1) break it down! -" hydrolysis " of complex molecules breaks 'em apart in the presence of H 2 O

1. ok, you've just eaten a bean burrito - how do you use it? 1) break it down! -"hydrolysis" of complex molecules breaks 'em apart in the presence of H2O - using enzymes 2) bring it in! - small compounds are taken up by cells ("absorbed") and used for energy, metabolism, body upkeep, etc., and to.... ...build complex molecules! Kangaroo Rat Dipodomys spectabilis http://www.nps.gov/whsa/anmlist_main.htm

2. a few words on enzymes (AKA "that molecule stuff is like a recurring nightmare") often named "____ase", with the "___" part being the substrate for the enzymatic reaction for example protease, lipase, amylase enzymes catalyze reactions (speed 'em up) enzymatic function influenced by: - temperature, other enzymes, heavy metals, pH

3. MAIN REGIONS OF THE DIGESTIVE SYSTEM REGION: FUNCTION: - saliva breaks down some starch; chewing Mouth Esophagus Stomach duodenum jejunum ileum Colon rectum & anus - transit; "peristalsis" - storage; pepsin digests some proteins; acid kills some bacteria - fat, protein and carbohydrate digestion & absorption - water and electrolyte transport (out of gut) - bile salt transport (out of gut) Small intestine - water and electrolyte transport (out of gut); storage of undigested material for... - defecation Large intestine Ted Burdyga, University of Liverpool

4. SECRETIONS OF (things that are released by) THE GUT Salivary glands - synthesis/secretion: amylase, mucus. Water, electrolytes Pancreas - synthesis/secretion: protease,lipase,amylase bicarbonate, water Stomach acid Pepsin Bicarbonate Bicarbonate Liver - bile salt synthesis, bile secretion. Gall bladder - storage and concentration of bile Ted Burdyga, University of Liverpool

5. DIGESTION OF PROTEINS broken down into amino acids, and then recycled in vertebrates, two famous hydrolytic enzymes: pepsin, trypsin problem: why don't the pepsins digest the organism's own proteins?? The inactive form (called "pepsinogen") is secreted from cells in stomach wall, then converted by acidic stomach environment into pepsin (active)

6. DIGESTION OF CARBOHYDRATES starches - amylase lactose, lactase and "lactose intolerance" disaccharides monosaccharides (for example, using "sucrase") in vertebrates, carbohydrates are important for brain function! cellulose (plant sugar) & cellulase (the enzyme that breaks it down) we don't have this enzyme, and neither do most critters remember termites and orangutans? Scott Bauer Ben van Wijnen

7. DIGESTION OF FATS 1 glycerol + 3 fatty acids "hydrolysis" of fats? emulsification (little droplets) using bile acids (liver, gall bladder) lipase can then catalyze (speed up) hydrolysis reaction some emulsified fat droplets can be taken up directly by the cells lining the gut

8. the brain-digestive connection Cholecystokinin (CCK) - a 33-amino acid protein (CCK-33) produced by special small intestinecells in response to food released into the bloodstream stimulates gall bladder contraction (release of bile) secretion of digestive enzymes into the pancreas brain has CCK receptors an enzyme cleaves off the end of CCK-33 produces CCK-8, which acts on brain to promote satiation (feeling full) genetically obese mice - low CCK-8 levels CCK-8 inhibits eating in stressed rats (opiates - morphine, endorphins - have similar effect) Kay Chernush

9. VITAMINS water soluble vitamins - include vitamin C and the B vitamins -carbohydrate metabolism, cellular metabolism, amino acid production, immune system function, blood cell production... fat soluble vitamins - include vitamins A,D,E and K -cell growth, eye sight, calcium uptake, nervous function, blood clotting...

10. ruminants sheep & cows: 2/3 body weight = water half of that water passes through saliva therefore 1/3 of body weight is saliva! methane production gut bacteria have cellulase (1/50 of cow's weight) http://www.hillstrath.on.ca/moffatt/bio3a/digestive/cowgut.htm