Digestion = hydrolysis reactions involving enzymes (enzymes = biological catalysts) -a specific enzyme acts on a specific substrate using water to break chemical bonds resulting in particular products -the specificity is based on the active site of the enzyme; a space in folded protein structure where the substrate will fit and bind -enzymes are usually named for their substrate and end in “-ase” BIO132 Lab 7: Exercise 39A/39 Chemical Processes of Digestion Cofactor

Starch digestion by amylase (amylase) Starch (amylose) + water > maltose Assay for enzyme (amylase) activity: Assay for starch: Lugol’s IKI + starch = blue/purple/black precipitate Assay for maltose: Benedict’s reagent + maltose = green, yellow, orange, red precipitate (green = less maltose, red = more) Figure 39A.1 / 39.1

Lipid emulsification by bile (mix) Fats and oils + bile > emulsified fats (tiny droplets suspended in water) allows easier access by water-soluble enzymes *NOT digestion!

Lipid digestion by lipase (pancreatic lipase) (pancreatic lipase) Triglycerides + water > glycerol + fatty acids Assay for enzyme (lipase) activity: Litmus cream = milk cream (triglycerides) + litmus pH indicator Neutral to alkaline pH litmus is purple to blue (cream is neutral) Acidic pH litmus is pink (assay for fatty acids which have acid pH) Figure 39A.1 / 39.1

Enzymes are biological catalysts, proteins that function to “speed up” chemical reactions by holding substrate in the active site. Enzymatic reactions can be impacted by environmental conditions: -Enzymes have optimal temperatures and pH for their activity. -Human digestive enzymes have an optimal temperature equal to body temperature (37°C). Most have an optimal pH around neutral (pH7) -If the temperature is too high, or pH is too acidic or basic, enzymes can be denatured and will no longer catalyze the reaction. -If the temperature is too low, enzymes will function slowly or not at all in the reaction. native conformation denatured

Salivary Amylase Digestion of Starch Tube no. Additives (3 gtt ea) 1A2A3A4A Boil amylase 4 min, then add starch 5A6A 0C0C37  C Incubation condition IKI test (color change) Positive (  ) or negative (  ) result Benedict’s test (color change) Positive (  ) or negative (  ) result Additive key:  Amylase  Starch  Maltose  Water Add acid

Salivary Amylase Digestion of Starch Tube no. Additives (3 gtt ea) 1A2A3A4A Boil amylase 4 min, then add starch 5A6A 0C0C37  C Incubation condition IKI test (color change) Positive (  ) or negative (  ) result Benedict’s test (color change) Positive (  ) or negative (  ) result Additive key:  Amylase  Starch  Maltose  Water black + - blue yellow - - blue yellow - + orange black + - blue yellow - + orange dark partial + yellowish partial + Add acid

Unnumbered Figure 39.3 Pancreatic Lipase Digestion of Fats Tube no. 37  C Positive (  ) or negative (  ) result Additive key:  Lipase 1L Boil lipase 4 min, then add litmus cream. 2L 3L 4L 5L 4B 5B 37  C 0C0C0C0C Color change Incubation condition Additives (5 gtt ea)  Litmus cream  Water  Pinch bile salts 15

Pancreatic Lipase Digestion of Fats Tube no. 37  C Positive (  ) or negative (  ) result Additive key:  Lipase 1L Boil lipase 4 min, then add litmus cream. 2L 3L 4L 5L 4B 5B 37  C 0C0C0C0C Color change Incubation condition Additives (5 gtt ea)  Litmus cream  Water  Pinch bile salts 15 bluish purple bluish purple pink purple bright pink pinkish purple /+ bluish purple