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Digestion lab

Experiment #1: Carbohydrate Digestion – Tube 1 Digestion Lab — 3 ml water – Tube 2 — 3 ml 0. 2% amylase – Tube 3 — 3 ml 0. 2% amylase + 10 drops of 1. 0M HCl – Tube 4 1 2 4 3 — 3 ml 0. 2% amylase — place in hot water bath for 5 min Experiment #1: Carbohydrate Digestion – Add 5. 0 ml starch solution to each tube – Incubate in 37°C bath for 1. 5 hr – Divide contents of each tube evenly into 2 tubes — Lugol’s Test — Benedict’s Test Experiment #1: Carbohydrate Digestion – Lugol’s Test — presence of starch 2 1 1 2 3 4 – add a few drops of Lugol’s reagent (iodine) 4 3 1 2 3 4 Experiment #1: Carbohydrate Digestion blue = – (none) green = + (a little bit) yellow = ++ (some) orange = +++ (lots) 3 4 or – Add egg white into each tube – Tube 1 — presence of maltose — — — — 2 Experiment #2: Protein Digestion – Benedict’s Test – add 5. 0 ml of Benedict’s reagent – immerse in hot water bath for 2 min – rate the amt of maltose present 1 — if starch absent, transparent brown color — if starch present, opaque black-blue color — 10 drops of water + 5. 0 ml pepsin – Tube 2 — 10 drops of 1M HCl + 5. 0 ml pepsin 1 2 3 4 – Tube 3 — 10 drops of 1M HCl + 5. 0 ml pepsin — place in ice bath 1 2 3 4 5 – Tube 4 — 10 drops of 1M HCl + 5. 0 ml water – Tube 5 — 10 drops of 1M NaOH + 5. 0 ml pepsin 1 Experiment #2: Protein Digestion Experiment #3: Fat Digestion – add 3. 0 ml of cream to each tube – Tube 1 – Incubate tubes 1, 2, 4 and 5 at 37 C for 1. 5 hours – Observe any digestion of egg white — 5. 0 ml water + few grains of bile salts – Tube 2 — 5. 0 ml pancreatin – Tube 3 undigested — 5. 0 ml pancreatin + few grains of bile salts digested Experiment #3: Fat Digestion – Test pH of each solution w/ pH probe — rinse probe w/ detergent after each test – Place in 37°C bath – Retest pH at 20, 40 and 60 min Enzymes Protein Catalysts – speed up the rate of chemical reactions – are not permanently altered in the reactions – do not change the nature of the reaction Digestion – Physical and chemical break down nutrients into absorbable unit 1. Physical digestion (chewing, mixing) 2. Chemical digestion (enzyme catalyzed) – – – polysaccharides → monosaccharides proteins → amino acids fats → glycerol + fatty acids Factors Affecting Enzyme Activity – Temperature — ↑ Temp, ↑ kinetic energy, ↑ reaction rate — high Temp changes structure of enzymes – ↓’s enzyme function 2 Factors Affecting Enzyme Activity – pH — 3D structure of enzymes changes at different pH — optimal enzyme function at specific pH — ↓ function at higher or lower pH’s Oxidation-Reduction Reactions Carbohydrate Digestion – begins with salivary amylase (ptyalin) – breaks starch (polysaccharide) into maltose (disaccharide) – Simple sugars = reducing sugars — Drive reduction reactions for other substances — Become oxidized Benedict’s Test – oxidation reaction — reaction in which a molecule loses e-s – reduction reaction — reaction in which a molecule gains e-s – Example — NADH → NAD+ = oxidation — NAD+ → NADH = reduction — O2 + 4H+ + 4e- → 2H2O = reduction Protein Digestion – Begins in the stomach – Gastric Epithelial Cells — Parietal Cells – Secrete HCl — Chief Cells – Secrete Pepsinogen – Low pH activates pepsinogen – Pepsinogen autocatalyzes self into pepsin – Cleaves proteins – Cu2+ + Maltose (reduced) → Cu+ + Maltose (oxidized) – 4 Cu+ + O2 → Cu2O (orange color) Protein Digestion – Continues in small intestine — chyme enters pyloric sphincter — intestine releases hormone (secretin), that stimulates the release of pancreatic juices — Chymotrypsin, trypsin, etc. – Enzymes activated in intestine – Digest small polypeptides into amino acids 3 Fat Digestion – Begins in stomach – Most in small intestine — (pancreatic and intestinal lipases) – Fats are nonpolar! – Digestion depends on the presence of bile from the gall bladder — emulsification breaks up fat into small droplets – lipases break triglycerides into monoglycerides + fatty acids – form micelles in intestinal lumen Fat Digestion – absorbed by the epithelium – reform triglycerides in the epithelial cells – combined w/ protein to form chylomicrons which are secreted into lacteals – carried via lymph to the veins Fat Digestion – Triglycerides → glycerol + fatty acids – Fatty acids lower pH of aqueous solutions — ↑ fat digestion, ↓ pH 4

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