesglucose concentrations. Plasma amino acidlevels normally range between 35 and 65mg/dL, but they may become elevated aftera protein-rich meal. The liver itself usesmany amino acids for synthesizing plasmaproteins, and it has all of the enzymesneeded to synthesize, convert, or catabolizeamino acids. In addition, amino acids thatcan be broken down to 3-carbon moleculescan be used for gluconeogenesis whenother sources of glucose are unavailable.Amino Acid SynthesisLiver cells and other body cells can readily synthesize the carbonframeworks of roughly half of the amino acids needed to synthesize proteins.There are 10 essential amino acids that the body either cannot synthesizeor that cannot be produced in amounts sufficient for growing children.In an aminationreaction, an ammoniumion (NH4+) is used toform an amino groupthat is attached to amolecule, yielding anamino acid.NH4+H2OH+α–KetoglutarateGlutamic acidIn a transamination, the amino group of one amino acid gets transferredto another molecule, yielding a different amino acid. The remaining carbonchain can then be broken down or used in other ways.Figure An amino acid not needed for protein synthesis may be broken down or converted to a different amino acidTransaminaseGlutamic acidOrganic acid 1Organic acid 2TyrosineFigure 22.742
43 Module 22.7 Reviewa. Name the enzyme secreted by parietal cells that is necessary for protein digestion.b. Identify the processes by which the amino group is removed.c. What happens to the ammonium ions that are removed from amino acids during deamination?
44 Module 22.8: Absorptive and postabsorptive states Period following a meal, when nutrient absorption is occurringCommonly continues for ~4 hoursInsulin is primary regulating hormone by stimulating:Glucose uptake and glycogenesisAmino acid uptake and protein synthesisOthers can be involved (GH, androgens, estrogens)Triglyceride synthesisATP can be produced from nutrient pool
45 The activities during the absorptive state following a meal KEYGlucoselevels elevated= Catabolic pathway= Anabolic pathway= StimulationInsulinLIPIDSCARBOHYDRATESPROTEINSTriglyceridesGlycogenProteinsInsulinGlucoseGlycosIInsulinInsulinAndrogensATPEstrogensGrowth hormoneLipid levelselevatedFatty acidsGlycerolAmino acidsAmino acidselevatedInsulin,Growth hormonePyruvateIn the absorptive state:CO2• Insulin stimulates(1) glucose uptakeand glycogenesis,(2) amino acid uptakeand protein synthesis,and (3) triglyceridesynthesis.InsulinFigure There are two general patterns of metabolic activity: the absorptive and postabsorptive statesAcetyl-CoAATP• Androgens, estrogens,and growth hormonealso stimulate proteinsynthesis.CitricacidcycleCoenzymesElectrontransportsystemO2O2• Glycolysis and aerobicmetabolism provide theATP needed to powercellular activities as wellas the synthesis of lipidsand proteins.MITOCHONDRIAH2OCO2Figure45
46 Module 22.8: Absorptive and postabsorptive states Period when nutrient absorption in not occurring and body relies on energy reserves (~12 hours/day)Metabolic activity focused on mobilizing energy reserves and maintaining blood glucoseLipid levels decrease = fatty acids released by adipocytesAmino acid levels decrease = amino acids released by liverGlucose levels decrease = glucose released by liverCoordinated by several hormonesGlucagon, epinephrine, glucocorticoids, growth hormone
47 Module 22.8: Absorptive and postabsorptive states Postabsorptive state (continued)Catabolism of lipids and amino acids in liver produce acetyl-CoALeads to formation of ketone bodiesDiffuse into blood and are used by other cells as energy source
48 Module 22.8: Absorptive and postabsorptive states Postabsorptive state (continued)Hormone effectsGlucocorticoidsStimulate mobilization of lipid and protein reservesEnhanced by growth hormoneGlucagonStimulates glycogenolysis and gluconeogenesisMainly in liverEpinephrineGlycogenolysis in skeletal and cardiac muscleLipolysis in adipocytes
49 Module 22.8 Reviewa. Define absorptive state and postabsorptive state.b. When and how do ketone bodies form?c. How do the absorptive and postabsorptive states maintain normal blood glucose levels?
50 Module 22.9: Vitamins Nutrition Vitamins Absorption of nutrients from foodVitaminsOrganic compounds required in very small quantities for essential metabolic activitiesTwo classesFat-soluble vitamins (A, D3, E, and K)Water-soluble vitamins (B vitamins and C)
51 Module 22.9: Vitamins Fat-soluble vitamins Absorbed primarily from digestive tract with micellesVegetables are potential sourcesVitamin D3 produced in skinVitamin K produced by intestinal bacteriaStored in lipid depositsGives large bodily reservesAvitaminosis (vitamin deficiency) rarely occurs with fat-soluble vitaminsHypervitaminosis can occur as metabolism from lipid reserves takes time
52 Figure 22.9.2 Vitamins are essential to the function of many metabolic pathways 52
53 Figure 22.9.2 Vitamins are essential to the function of many metabolic pathways 53
54 Module 22.9: Vitamins Water-soluble vitamins Most are components of coenzymesNutritional sourcesB vitamins are found in meat, eggs, and dairy productsVitamin C is found in citrus fruitsSignificant stores of only vitamins B12 and CIntestinal bacteria produce four of nine B vitamins
55 Module 22.9: Vitamins Water-soluble vitamins (continued) Readily exchanged between body fluid compartmentsMost easily absorbed across intestinal wallB12 requires transport with intrinsic factorExcess amounts excreted in urineHypervitaminosis rarely occurs with water-soluble vitamins
56 Figure 22.9.4 Vitamins are essential to the function of many metabolic pathways 56
57 Figure 22.9.4 Vitamins are essential to the function of many metabolic pathways 57
58 Figure 22.9.4 Vitamins are essential to the function of many metabolic pathways 58
59 Module 22.9 Review a. Define nutrition. b. Identify the two classes of vitamins.c. If vitamins do not provide a source of energy, what is their role in nutrition?
61 Module 22.10: Nutrition and diet Balanced dietContains all ingredients required for homeostasisSubstrates for ATP productionEssential amino acidsFatty acidsVitaminsElectrolytesWaterMalnutritionUnhealthy state from inadequate or excessive nutrient absorption
62 Module 22.10: Nutrition and diet MyPyramid.gov Steps to a Healthier YouU.S. Dept. of Agriculture personalized eating plans based on current Dietary Guidelines for AmericansColor-coded vertical food groups indicate recommended proportionsGrains (orange)Vegetables (green)Fruits (red)Milk products (blue)Meat and beans (purple)Oils (yellow)
63 GRAINS VEGETABLES FRUITS MILK MEAT & BEANS The MyPyramid.gov Steps to a Healthier YouActivityFigure Proper nutrition depends on eating a balanced dietGRAINSOILSVEGETABLESFRUITSMILKMEAT & BEANSMake half your grains wholeVary your veggiesFocus on fruitsGet your calcium-rich foodsGo lean with proteinsFigure63
65 Figure 22.10.1 Proper nutrition depends on eating a balanced diet 65
66 Figure 22.10.1 Proper nutrition depends on eating a balanced diet 66
67 Module 22.10: Nutrition and diet Food energy contentCommon units are calories or joules (0.239 calories)1 calorie = energy to raise temperature of 1 g of water by 1°CKilocalories (kcal or Calorie) or kilojoule (kJ) are used for whole-body metabolism1 kCal = energy to raise temperature of 1 kg of water by 1°CEnergy yield of different nutrients variesCarbohydrates: 4.18 Cal/gProteins: 4.32 Cal/gLipids: 9.46 Cal/gAverage adult needs 2000–3000 Cal daily
68 Figure 22.10.2 Proper nutrition depends on eating a balanced diet 68
69 Figure 22.10.3 Proper nutrition depends on eating a balanced diet 69
70 Module 22.10: Nutrition and diet Different nutritional proteinsComplete proteinsProvide all essential amino acidsFrom beef, fish, poultry, eggs, and milkIncomplete proteinsDeficient in one or more essential amino acidsMostly from plant sourcesVegetarians and vegans must closely monitor sufficient combination of plant protein sources
71 Module 22.10 Review a. Define balanced diet. b. Distinguish between a complete protein and an incomplete protein.c. Of these three—carbohydrates, lipids, or proteins—which one releases the greatest number of Calories per gram during catabolism?
72 CLINICAL MODULE 22.11: Metabolic disorders Disorders related to diet and digestionEating disorders (psychological problems resulting in abnormal eating habits)Anorexia nervosaSelf-induced starvation or lack/loss of appetiteWeights commonly 30% below normalMost common in adolescent Caucasian femalesPatients convinced they are too fatBulimiaBinge eating followed by vomiting, or use of laxatives or diureticsMore common than anorexia
73 CLINICAL MODULE 22.11: Metabolic disorders Disorders related to diet and digestion (continued)ObesityCondition of being >20% over ideal weightDue to energy input > energy outputU.S. Centers for Disease Control (CDC) estimate:32% of men and 35% of women are obeseTwo major categoriesRegulatory obesity (failure to regulate food input)Most common formMetabolic obesity (secondary to underlying malfunction in cell/tissue metabolism)
74 CLINICAL MODULE 22.11: Metabolic disorders Disorders related to diet and digestion (continued)Elevated cholesterol levelsMay cause development of atherosclerosis and coronary artery diseaseRecommended <300 mg/dayHigh LDL levels can lead to deposits in peripheral tissues such as blood vessels
75 CLINICAL MODULE 22.11: Metabolic disorders Nutritional/metabolic disordersPhenylketonuria (PKU)Inability to convert phenylalanine to tyrosineEssential to synthesis of:NorepinephrineEpinephrineDopamineMelaninProtein deficiency diseaseLiver unable to produce plasma proteins leading to edemaExample: kwashiorkor
76 CLINICAL MODULE 22.11: Metabolic disorders Nutritional/metabolic disorders (continued)KetoacidosisAcidification of blood due to ketone body productionLeads to ketosisOccurs when glucose supplies are limitedFatty acid and amino acid catabolism in liver leads to acetyl-CoA production and generation of ketonesIn extreme cases, may cause coma, cardiac arrhythmias, and deathGout (insoluble urea crystal formation)Commonly in joints (gouty arthritis)
77 CLINICAL MODULE 22.11 Review a. Identify and briefly define two eating disorders.b. Define protein deficiency disease and cite an example.c. Briefly describe phenylketonuria (PKU).
78 Section 3: Energetics and Thermoregulation Study of energy flow and energy conversionBasal metabolic rate (BMR)Minimum resting energy expenditure of awake, alert personVarious factors can affect BMRPerson’s size or weightLevel of physical activityCommon benchmark for energetics studiesDirect measurement methodMeasuring respiratory activity and assuming Cal/L oxygen consumedAverage is 70 Cal/hr
79 Estimated Calories expended The approximate number ofCalories expended per hourat various levels of physicalexertion1000Estimated Calories expendedby a 70-kg individual800600Calories per hour400200Figure 22 Section 3 Energetics and ThermoregulationRestingSlowwalkingSpeedwalkingClimbingstairsJoggingCompetitiveswimmingFigure 22 Section79
80 Section 3: Energetics and Thermoregulation Homeostatic control of body temperatureMaintaining food intake adequate to support body activitiesCatabolic reactions generating ATP40% of energy used to form ATP60% released as heatMany enzymes and metabolic activities require a specific temperature range
81 Module 22.12: Appetite regulation Appetite is controlled by two areas of hypothalamusFeeding centerSatiety centerCauses inhibition of feeding centerRegulation of appetite can occur on two levelsShort-term regulationLong-term regulation
82 Module 22.12: Appetite regulation Short-term regulation of appetiteStimulation of satiety centerElevation of blood glucose levelsHormones of digestive tract (like CCK)Digestive tract wall stretchingStimulation of feeding centerNeurotransmittersExample: neuropeptide Y or NPY from hypothalamusGhrelinHormone secreted by gastric mucosa when stomach is empty
83 Module 22.12: Appetite regulation Long-term regulation of appetiteLeptinPeptide hormone secreted by adipocytesStimulates satiety center and suppresses appetiteEffects are gradual
84 Mechanisms in the control of appetite Short-Term Regulation of AppetiteStimulation of Satiety CenterHypothalamusSatiety centerElevated bood glucose levels depressappetite, and low blood glucosestimulates appetite. The likelymechanism is glucose entry stimulatingthe neurons of the satiety center.Several hormones of the digestive tract,including CCK, suppress appetiteduring the absorptive state.Feeding centerStimulation of stretch receptors alongthe digestive tract, especially in thestomach, causes a sense of satiationand suppresses appetite.Long-Term Regulation of AppetiteStimulation of Feeding CenterSeveral neurotransmitters havebeen linked to appetite regulation.Neuropeptide Y (NPY), for example,is a hypothalamic neurotransmitter that(among other effects) stimulates thefeeding center and increases appetite.Figure The control of appetite is complex and involves both short-term and long-term mechanismsWhen appetite outpaces energy usage,excess calories are stored as fat inadipose tissue. Leptin is a peptidehormone released by adipose tissuesas they synthesize triglycerides. In theCNS it stimulates the satiety centerand suppresses appetite. The effectsare gradual, and it is probably involvedin long-term regulation of food intake.The hormone ghrelin (GREL-in),secreted by the gastric mucosa,stimulates appetite. Ghrelin levels arehigh when the stomach is empty, anddecline as the stomach fills.Mechanisms in the controlof appetiteFigure 22.1284
85 Module Reviewa. What hormone inhibits the satiety center and stimulates appetite in the short-term?b. Describe leptin and its effect on appetite.c. How might a lack of Neuropeptide Y in the hypothalamus affect the control of appetite?
86 Module 22.13: Thermodynamics About 40% of energy from catabolism is captured as ATPRest is heat that warms surrounding tissuesTo maintain body temperature, heat loss and heat production must be in balanceVarying activities and environmental conditions affect heat balance
87 Module 22.13: Thermodynamics Primary heat transfer mechanismsRadiation (infrared radiation from warm objects)~50% of body heat lost by radiationConvection (conductive heat loss due to air movement)Evaporation (water loss from moist areas)Insensible perspiration (from alveoli and skin)Sensible perspiration (from sweat glands)Conduction (direct transfer through physical contact)
88 Primary Mechanisms of Heat Transfer Radiation: Warm objects lose heat energy as infraredradiation. More than 50 percent of the heat you loseindoors is attributable to radiation.The primarymechanisms ofheat transferbetween the bodyand the surroundingenvironmentConvection: This process results from conductive heatloss to the air that overlies the surface of the body.Convection accounts for roughly 15 percent of thebody’s heat loss indoorsEvaporation: When water changes from a liquid to avapor, evaporation absorbs energy and cools thesurface where it occurs. Insensible perspiration—theevaporation of water across epithelia, from alveolarsurfaces, and from the skin—accounts for roughly 20percent of heat loss indoors. The water in sweat istermed sensible perspiration.Figure To maintain a constant body temperature, heat gain and heat loss must be in balanceConduction: This process, which is the direct transferof energy through physical contact, is generally not aneffective mechanism for gaining or losing heat. Whenyou are standing, conductive losses are negligible.Figure88
89 Underlying physical or environmental condition Thermoregulatory The effects of afailure to controlbody temperatureUnderlying physical orenvironmental condition°F°CThermoregulatorycapabilitiesMajorphysiological effectsDeath114Severely impairedProteins denature44CNS damage110ConvulsionsHeat stroke42ImpairedCell damage106Disease-related fevers40DisorientationSevere exercise102Active childrenEffective38Normal range (oral)98Systems normal36Early mornings incold weather9434DisorientationImpairedLoss ofmuscle control9032Figure To maintain a constant body temperature, heat gain and heat loss must be in balanceSevere exposureSeverely impaired8630Loss ofconsciousnessHypothermiafor open heartsurgery8228Cardiac arrest2678LostDeath2474Figure89
90 Module 22.13 Review a. Define insensible perspiration. b. What heat transfer process accounts for about one-half of an individual’s heat loss when indoors?c. How is heat loss different between conduction and convection?
91 Module 22.14: Thermoregulation Heat loss and heat gain involve many systemsCoordinated by two centers in hypothalamus preoptic areaHeat-loss centerHeat-gain center
92 Module 22.14: Thermoregulation Responses to high body temperatureBehavioral changes (moving to shade, pool, etc.)Vasodilation and shunting of blood to skin surfaceRadiational and convective heat loss increasesSweat productionIncreases evaporative heat lossRespiratory heat lossDepth of respiration increases to increase evaporative heat loss from lungs
93 Preoptic areaHeat-loss centerHeat-gain centerResponses Coordinated by the Heat-LossCenter When Body Temperature RisesBehavioral Changes: A senseof discomfort leads to behavioralresponses—getting into the shade, goinginto the water, or taking other steps thatreduce body temperature.Vasodilation and Shunting of Blood toSkin Surface: The inhibition of thevasomotor center causes peripheralvasodilation, and warm blood flows to thesurface of the body. The skin takes on areddish color, skin temperatures rise, andradiational and convective losses increase.RadiationConvectionSweat Production: As blood flow to theskin increases, sweat glands are stimulatedto increase their secretory output. Theperspiration flows across the body surface,and evaporative heat losses accelerate.Maximal secretion, if completely evaporated,would remove 2320 Cal per hour.Figure Hypothalamic thermoregulatory centers adjust rates of heat gain and heat lossRespiratory Heat Loss: The respiratorycenters are stimulated, and the depth ofrespiration increases. Often, the individualbegins respiring through an open mouthrather than through the nasal passageways,increasing evaporative heat losses throughthe lungs.Figure 22.1493
94 Module 22.14: Thermoregulation Responses to low body temperatureIncreased generation of body heatNonshivering thermogenesisRelease of hormones that increase metabolic rateShivering thermogenesisIncreased muscle tone leading to brief contractionsConservation of body heatVasoconstriction of vessels near body surfaceCountercurrent exchange of heatTransfer of heat from deep arteries to deep veins
95 Responses Coordinated by the Heat-Gain Center When Body Temperature FallsThe heat-gain center responds to low bodytemperature in two ways:Increased Generation of Body HeatNonshivering thermogenesis (ther-mō-JEN-e-sis)involves the release of hormones that increase themetabolic activity of all tissues. Sympathetic stimulationof the adrenal medullae releases epinephrine, whichquickly increases the rates of glycogenolysis in liver andskeletal muscle and the metabolic rate of most tissues.In shivering thermogenesis, a gradual increase inmuscle tone increases the energy consumption ofskeletal muscle tissue throughout your body. Bothagonists and antagonists are involved, and muscle tonegradually increases to the point at which stretch receptorstimulation will produce brief, oscillatory contractionsof antagonistic muscles. In other words, you begin toshiver. Shivering can elevate body temperature quiteeffectively, increasing the rate of heat generation by asmuch as 400 percent.RadiationConvectionConservation of Body HeatThe vasomotor center decreases blood flow to the dermis,thereby reducing losses by radiation and convection. Theskin cools, and with blood flow restricted, it may take on abluish or pale color. The epithelial cells are not damaged,because they can tolerate extended periods at temperaturesas low as 25°C (77°F) or as high as 49°C (120°F).Warmblood fromtrunkWarm bloodreturnsto trunkFigure Hypothalamic thermoregulatory centers adjust rates of heat gain and heat loss37°C36.5°–37°CThe deep veins lie alongside the deep arteries, and heatis conducted from the warm blood flowing outward to thelimbs to the cooler blood returning from the periphery.This arrangement traps the heat close to the body coreand dramatically reduces heat loss. The transfer of heat,water, or solutes between fluids moving in oppositedirections is called countercurrent exchange.H e a t t r a n s f e r24°C23°CCool bloodreturnsto trunkCooled bloodto distalcapillariesFigure 22.1495
96 Module Reviewa. Name the heat conservation mechanism that results in the conduction of heat from deep arteries to adjacent deep veins in the limbs.b. Describe the role of nonshivering thermogenesis in regulating body temperature.c. Predict the effect of peripheral vasodilation on an individual’s body temperature.