1. http://www.teachersdomain.org/resource/nv sn6.sci.bio.fuel/ Chapter 25: Metabolism and Nutrition

2. Copyright 2009, John Wiley & Sons, Inc. Metabolism Metabolism – refers to all chemical reaction occurring in body  Catabolism – break down complex molecules Exergonic – produce more energy than they consume  Anabolism – combine simple molecules into complex ones Endergonic – consume more energy than they produce Adenosine triphosphate (ATP)  “energy currency”  ADP + P + energy ↔ ATP

3. Copyright 2009, John Wiley & Sons, Inc. Role of ATP in linking anabolic and catabolic reactions Each cell has about 1 billion ATP molecules that last for less than one minute

4. Copyright 2009, John Wiley & Sons, Inc. Energy transfer Oxidation-reduction or redox reactions  Oxidation – removal of electrons Decrease in potential energy Dehydrogenation – removal of hydrogens Liberated hydrogen transferred by coenzymes  Nicotinamide adenine dinucleotide (NAD)  Flavin adenine dinucleotide (FAD) Glucose is oxidized  Reduction – addition of electrons Increase in potential energy

5. Copyright 2009, John Wiley & Sons, Inc. 3 Mechanisms of ATP generation 1. Substrate-level phosphorylation Transferring high-energy phosphate group from an intermediate directly to ADP 2. Oxidative phosphorylation Remove electrons and pass them through electron transport chain to oxygen 3. Photophosphorylation Only in chlorophyll-containing plant cells

6. Copyright 2009, John Wiley & Sons, Inc. Carbohydrate metabolism Fate of glucose depends on needs of body cells  ATP production or synthesis of amino acids, glycogen, or triglycerides GluT transporters bring glucose into the cell via facilitate diffusion  Insulin causes insertion of more of these transporters, increasing rate of entry into cells  Glucose trapped in cells after being phosphorylated

7. Copyright 2009, John Wiley & Sons, Inc. Glucose catabolism / cellular respiration 1. Glycolysis Anaerobic respiration – does not require oxygen 2. Formation of acetyl coenzyme A 3. Krebs cycle reactions 4. Electron transport chain reactions Aerobic respiration – requires oxygen

8. Copyright 2009, John Wiley & Sons, Inc. Overview of cellular respiration

9. 1 NADH+ 2 H + GLYCOLYSIS 2 2 2 Pyruvic acid 1 Glucose ATP 1 NADH+ 2 H + GLYCOLYSIS + 2 H + NADH CO 2 FORMATION OF ACETYL COENZYME A 2 2 2 2 2 Acetyl coenzyme A 2 Pyruvic acid 1 Glucose ATP 2 1 NADH+ 2 H + GLYCOLYSIS + 2 H + NADH CO 2 FORMATION OF ACETYL COENZYME A KREBS CYCLE + 6 H + CO 2 FADH 2 NADH 2 4 6 2 2 2 2 2 2 Acetyl coenzyme A 2 Pyruvic acid 1 Glucose ATP 2 3 1 NADH+ 2 H + GLYCOLYSIS + 2 H + NADH CO 2 FORMATION OF ACETYL COENZYME A KREBS CYCLE + 6 H + CO 2 FADH 2 NADH 2 4 6 2 ELECTRON TRANSPORT CHAIN e–e– e–e– e–e– 32 or 34 O2O2 6 6 2 2 2 2 H2OH2O Electrons 2 Acetyl coenzyme A 2 Pyruvic acid 1 Glucose ATP 2 3 4

10. Copyright 2009, John Wiley & Sons, Inc. Glycolysis 1. Glycolysis  Splits 6-carbon glucose into 2 3-carbon molecules of pyruvic acid  Consumes 2 ATP but generates 4  10 reactions  Fate of pyruvic acid depends on oxygen availability If oxygen is scarce (anaerobic), reduced to lactic acid  Hepatocytes can convert it back to pyruvic acid If oxygen is plentiful (aerobic), converted to acetyl coenzyme A

11. Copyright 2009, John Wiley & Sons, Inc. Cellular respiration begins with glycolysis

12. Copyright 2009, John Wiley & Sons, Inc. The 10 reactions of glycolysis

13. ADP O Glucose (1 molecule) CH 2 OH OH 41 32 5 6 ATP HH H H HO 1 H ADP O Glucose (1 molecule) CH 2 OH OH 41 32 5 6 Glucose 6-phosphate O OH OH 2 C P ATP H HO H H HH H H H 1 2 H H Phosphofructokinase ADP O Glucose (1 molecule) CH 2 OH OH 41 32 5 6 Glucose 6-phosphate O OH CH 2 OH Fructose 6-phosphate O OH H OH 2 C 6 5 4 3 2 1 ADP P OH 2 C P ATP OH H HO H H HH H H H H H 1 2 3 H H Phosphofructokinase ADP O Glucose (1 molecule) CH 2 OH OH 41 32 5 6 Glucose 6-phosphate O OH CH 2 OH Fructose 6-phosphate O OH H OH 2 C 6 5 4 3 2 1 CH 2 O Fructose 1, 6-bisphosphate O OH H OH 2 C ADP P P P OH 2 C P ATP OH H HO H H HH H H H H H H H OH 1 2 3 4 H H Phosphofructokinase Dihydroxyacetone phosphate CH 2 OH CH 2 O CO Glyceraldehyde 3-phosphate HCOH CH 2 O O HCHC ADP O Glucose (1 molecule) CH 2 OH OH 41 32 5 6 Glucose 6-phosphate O OH CH 2 OH Fructose 6-phosphate O OH H OH 2 C 6 5 4 3 2 1 CH 2 O Fructose 1, 6-bisphosphate O OH H OH 2 C ADP P P P P P OH 2 C P ATP OH H HO H H HH H H H H H H H OH 1 2 3 4 5 H H + 2H + NADH HCOH C CH 2 O O O 1, 3-Bisphosphoglyceric acid (2 molecules) 2 P P Phosphofructokinase Dihydroxyacetone phosphate CH 2 OH CH 2 O CO Glyceraldehyde 3-phosphate HCOH CH 2 O O HCHC ADP O Glucose (1 molecule) CH 2 OH OH 41 32 5 6 Glucose 6-phosphate O OH CH 2 OH Fructose 6-phosphate O OH H OH 2 C 6 5 4 3 2 1 CH 2 O Fructose 1, 6-bisphosphate O OH H OH 2 C ADP P P P P P OH 2 C P ATP OH H HO H H HH H H H H H H H OH 1 2 3 4 5 6 H H 2 NAD + + 2P

14. Copyright 2009, John Wiley & Sons, Inc. Formation of Acetyl coenzyme A 2. Formation of Acetyl coenzyme A  Each pyruvic acid converted to 2-carbon acetyl group Remove one molecule of CO 2 as a waste product  Each pyruvic acid also loses 2 hydrogen atoms NAD + reduced to NADH + H +  Acetyl group attached to coenzyme A to form acetyl coenzyme A (acetyl CoA)

15. Copyright 2009, John Wiley & Sons, Inc. Fate of pyruvic acid

16. Copyright 2009, John Wiley & Sons, Inc. The Krebs cycle 3. The Krebs cycle  Also known as citric acid cycle  Occurs in matrix of mitochondria  Series of redox reactions  2 decarboxylation reactions release CO 2  Reduced coenzymes (NADH and FADH 2 ) are the most important outcome  One molecule of ATP generated by substrate- level phosphorylation

17. Copyright 2009, John Wiley & Sons, Inc. The Krebs Cycle

18. Copyright 2009, John Wiley & Sons, Inc. The Eight reactions of the Krebs cycle

19. 1 C CH 2 COOH O Oxaloacetic acid COOH Citric acid H2CH2CCOOH HOC H2CH2CCOOH + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain H2OH2O CO 2 NAD + KREBS CYCLE NADH CoA 1 C CH 2 COOH O Oxaloacetic acid COOH Isocitric acid H2CH2CCOOH HOCCOOH HCCOOH H Citric acid H2CH2CCOOH HOC H2CH2CCOOH + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain H2OH2O CO 2 NAD + KREBS CYCLE NADH CoA 2 1 To electron transport chain CO 2 + H + C CH 2 COOH O Oxaloacetic acid COOH Alpha-ketoglutaric acid H2CH2CCOOH HCH CCOOH Isocitric acid H2CH2CCOOH HOCCOOH HCCOOH H Citric acid H2CH2CCOOH HOC H2CH2CCOOH NAD + + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain H2OH2O CO 2 NAD + KREBS CYCLE NADH CoA 2 3 O 1 To electron transport chain CO 2 + H + NADH CO 2 + H + C CH 2 COOH O Oxaloacetic acid COOH Succinyl CoA H2CH2CCOOH CH 2 CS CoA Alpha-ketoglutaric acid H2CH2CCOOH HCH CCOOH Isocitric acid H2CH2CCOOH HOCCOOH HCCOOH H Citric acid H2CH2CCOOH HOC H2CH2CCOOH NAD + + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain H2OH2O CO 2 NAD + KREBS CYCLE NADH O CoA O 2 3 4 1 To electron transport chain CO 2 + H + NADH CO 2 + H + C CH 2 COOH O Oxaloacetic acid COOH H2CH2C H2CH2C Succinic acid Succinyl CoA H2CH2CCOOH CH 2 CS CoA Alpha-ketoglutaric acid H2CH2CCOOH HCH CCOOH Isocitric acid H2CH2CCOOH HOCCOOH HCCOOH H Citric acid H2CH2CCOOH HOC H2CH2CCOOH NAD + GDP + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain ADP H2OH2O CO 2 NAD + KREBS CYCLE NADH ATP GTP O CoA O 2 3 4 5 1 To electron transport chain CO 2 + H + NADH CO 2 + H + To electron transport chain C CH 2 COOH O Oxaloacetic acid COOH H2CH2C H2CH2C Succinic acid Succinyl CoA H2CH2CCOOH CH 2 CS CoA Alpha-ketoglutaric acid H2CH2CCOOH HCH CCOOH Isocitric acid H2CH2CCOOH HOCCOOH HCCOOH H Citric acid H2CH2CCOOH HOC H2CH2CCOOH Fumaric acid NAD + GDP FAD HC CH + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain ADP FADH 2 COOH H2OH2O CO 2 NAD + KREBS CYCLE NADH ATP GTP CoA O 2 3 4 5 6 O 1 To electron transport chain CO 2 + H + NADH CO 2 + H + To electron transport chain C CH 2 COOH O Oxaloacetic acid COOH HCOH CH 2 COOH H2CH2C H2CH2C Succinic acid Malic acid Succinyl CoA H2CH2CCOOH CH 2 CS CoA Alpha-ketoglutaric acid H2CH2CCOOH HCH CCOOH Isocitric acid H2CH2CCOOH HOCCOOH HCCOOH H Citric acid H2CH2CCOOH HOC H2CH2CCOOH Fumaric acid NAD + GDP FAD HC CH + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain ADP FADH 2 COOH H2OH2O H2OH2O CO 2 NAD + KREBS CYCLE NADH ATP GTP CoA O 2 3 4 5 6 7 O 1 To electron transport chain CO 2 + H + NADH CO 2 + H + To electron transport chain C CH 2 COOH O Oxaloacetic acid COOH + H + NADH HCOH CH 2 COOH H2CH2C H2CH2C Succinic acid Malic acid Succinyl CoA H2CH2CCOOH CH 2 CS CoA Alpha-ketoglutaric acid H2CH2CCOOH HCH CCOOH Isocitric acid H2CH2CCOOH HOCCOOH HCCOOH H Citric acid H2CH2CCOOH HOC H2CH2CCOOH Fumaric acid NAD + GDP FAD NAD + HC CH + H + Pyruvic acid Acetyl coenzyme A C CH 3 O C COOH O To electron transport chain ADP FADH 2 COOH H2OH2O H2OH2O CO 2 NAD + KREBS CYCLE NADH ATP GTP CoA O 2 3 4 5 6 7 8 O

20. Copyright 2009, John Wiley & Sons, Inc. Electron transport chain 4. Electron transport chain  Series of electron carriers in inner mitochondrial membrane reduced and oxidized  As electrons pass through chain, exergonic reactions release energy used to form ATP Chemiosmosis  Final electron acceptor is oxygen to form water

21. Copyright 2009, John Wiley & Sons, Inc. Chemiosmosis  Carriers act as proton pumps to expel H + from mitochondrial matrix  Creates H + electrochemical gradient – concentration gradient and electrical gradient  Gradient has potential energy – proton motive force  As H + flows back into matrix through membrane, generates ATP using ATP synthase

22. Energy from NADH + H + H+H+ Low H + concentration in matrix of mitochondrion Inner mitochondrial membrane Matrix High H + concentration between inner and outer mitochondrial membranes Outer membrane Inner membrane H + channel Electron transport chain (includes proton pumps) 1 Energy from NADH + H + H+H+ H+H+ Low H + concentration in matrix of mitochondrion Inner mitochondrial membrane Matrix High H + concentration between inner and outer mitochondrial membranes Outer membrane Inner membrane H + channel Electron transport chain (includes proton pumps) 1 2 Energy from NADH + H + H+H+ H+H+ ADP + ATP synthase Low H + concentration in matrix of mitochondrion Inner mitochondrial membrane Matrix High H + concentration between inner and outer mitochondrial membranes Outer membrane Inner membrane H + channel Electron transport chain (includes proton pumps) P ATP 1 2 3

23. Copyright 2009, John Wiley & Sons, Inc. The actions of the three proton pumps and ATP synthase in the inner membrane of mitochondria Space between outer and inner mitochondrial membranes Inner mito- chondrial membrane Mitochondrial matrix H + channel NADH dehydrogenase complex: FMN and five Fe-S centers NAD e–e– H+H+ +++++++ ––– –––– Q NADH + H + 1 Space between outer and inner mitochondrial membranes Inner mito- chondrial membrane Mitochondrial matrix H + channel NADH dehydrogenase complex: FMN and five Fe-S centers Cytochrome b-c 1 complex: cyt b, cyt c 1, and an Fe-S center NAD e–e– e–e– e–e– H+H+ +++++++ ––– –––– Q Cyt c NADH + H + H + 12 Space between outer and inner mitochondrial membranes Inner mito- chondrial membrane Mitochondrial matrix H + channel NADH dehydrogenase complex: FMN and five Fe-S centers Cytochrome b-c 1 complex: cyt b, cyt c 1, and an Fe-S center Cytochrome oxidase complex: cyt a, cyt a 3,and two Cu NAD 1 1/2 O2O2 e–e– e–e– e–e– e–e– e–e– H+H+ H+H+ H+H+ +++++++ ––– –––– H2OH2O Q Cyt c NADH + H + H + 3 ADP + ATP synthase P ATP 123 3

24. Copyright 2009, John Wiley & Sons, Inc. Summary of cellular respiration

25. Copyright 2009, John Wiley & Sons, Inc. Glucose anabolism  Glucose storage: glycogenesis Polysaccharide that is the only stored carbohydrate in humans Insulin stimulates hepatocytes and skeletal muscle cells to synthesize glycogen  Glucose release: glycogenolysis Glycogen stored in hepatocytes broken down into glucose and release into blood

26. Copyright 2009, John Wiley & Sons, Inc. Glycogenesis and glycogenolysis

27. Copyright 2009, John Wiley & Sons, Inc. Formation of glucose from proteins and fats: gluconeogenesis Glycerol part of triglycerides, lactic acid, and certain amino acids can be converted by the liver into glucose Glucose formed from noncarbohydrate sources Stimulated by cortisol and glucagon

28. Copyright 2009, John Wiley & Sons, Inc. Lipid metabolism Transport by lipoproteins  Most lipids nonpolar and hydrophobic  Made more water-soluble by combining them with proteins to form lipoproteins  Proteins in outer shell called apoproteins (apo) Each has specific functions All essentially are transport vehicles

29. Copyright 2009, John Wiley & Sons, Inc. Apoproteins Apoproteins categorized and named according to density (ratio of lipids to proteins)  Chylomicrons Form in small intestine mucosal epithelial cells Transport dietary lipids to adipose tissue  Very low-density lipoproteins (VLDLs) Form in hepatocytes Transport endogenous lipids to adipocytes  Low-density lipoproteins (LDLs) – “bad” cholesterol Carry 75% of total cholesterol in blood Deliver to body cells for repair and synthesis Can deposit cholesterol in fatty plaques  High-density lipoproteins (HDLs) – “good” cholesterol Remove excess cholesterol from body cells and blood Deliver to liver for elimination

30. Copyright 2009, John Wiley & Sons, Inc. Lipid Metabolism 2 sources of cholesterol in the body  Present in foods  Synthesized by hepatocytes As total blood cholesterol increases, risk of coronary artery disease begins to rise  Treated with exercise, diet, and drugs Lipids can be oxidized to provide ATP  Stored in adipose tissue if not needed for ATP Major function of adipose tissue to remove triglycerides from chylomicrons and VLDLs and store it until needed  98% of all body energy reserves

31. Copyright 2009, John Wiley & Sons, Inc. Lipid Metabolism Lipid catabolism: lipolysis  Triglycerides split into glycerol and fatty acids  Must be done for muscle, liver, and adipose tissue to oxidize fatty acids  Enhanced by epinephrine and norepinephrine Lipid anabolism: lipogenesis  Liver cells and adipose cells synthesize lipids from glucose or amino acids  Occurs when more calories are consumed than needed for ATP production

32. Copyright 2009, John Wiley & Sons, Inc. Pathways of lipid metabolism

33. Copyright 2009, John Wiley & Sons, Inc. Protein metabolism Amino acids are either oxidized to produce ATP or used to synthesize new proteins Excess dietary amino acids are not excreted but converted into glucose (gluconeogenesis) or triglycerides (lipogenesis) Protein catabolism  Proteins from worn out cells broken down into amino acids  Before entering Krebs cycle amino group must be removed – deamination Produces ammonia, liver cells convert to urea, excreted in urine

34. Copyright 2009, John Wiley & Sons, Inc. Various points at which amino acids enter the Krebs cycle for oxidation

35. Copyright 2009, John Wiley & Sons, Inc. Protein anabolism  Carried out in ribosomes of almost every cell in the body  10 essential amino acids in the human Must be present in the diet because they cannot be synthesized Complete protein – contains sufficient amounts of all essential amino acids – beef, fish, poultry, eggs Incomplete protein – does not – leafy green vegetables, legumes, grains  10 other nonessential amino acids can be synthesized by body cells using transamination  http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm

36. Copyright 2009, John Wiley & Sons, Inc. Key molecules at metabolic crossroads 3 molecules play pivotal roles in metabolism Stand at metabolic crossroads – reactions that occur or not depend on nutritional or activity status of individual 1. Glucose 6-phosphate  Made shortly after glucose enters body cell  4 fates – synthesis of glycogen, release of glucose into blood stream, synthesis of nucleic acids, glycolysis

37. Copyright 2009, John Wiley & Sons, Inc. Key molecules at metabolic crossroads 2. Pyruvic acid  If there is enough oxygen, aerobic cellular respiration occurs  If there is not enough oxygen, anaerobic reactions can produce lactic acid, gluconeogenesis 3. Acetyl Coenzyme A  When ATP is low and oxygen plentiful, most pyruvic acid goes to ATP production via Acetyl CoA  Acetyl CoA is at the entry into the Krebs cycle  Can also be used for synthesis of certain lipids

38. Copyright 2009, John Wiley & Sons, Inc. Metabolic adaptations During the absorptive state ingested nutrients are entering the blood stream  Glucose readily available for ATP production During postabsorptive state absorption of nutrients from GI tract complete  Energy needs must be met by fuels in the body  Nervous system and red blood cells depend on glucose so maintaining steady blood glucose critical

39. Copyright 2009, John Wiley & Sons, Inc. Metabolism during absorptive state  Soon after a meal nutrients enter blood Glucose, amino acids, and triglycerides in chylomicrons  2 metabolic hallmarks Oxidation of glucose for ATP production in all body cells Storage of excess fuel molecules in hepatocytes, adipocytes, and skeletal muscle cells  Pancreatic beta cells release insulin Promotes entry of glucose and amino acids into cells

40. Copyright 2009, John Wiley & Sons, Inc. Principal metabolic pathways during the absorptive state

41. AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT + H 2 O +CO 2 MOST TISSUES Oxidation ATP 1 AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT HEPATOCYTES IN LIVER + H 2 O +CO 2 MOST TISSUES Oxidation ATP Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glycogen Glucose + H 2 O +CO 2 ATP 1 2 AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT HEPATOCYTES IN LIVER + H 2 O +CO 2 MOST TISSUES Oxidation ATP Triglycerides ADIPOSE TISSUE VLDLs Triglycerides Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glycogen Glucose + H 2 O +CO 2 ATP 1 2 3 AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT GLUCOSE HEPATOCYTES IN LIVER SKELETAL MUSCLE Storage + H 2 O +CO 2 MOST TISSUES Oxidation ATP Triglycerides ADIPOSE TISSUE VLDLs Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glucose Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glycogen Glucose Glycogen + H 2 O +CO 2 ATP 1 2 3 4 4 AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT GLUCOSE HEPATOCYTES IN LIVER SKELETAL MUSCLE Storage + H 2 O +CO 2 MOST TISSUES Oxidation ATP Triglycerides ADIPOSE TISSUE VLDLs Triglycerides Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glucose Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glycogen Glucose Glycogen + H 2 O +CO 2 ATP 1 2 3 45 4 AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT GLUCOSE HEPATOCYTES IN LIVER SKELETAL MUSCLE Storage + H 2 O +CO 2 MOST TISSUES Oxidation ATP Triglycerides ADIPOSE TISSUE VLDLs Triglycerides Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glucose Keto acids Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glycogen Glucose Glycogen + H 2 O +CO 2 ATP 1 2 3 45 6 4 AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT GLUCOSE HEPATOCYTES IN LIVER SKELETAL MUSCLE Storage + H 2 O +CO 2 MOST TISSUES Oxidation ATP Triglycerides ADIPOSE TISSUE VLDLs Triglycerides Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glucose Keto acids Fatty acids Proteins Triglycerides Glyceraldehyde 3-phosphate Glycogen Glucose Glycogen + H 2 O +CO 2 ATP 1 2 3 45 6 7 4 AMINO ACIDSGLUCOSE TRIGLYCERIDES (in chylomicrons) Blood GLUCOSE GASTROINTESTINAL TRACT GLUCOSE HEPATOCYTES IN LIVER SKELETAL MUSCLE Storage + H 2 O +CO 2 MOST TISSUES Oxidation ATP Triglycerides ADIPOSE TISSUE VLDLs Triglycerides Fatty acids Triglycerides Glyceraldehyde 3-phosphate Glucose Keto acids Fatty acids Proteins Triglycerides Glyceraldehyde 3-phosphate Glycogen Glucose Glycogen Proteins + H 2 O +CO 2 ATP 1 2 3 45 6 7 8 4

42. Copyright 2009, John Wiley & Sons, Inc. Metabolism during postabsorptive state  About 4 hours after the last meal absorption in small intestine nearly complete  Blood glucose levels start to fall  Main metabolic challenge to maintain normal blood glucose levels  Glucose production Breakdown of liver glycogen, lipolysis, gluconeogenesis using lactic acid and/or amino acids  Glucose conservation Oxidation of fatty acids, lactic acid, amino acids, ketone bodies (used by heart, kidneys, etc for ATP prodution) and breakdown of muscle glycogen

43. Copyright 2009, John Wiley & Sons, Inc. Principal metabolic pathways during the postabsorptive state

44. 1 Liver glycogen Glucose LIVER Blood HEARTADIPOSE TISSUE SKELETAL MUSCLE TISSUE OTHER TISSUES 1 Liver glycogen Glucose LIVER Glycerol Blood HEART Fatty acids Glycerol Triglycerides ADIPOSE TISSUE SKELETAL MUSCLE TISSUE OTHER TISSUES 2 Fatty acids 1 Liver glycogen Glucose LIVER Lactic acid Glycerol Blood HEART Fatty acids Glycerol Triglycerides ADIPOSE TISSUE SKELETAL MUSCLE TISSUE OTHER TISSUES 3 2 Fatty acids 1 Liver glycogen Keto acids Glucose Amino acids LIVER Lactic acid Glycerol Blood HEART Muscle proteins Fatty acids Glycerol Triglycerides ADIPOSE TISSUE Fasting or starvation SKELETAL MUSCLE TISSUE OTHER TISSUES Proteins Amino acids 4 4 3 4 2 Fatty acids 1 Liver glycogen Keto acids Glucose Amino acids LIVER Lactic acid Glycerol Blood HEART Fatty acids Muscle proteins Fatty acids Glycerol Triglycerides ADIPOSE TISSUE Fasting or starvation SKELETAL MUSCLE TISSUE OTHER TISSUES Fatty acids Proteins Amino acids Fatty acids ATP 4 5 5 4 3 5 4 2 Fatty acids 1 Liver glycogen Keto acids Glucose Amino acids LIVER Lactic acid Glycerol Blood HEART Fatty acids Muscle proteins Fatty acids Glycerol Triglycerides ADIPOSE TISSUE Fasting or starvation SKELETAL MUSCLE TISSUE OTHER TISSUES Fatty acids Proteins Amino acids Fatty acids Lactic acid ATP 4 5 5 6 4 3 5 4 2 Fatty acids 1 Liver glycogen Keto acids Glucose Amino acids LIVER Lactic acid Glycerol Blood HEART Fatty acids Muscle proteins Fatty acids Glycerol Triglycerides ADIPOSE TISSUE Fasting or starvation SKELETAL MUSCLE TISSUE OTHER TISSUES Fatty acids Proteins Amino acids Fatty acids Lactic acid ATP 4 5 5 6 7 4 3 5 4 2 Fatty acids 1 Liver glycogen Keto acids Glucose Amino acids LIVER Fatty acids Lactic acid Ketone bodies Glycerol Blood NERVOUS TISSUE Ketone bodies Glucose Starvation HEART Fatty acids Muscle proteins Fatty acids Glycerol Triglycerides ADIPOSE TISSUE Fasting or starvation SKELETAL MUSCLE TISSUE Ketone bodies OTHER TISSUES Fatty acids Proteins Amino acids Fatty acids Ketone bodies Lactic acid ATP 4 5 8 5 6 8 8 7 4 3 5 4 2 8 1 Liver glycogen Keto acids Glucose Amino acids LIVER Fatty acids Lactic acid Ketone bodies Glycerol Blood NERVOUS TISSUE Ketone bodies Glucose Starvation HEART Fatty acids Muscle proteins Fatty acids Glycerol Triglycerides ADIPOSE TISSUE Fasting or starvation SKELETAL MUSCLE TISSUE Ketone bodies OTHER TISSUES Fatty acids Proteins Amino acids Glucose 6-phosphate Pyruvic acid Lactic acid Muscle glycogen (aerobic)(anaerobic) Amino acids Fatty acids Ketone bodies Lactic acid ATP O2O2 +O2O2 – 4 5 8 5 6 8 8 7 4 3 9 5 4 2 8

45. Copyright 2009, John Wiley & Sons, Inc. Hormones and autonomic nervous system regulate metabolism during postabsorptive state  As blood glucose decline, insulin secretion falls Glucagon – increases release of glucose into blood via gluconeogenesis and glycogenolysis  Sympathetic nerve endings of ANS release norepinephrine and adrenal medulla releases epinephrine and norepinephrine Stimulate lipolysis, glycogen breakdown

46. Copyright 2009, John Wiley & Sons, Inc. Heat and energy balance Heat – form of energy that can be measured as temperature and can be expressed in calories  calorie (cal) – amount of heat required to raise 1 gram of water 1°C  Kilocalorie (kcal) or Calorie (Cal) is 1000 calories Metabolic rate – overall rate at which metabolic reactions use energy  Some energy used to make ATP, some lost as heat  Basal metabolic rate (BMR) – measurement with body in quiet, resting, fasting condition

47. Copyright 2009, John Wiley & Sons, Inc. Body temperature homeostasis  Despite wide fluctuations in environmental temperatures, homeostatic mechanisms maintain normal range for internal body temperature  Core temperature (37°C or 98.6°F) versus shell temperature (1-6°C lower)  Heat produced by exercise, some hormones, sympathetic nervous system, fever, ingestion of food, younger age, etc.

48. Copyright 2009, John Wiley & Sons, Inc. Heat and engery balance Heat can be lost through  Conduction to solid materials in contact with body  Convection – transfer of heat by movement of a gas or liquid  Radiation – transfer of heat in form of infrared rays  Evaporation exhaled air and skin surface (insensible water loss) Hypothalamic thermostat in preoptic area  Heat-losing center and heat-promoting center

49. Copyright 2009, John Wiley & Sons, Inc. Thermoregulation If core temperature declines  Skin blood vessels constrict  Release of thyroid hormones, epinephrine and norepinephrine increases cellular metabolism  Shivering If core body temperature too high  Dilation of skin blood vessels  Decrease metabolic rate  Stimulate sweat glands

50. Copyright 2009, John Wiley & Sons, Inc. Negative feedback mechanisms that conserve heat and increase increase production

51. Copyright 2009, John Wiley & Sons, Inc. Nutrition Nutrients are chemical substances in food that body cells use for growth, maintenance, and repair 6 main types 1. Water – needed in largest amount 2. Carbohydrates 3. Lipids 4. Proteins 5. Minerals 6. Vitamins Essential nutrients must be obtained from the diet

52. Copyright 2009, John Wiley & Sons, Inc. Guidelines for healthy eating  We do not know with certainty what levels and types of carbohydrates, fat and protein are optimal  Different populations around the world eat radically different diets adapted to their particular lifestyle  Basic guidelines Eat a variety of foods Maintain a healthy weight Choose foods low in fat, saturated fat and cholesterol Eat plenty of vegetables, fruits and grain products Use sugars in moderation only

53. Copyright 2009, John Wiley & Sons, Inc. MyPyramid

54. Copyright 2009, John Wiley & Sons, Inc. Minerals  Inorganic elements that occur naturally in Earth’s crust  Eat foods that contain enough calcium, phosphorus, iron and iodine  Excess amounts of most minerals are excreted in urine and feces  Major role of minerals to help regulate enzymatic reactions

57. Copyright 2009, John Wiley & Sons, Inc. Vitamins  Organic nutrients required in small amounts to maintain growth and normal metabolism  Do not provide energy or serve as body’s building materials  Most are coenzymes  Most cannot be synthesized by the body  Vitamin K produced by bacteria in GI tract  No single food contains all the required vitamins  2 groups Fat-soluble – A, D, E, K Water-soluble – several B vitamins and vitamin C