Digestion & Reassembly Oh, YUCK! http://www.youtube.com/watch?v=Uzl6M1YlU3w

Animal Nutrition Why do we eat? 1 Why do we eat? We need matter and energy to grow, repair, and maintain our bodies: nutrients (E.g.: carbs, proteins, lipids, water…) Some nutrients cannot be made by our bodies from other materials, so we must get them through our food: Essential nutrients Essential amino acids Building the “ALABAMA” protein Essential fatty acids E.g., omega-3 and omega-6 fatty acids (found in fish and seeds) Vitamins E.g., vitamin A, B vitamins, vitamin C, Niacin, Folic acid Minerals E.g., calcium, phosphorus, sodium Folic acid and Vit C, E, Magnesium, Manganese – not in meat salt Chemical energy and biosynthesis Source of carbon and nitrogen Corn – no trytophan or lysine Vegan – B12, Cobalt (part of B12)

Mammalian Digestive System 2 Is the digestive tract inside or outside of the body? Does digestion happen inside or outside of our cells? Extracellular digestion – anything we want to keep, we have to bring INTO our cells. Fig. 41.10

Stages of Food Processing 3 Ingestion – eating Digestion – breaking down food into molecules small enough for the body to absorb Need to be able to pass into cells, and be in forms that the cells can use - use components Chemical and mechanical Absorption – small molecules taken up (absorbed by body) If no absorption, would loose it all Elimination – undigested food passes out of the digestive tract

The Mouth Mechanical digestion - chewing 5 The Mouth Mechanical digestion - chewing Chemical digestion - enzyme that hydrolyzes starch & glycogen Saliva – contains digestive enzymes, protects oral cavity Mucin - glycoprotein Digestion begins in oral cavity with mechanical breakdown of food Epiglottis important in preventing food from going down your trachea Buffers protect teeth from acidic materials Lysosyme – enzyme that attaches to and disables bacteria Starch broken down into smaller polysaccharides Butter digestion not begun yet

The Stomach Secretes acid and an enzyme HCL (hydrochloric acid) pH 2 6 Secretes acid and an enzyme HCL (hydrochloric acid) pH 2 Disrupts extracellular matrix of cells Kills most bacteria Denatures proteins enzyme breaks bond between amino acids (protein digesting enzyme) breaks the peptide bonds between amino acids Polysaccharides not broken down further Proteins in butter start to be broken down into smaller polypeptides

The Small Intestine - Digestion 8 Churning Nutrient-rich broth (chyme) enters small intestine Liver secretes bile – helps digestion of fats Pancreas secretes enzymes & chemicals that raise the pH Small intestine secretes enzymes Chyme leaves stomach 2-6 hours after a meal Churning mixes stomach contents Chyme moves on to small intestine Nutrient-rich broth (acidic) Regulated by sphincter The Duodenum (~first 25 cm) Trypsin, chymotrypsin (proteases) Pancreatic amylases, nucleases, lipases Digestion of polyacharides into monosaccharides Fat globules broken down into glycerol, fatty acids, monoglycerides Proteins broken down into amino acids Food now broken down into monosaccharides, amino acids, glycerol, fatty acids, nucleotides

The Small Intestine - Absorption 9 Nutrients transported across epithelial cells to bloodstream. Nutrients in bloodstream circulated to all cells in the body and transported across plasma membrane for use in the cell. Ileum and jejunum Villi – folds – increases surface area Surface rea 300 m2 (size of tennis court)

The Large Intestine Colon Rectum Recover water for the body 10 Colon Recover water for the body Rectum Stores feces (undigested material such as cellulose, and lots of intestinal bacteria!) http://en.wikipedia.org/wiki/Large_intestine

From food cells to our cells! 11 Starch to glycogen Proteins to (different) proteins Lipids to (different) lipids Polynucleotides to (different) polynucleotides From food cells to our cells! Starch (polysacchride broken down into glucose (monomer), transported in bloodstream to the liver and muscle cells, converted to glycogen in the cytoplasm of the cell with the assistance of glycogen synthase, an enzyme