Chapter 27: Metabolism and Nutrition

Transcription

1 Chapter 27: Metabolism ad Nutritio

2 Metabolism Metabolism refers to all chemical reactio occurrig i body Catabolism break dow complex molecules Exergoic produce more eergy tha they cosume Aabolism combie simple molecules ito complex oes Edergoic cosume more eergy tha they produce Adeosie triphosphate (ATP) eergy currecy ADP + P + eergy ATP Copyright 2009, Joh Wiley & Sos, Ic.

3 Role of ATP i likig aabolic ad catabolic reactios

4 Eergy trasfer Oxidatio-reductio or redox reactios Oxidatio removal of electros Decrease i potetial eergy Dehydrogeatio removal of hydroges Liberated hydroge trasferred by coezymes Nicotiamide adeie diucleotide (NAD) Flavi adeie diucleotide (FAD) Glucose is oxidized Reductio additio of electros Icrease i potetial eergy

5 3 Mechaisms of ATP geeratio 1. Substrate-level phosphorylatio Trasferrig high-eergy phosphate group from a itermediate directly to ADP 2. Oxidative phosphorylatio Remove electros ad pass them through electro trasport chai to oxyge 3. Photophosphorylatio Oly i chlorophyll-cotaiig plat cells Copyright 2009, Joh Wiley & Sos, Ic.

6 Carbohydrate metabolism Fate of glucose depeds o eeds of body cells ATP productio or sythesis of amio acids, glycoge, or triglycerides GluT trasporters brig glucose ito the cell via facilitate diffusio Isuli causes isertio of more of these trasporters, icreasig rate of etry ito cells Glucose trapped i cells after beig phosphorylated Copyright 2009, Joh Wiley & Sos, Ic.

7 Glucose catabolism / cellular respiratio 1. Glycolysis Aaerobic respiratio does ot reuire oxyge 2. Formatio of acetyl coezyme A 3. Krebs cycle reactios 4. Electro trasport chai reactios Aerobic respiratio reuires oxyge Copyright 2009, Joh Wiley & Sos, Ic.

8 Overview of cellular respiratio Copyright 2009, Joh Wiley & Sos, Ic.

9 1 Glucose 1 GLYCOLYSIS 2 2 ATP NADH + 2 H + 2 Pyruvic acid 2 FORMATION OF ACETYL COENZYME A 2 Acetyl coezyme A 3 KREBS CYCLE 2 2 CO 2 NADH + 2 H + 2 ATP 4 CO 2 6 NADH 2 FADH H + Electros 4 ELECTRON TRANSPORT CHAIN e e e 6 O 2 32 or 34 ATP 6 H 2 O

10 Glycolysis 1. Glycolysis Splits 6-carbo glucose ito 2 3-carbo molecules of pyruvic acid Cosumes 2 ATP but geerates 4 10 reactios Fate of pyruvic acid depeds o oxyge availability If oxyge is scarce (aaerobic), reduced to lactic acid Hepatocytes ca covert it back to pyruvic acid If oxyge is pletiful (aerobic), coverted to acetyl coezyme A Copyright 2009, Joh Wiley & Sos, Ic.

11 Cellular respiratio begis with glycolysis

12 The 10 reactios of glycolysis Copyright 2009, Joh Wiley & Sos, Ic.

13 6 CH 2 OH H 5 O H H 4 1 HO OH H OH 3 2 H OH Glucose (1 molecule) CH 2 O P C O CH 2 OH Dihydroxyacetoe phosphate 5 6 H C O HCOH CH 2 O P Glyceraldehyde 3-phosphate 2 NAD P 2 NADH + 2H + ATP 1 ADP P OH 2 C O H H HO OH H H OH H OH Glucose 6-phosphate 2 P OH 2 C 6 O 1 CH 2 OH 5 2 H H HO OH 4 3 OH H Fructose 6-phosphate Phosphofructokiase 3 ATP ADP P OH 2 C O CH 2 O P CH 2 O P HCOH C O O P 1, 3-Bisphosphoglyceric acid (2 molecules) 7 2 ADP 2 ATP CH 2 O P HCOH 3-Phosphoglyceric acid COOH (2 molecules) 8 CH 2 OH HCO P 2-Phosphoglyceric acid COOH (2 molecules) 9 CH 2 C O P Phosphoeolpyruvic acid COOH (2 molecules) 2 ADP 10 2 ATP H H OH 4 HO H OH Fructose 1, 6-bisphosphate CH 3 C O COOH Pyruvic acid (2 molecules)

14 Formatio of Acetyl coezyme A 2. Formatio of Acetyl coezyme A Each pyruvic acid coverted to 2-carbo acetyl group Remove oe molecule of CO 2 as a waste product Each pyruvic acid also loses 2 hydroge atoms NAD + reduced to NADH + H + Acetyl group attached to coezyme A to form acetyl coezyme A (acetyl CoA) Copyright 2009, Joh Wiley & Sos, Ic.

15 Fate of pyruvic acid

16 The Krebs cycle 3. The Krebs cycle Also kow as citric acid cycle Occurs i matrix of mitochodria Series of redox reactios 2 decarboxylatio reactios release CO 2 Reduced coezymes (NADH ad FADH 2 ) are the most importat outcome Oe molecule of ATP geerated by substratelevel phosphorylatio Copyright 2009, Joh Wiley & Sos, Ic.

17 The Krebs Cycle Copyright 2009, Joh Wiley & Sos, Ic.

18 The Eight reactios of the Krebs cycle Copyright 2009, Joh Wiley & Sos, Ic.

19 CH 3 C O COOH Pyruvic acid NAD + NADH + H + To electro trasport chai CO 2 CoA C O CH 3 Acetyl coezyme A Oxaloacetic acid COOH NADH + H + C O CH 2 NAD + COOH H 2 O COOH HCOH 8 1 CoA H 2 C COOH HOC COOH H 2 C COOH Citric acid To electro trasport chai CH 2 Malic acid COOH H 2 O 7 COOH CH Fumaric acid HC COOH KREBS CYCLE 2 H 2 C COOH HC COOH HOC COOH H Isocitric acid 3 FADH 2 6 FAD H 2 C COOH H 2 C COOH Succiic acid ADP CoA 5 GTP CO 2 H 2 C COOH GDP CH 2 O C S CoA ATP Succiyl CoA 4 NAD + NADH + H + CO 2 H 2 C COOH HCH O C COOH Alpha-ketoglutaric acid NAD + NADH + H + To electro trasport chai

20 Electro trasport chai 4. Electro trasport chai Series of electro carriers i ier mitochodrial membrae reduced ad oxidized As electros pass through chai, exergoic reactios release eergy used to form ATP Chemiosmosis Fial electro acceptor is oxyge to form water Copyright 2009, Joh Wiley & Sos, Ic.

21 Chemiosmosis Carriers act as proto pumps to expel H + from mitochodrial matrix Creates H + electrochemical gradiet cocetratio gradiet ad electrical gradiet Gradiet has potetial eergy proto motive force As H + flows back ito matrix through membrae, geerates ATP usig ATP sythase Copyright 2009, Joh Wiley & Sos, Ic.

22 Outer membrae Ier membrae Matrix High H + cocetratio betwee ier ad outer mitochodrial membraes 2 H + H + H + chael Ier mitochodrial membrae Electro trasport chai (icludes proto pumps) 1 Eergy from NADH + H + 3 ADP + P Low H + cocetratio i matrix of mitochodrio ATP sythase ATP

23 The actios of the three proto pumps ad ATP sythase i the ier membrae of mitochodria Ier mito- chodrial membrae Space betwee outer ad ier mitochodrial membraes Mitochodrial matrix e NAD H + chael + H + H H Q NADH + H + e H + e Cyt c 1 1/2 O 2 3 H 2 O ATP sythase NADH dehydrogease Cytochrome b-c 1 Cytochrome oxidase complex: FMN ad complex: cyt b, cyt c 1, complex: cyt a, five Fe-S ceters ad a Fe-S ceter cyt a 3,ad two Cu e e 3 ADP + P ATP Copyright 2009, Joh Wiley & Sos, Ic.

24 Summary of cellular respiratio

25 Glucose aabolism Glucose storage: glycogeesis Polysaccharide that is the oly stored carbohydrate i humas Isuli stimulates hepatocytes ad skeletal muscle cells to sythesize glycoge Glucose release: glycogeolysis Glycoge stored i hepatocytes broke dow ito glucose ad release ito blood Copyright 2009, Joh Wiley & Sos, Ic.

26 Glycogeesis ad glycogeolysis

27 Formatio of glucose from proteis ad fats: glucoeogeesis Glycerol part of triglycerides, lactic acid, ad certai amio acids ca be coverted by the liver ito glucose Glucose formed from ocarbohydrate sources Stimulated by cortisol ad glucago

28 Lipid metabolism Trasport by lipoproteis Most lipids opolar ad hydrophobic Made more water-soluble by combiig them with proteis to form lipoproteis Proteis i outer shell called apoproteis (apo) Each has specific fuctios All essetially are trasport vehicles

29 Apoproteis Apoproteis categorized ad amed accordig to desity (ratio of lipids to proteis) Chylomicros Form i small itestie mucosal epithelial cells Trasport dietary lipids to adipose tissue Very low-desity lipoproteis (VLDLs) Form i hepatocytes Trasport edogeous lipids to adipocytes Low-desity lipoproteis (LDLs) bad cholesterol Carry 75% of total cholesterol i blood Deliver to body cells for repair ad sythesis Ca deposit cholesterol i fatty plaues High-desity lipoproteis (HDLs) good cholesterol Remove excess cholesterol from body cells ad blood Deliver to liver for elimiatio Copyright 2009, Joh Wiley & Sos, Ic.

30 Lipid Metabolism 2 sources of cholesterol i the body Preset i foods Sythesized by hepatocytes As total blood cholesterol icreases, risk of coroary artery disease begis to rise Treated with exercise, diet, ad drugs Lipids ca be oxidized to provide ATP Stored i adipose tissue if ot eeded for ATP Major fuctio of adipose tissue to remove triglycerides from chylomicros ad VLDLs ad store it util eeded 98% of all body eergy reserves Copyright 2009, Joh Wiley & Sos, Ic.

31 Lipid Metabolism Lipid catabolism: lipolysis Triglycerides split ito glycerol ad fatty acids Must be doe for muscle, liver, ad adipose tissue to oxidize fatty acids Ehaced by epiephrie ad orepiephrie Lipid aabolism: lipogeesis Liver cells ad adipose cells sythesize lipids from glucose or amio acids Occurs whe more calories are cosumed tha eeded for ATP productio Copyright 2009, Joh Wiley & Sos, Ic.

32 Pathways of lipid metabolism

33 Protei metabolism Amio acids are either oxidized to produce ATP or used to sythesize ew proteis Excess dietary amio acids are ot excreted but coverted ito glucose (glucoeogeesis) or triglycerides (lipogeesis) Protei catabolism Proteis from wor out cells broke dow ito amio acids Before eterig Krebs cycle amio group must be removed deamiatio Produces ammoia, liver cells covert to urea, excreted i urie Copyright 2009, Joh Wiley & Sos, Ic.

34 Various poits at which amio acids eter the Krebs cycle for oxidatio

35 Protei aabolism Carried out i ribosomes of almost every cell i the body 10 essetial amio acids i the huma Must be preset i the diet because they caot be sythesized Complete protei cotais sufficiet amouts of all essetial amio acids beef, fish, poultry, eggs Icomplete protei does ot leafy gree vegetables, legumes, grais 10 other oessetial amio acids ca be sythesized by body cells usig trasamiatio Copyright 2009, Joh Wiley & Sos, Ic.

36 Key molecules at metabolic crossroads 3 molecules play pivotal roles i metabolism Stad at metabolic crossroads reactios that occur or ot deped o utritioal or activity status of idividual 1. Glucose 6-phosphate Made shortly after glucose eters body cell 4 fates sythesis of glycoge, release of glucose ito blood stream, sythesis of ucleic acids, glycolysis Copyright 2009, Joh Wiley & Sos, Ic.

37 Key molecules at metabolic crossroads 2. Pyruvic acid If there is eough oxyge, aerobic cellular respiratio occurs If there is ot eough oxyge, aaerobic reactios ca produce lactic acid, produce alaie or glucoeogeesis 3. Acetyl Coezyme A Whe ATP is low ad oxyge pletiful, most pyruvic acid goes to ATP productio via Acetyl CoA Acetyl CoA os the etry ito the Krebs cycle Ca also be used for sythesis of certai lipids Copyright 2009, Joh Wiley & Sos, Ic.

38 Metabolic adaptatios Durig the absorptive state igested utriets are eterig the blood stream Glucose readily available for ATP productio Durig postabsorptive state absorptio of utriets from GI tract complete Eergy eeds must be met by fuels i the body Nervous system ad red blood cells deped o glucose so maitaiig steady blood glucose critical Effects of isuli domiate Copyright 2009, Joh Wiley & Sos, Ic.

39 Metabolism durig absorptive state Soo after a meal utriets eter blood Glucose, amio acids, ad triglycerides i chylomicros 2 metabolic hallmarks Oxidatio of glucose for ATP productio i all body cells Storage of excess fuel molecules i hepatocytes, adipocytes, ad skeletal muscle cells Pacreatic beta cells release isuli Promotes etry of glucose ad amio acids ito cells Copyright 2009, Joh Wiley & Sos, Ic.

40 Pricipal metabolic pathways durig the absorptive state Copyright 2009, Joh Wiley & Sos, Ic.

41 MOST TISSUES Blood SKELETAL MUSCLE GLUCOSE Storage Oxidatio GLUCOSE 1 4 CO2 + H2O + Glycoge Proteis GASTROINTESTINAL TRACT 8 AMINO ACIDS GLUCOSE TRIGLYCERIDES (i chylomicros) HEPATOCYTES IN LIVER 6 7 Glucose Keto acids Proteis 2 Fatty acids CO2 + H2O + ATP Glyceraldehyde Glycoge 3-phosphate Triglycerides 3 VLDLs 4 5 Glucose Triglycerides Triglycerides Fatty acids ADIPOSE TISSUE Glyceraldehyde 3-phosphate Triglycerides ATP

42 Metabolism durig postabsorptive state About 4 hours after the last meal absorptio i small itestie early complete Blood glucose levels start to fall Mai metabolic challege to maitai ormal blood glucose levels Glucose productio Breakdow of liver glycoge, lipolysis, glucoeogeesis usig lactic acid ad/or amio acids Glucose coservatio Oxidatio of fatty acids, lactic acid, amio acids, ketoe bodies ad breakdow of muscle glycoge Copyright 2009, Joh Wiley & Sos, Ic.

43 Pricipal metabolic pathways durig the postabsorptive state Copyright 2009, Joh Wiley & Sos, Ic.

44 ADIPOSE TISSUE SKELETAL MUSCLE TISSUE Triglycerides HEART 2 Fatty acids Glycerol Blood Muscle proteis Fastig or starvatio 4 LIVER 7 Amio acids 5 Fatty acids ATP 9 Fatty acids Lactic acid 8 Keto acids 1 Ketoe bodies ATP ATP 8 Ketoe bodies OTHER TISSUES 4 Amio acids Fatty acids O2 (aaerobic) Lactic acid ATP Glucose Pyruvic acid (aerobic) 6 3 ATP + O2 ATP ATP Liver glycoge Lactic acid Glucose 6-phosphate Glycerol ATP Amio acids 4 Muscle glycoge 5 Fatty acids 5 Ketoe bodies NERVOUS TISSUE Glucose Ketoe bodies 8 ATP Starvatio ATP Proteis ATP 8 ATP

45 Hormoes ad autoomic ervous system regulate metabolism durig postabsorptive state As blood glucose declie, isuli secretio falls Glucago icreases release of glucose ito blood via glucoeogeesis ad glycogeolysis Sympathetic erve edigs of ANS release orepiephrie ad adreal medulla releases epiephrie ad orepiephrie Stimulate lipolysis, glycoge breakdow Copyright 2009, Joh Wiley & Sos, Ic.

46 Heat ad eergy balace Heat form of eergy that ca be measured as temperature ad ca be expressed i calories calorie (cal) amout of heat reuired to raise 1 gram of water 1 C Kilocalorie (kcal) or Calorie (Cal) is 1000 calories Metabolic rate overall rate at which metabolic reactios use eergy Some eergy used to make ATP, some lost as heat Basal metabolic rate (BMR) measuremet with body i uiet, restig, fastig coditio Copyright 2009, Joh Wiley & Sos, Ic.

47 Body temperature homeostasis Despite wide fluctuatios i evirometal temperatures, homeostatic mechaisms maitai ormal rage for iteral body temperature Core temperature (37 C or 98.6 F) versus shell temperature (1-6 C lower) Heat produced by exercise, some hormoes, sympathetic ervous system, fever, igestio of food, youger age, etc. Copyright 2009, Joh Wiley & Sos, Ic.

48 Heat ad egery balace Heat ca be lost through Coductio to solid materials i cotact with body Covectio trasfer of heat by movemet of a gas or liuid Radiatio trasfer of heat i form of ifrared rays Evaporatio exhaled air ad ski surface (isesible water loss) Hypothalamic thermostat i preoptic area Heat-losig ceter ad heat-promotig ceter Copyright 2009, Joh Wiley & Sos, Ic.

49 Thermoregulatio If core temperature declies Ski blood vessels costrict Release of thyroid hormoes, epiephrie ad orepiephrie icreases cellular metabolism Shiverig If core body temperature too high Dilatio of ski blood vessels Decrease metabolic rate Stimulate sweat glads Copyright 2009, Joh Wiley & Sos, Ic.

50 Negative feedback mechaisms that coserve heat ad icrease icrease productio

51 Nutritio Nutriets are chemical substaces i food that body cells use for growth, maiteace, ad repair 6 mai types 1. Water eeded i largest amout 2. Carbohydrates 3. Lipids 4. Proteis 5. Mierals 6. Vitamis Essetial utriets must be obtaied from the diet Copyright 2009, Joh Wiley & Sos, Ic.

52 Guidelies for healthy eatig We do ot kow with certaity what levels ad types of carbohydrates, fat ad protei are optimal Differet populatios aroud the world eat radically differet diets adapted to their particular lifestyle Basic guidelies Eat a variety of foods Maitai a healthy weight Choose foods low i fat, saturated fat ad cholesterol Eat plety of vegetables, fruits ad grai products Use sugars i moderatio oly Copyright 2009, Joh Wiley & Sos, Ic.

53 My Pyramid Copyright 2009, Joh Wiley & Sos, Ic.

54 Mierals Iorgaic elemets that occur aturally i Earth s crust Eat foods that cotai eough calcium, phosphorus, iro ad iodie Excess amouts of most mierals are excreted i urie ad feces Major role of mierals to help regulate ezymatic reactios

55 Vitamis Orgaic utriets reuired i small amouts to maitai growth ad ormal metabolism Do ot provide eergy or serve as body s buildig materials Most are coezymes Most caot be sythesized by the body Vitami K produced by bacteria i GI tract Some ca be assembled from provitamis No sigle food cotais all the reuired vitamis 2 groups Fat-soluble A, D, E, K Water-soluble several B vitamis ad vitami C