Are you healthy?

What are humans supposed to eat?

What is a “Diet”?

Government suggested Diet

© 2014 Pearson Education, Inc. Stage 1 Digestion in GI tract lumen to absorbable forms. Transport via blood to tissue cells. Stage 2 Anabolism (incorporation into molecules) and catabolism of nutrients to form intermediates within tissue cells. Stage 3 Oxidative breakdown of stage 2 products occurs in mitochondria of tissue cells. CO 2 is liberated, and H atoms removed are ultimately delivered to molecular oxygen, forming water. Some energy released is used to form ATP. Catabolic reactions Anabolic reactions PROTEINS Amino acids Proteins Infrequent CARBOHYDRATES Glucose and other sugars Glucose Glycolysis Pyruvic acid Krebs cycle Acetyl CoA Oxidative phosphorylation (in electron transport chain) Glycogen Glycerol Fatty acids Fats FATS Figure 23.3 Three stages of metabolism of energy-containing nutrients.

C 6 H 12 O 6 represents glucose, galactose, fructose

© 2014 Pearson Education, Inc. The Na + -K + pump stores energy that drives glucose (and galactose) uptake by creating a steep concentration gradient for Na + entry into intestinal cells. As Na + moves across the membrane through a membrane cotransporter protein (in this case SGLT), it drives glucose against its concentration gradient into the cells. Fructose enters the cell by facilitated diffusion. All three monosaccharides exit across the basolateral membrane via facilitated diffusion on the GLUT2 sugar transporter. Na + -glucose symport transporter GlucoseGalactose Fructose Facilitated diffusion transporter Brush border of intestinal cell GLUT2 Capillary Na + -K + pump 1 Na K+K+ Figure Absorption of monosaccharides.

© 2014 Pearson Education, Inc. Figure Interconversion of carbohydrates, fats, and proteins. Proteins Amino acids Urea Excreted in urine Carbohydrates Glycogen Glucose Glucose-6-phosphate Glyceraldehyde 3-phosphate Pyruvic acid Acetyl CoA Krebs cycle Fats Triglycerides (neutral fats) Glycerol and fatty acids Lactic acid Ketone bodies Keto acids

Mono Unsaturated Fats Omega-6 Poly Unsaturated Fats Omega-3 Poly Unsaturated Fats Avocado OilSoybean OilCold Water Fish Olive OilCorn OilFlax Seed Oil

Consequences of protein deficiency?

© 2014 Pearson Education, Inc. Figure Interconversion of carbohydrates, fats, and proteins. Proteins Amino acids Urea Excreted in urine Carbohydrates Glycogen Glucose Glucose-6-phosphate Glyceraldehyde 3-phosphate Pyruvic acid Acetyl CoA Krebs cycle Fats Triglycerides (neutral fats) Glycerol and fatty acids Lactic acid Ketone bodies Keto acids

© 2014 Pearson Education, Inc. Figure Interconversion of carbohydrates, fats, and proteins. Proteins Amino acids Urea Excreted in urine Carbohydrates Glycogen Glucose Glucose-6-phosphate Glyceraldehyde 3-phosphate Pyruvic acid Acetyl CoA Krebs cycle Fats Triglycerides (neutral fats) Glycerol and fatty acids Lactic acid Ketone bodies Keto acids

© 2014 Pearson Education, Inc. Lumen of intestine Pancreatic proteases Amino acids of protein fragments Brush border enzymes Na + Absorptive epithelial cell Apical membrane (microvilli) Amino acid carrier Capillary Proteins and protein fragments are digested to amino acids by pancreatic proteases (trypsin, chymotrypsin, and carboxy- peptidase), and by brush border enzymes (carboxypeptidase, aminopeptidase, and dipeptidase) of mucosal cells. The amino acids are then absorbed by active transport into the absorptive cells, and move to their opposite side. The amino acids leave the villus epithelial cell by facilitated diffusion and enter the capillary via intercellular clefts. Na + Figure Protein digestion and absorption in the small intestine

© 2014 Pearson Education, Inc. Glycolysis Krebs cycle Electron trans- port chain and oxidative phosphorylation Carbon atom Inorganic phosphate Coenzyme A Cytosol Mitochondrion (matrix) Transitional phase Oxaloacetic acid (pickup molecule) Malic acid Fumaric acid Succinic acid Pyruvic acid from glycolysis Krebs cycle Citric acid (initial reactant) Isocitric acid α -Ketoglutaric acid Succinyl-CoA Figure 23.7 Simplified version of the Krebs (citric acid) cycle.

Radical Oxygen (oxidants)!