1. Digestion & Reassembly
Oh, YUCK!

2. 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)

3. Mammalian Digestive System2
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

4. Stages of Food Processing3
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

5. The Mouth Mechanical digestion - chewing5
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

6. The Stomach Secretes acid and an enzyme HCL (hydrochloric acid) pH 26
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

7. The Small Intestine - Digestion8
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

8. The Small Intestine - Absorption9
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)

9. The Large Intestine Colon Rectum Recover water for the body10
Colon
Recover water for the body
Rectum
Stores feces (undigested material such as cellulose, and lots of intestinal bacteria!)

10. 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