physioex 8

• hydrolases: enzymes that catalyze bond cleavages by reaction with water (break down organic food molecules)
• hydrolytic enzymes are highly specific in its action
• IKI assay detects the presence of starch or cellulose, turning blue-black
• Benedict's assay detects reducing sugars, such as glucose or maltose
• enzyme: large protein molecules produced by body cells
• catalyst: a substance that increases the rate of a chemical reaction without being used up in the reaction
• control: known standard to compare against
• salivary amylase hydrolysis starch to form maltose
• amylase is denatured when boiled or in unideal pH (pH 2 or 9)
• IKI readings

  • positive IKI: no starch digestion
  • negative IKI: starch digestion
• Benedict's readings

  • positive reading: starch digestion end products present
  • negative reading: no starch digestion end products present
• substrate is the substance the enzyme acts on
• enzyme has a pocket called active site that substrate must fit into for catalysis to occur
• although cellulose is a polymer of glucose like starch, it cannot be digested by amylase because of differing molecule linkage
• substrate specificity of peptidase is peptides
• bacteria aid in digestion of cellulose due to cellulase enzyme, breaking down to glucose or maltose
• with amylase activity, starch decreases and sugar increases
• enzyme assay: chemical method of detecting the presence of digested substances
• BPNA releases a yellow dye product when hydrolyzed

  • solutions turn yellow in presence of pepsin
• pepsin needs a highly acidic environment to activate it
• substrate specificity of pepsin is protein and peptides
• boiling inactivates pepsin as it denatures the protein
• chief cells produce pepsin
• spectrophotometer shines light through a substance and measures how much light is absorbed
• optical density: the ability of a substance to absorb or reflect light.
• colorless solutions do not absorb light and have an optical density near zero
• solution containing fatty acids liberated by lipase activity will have a LOWER pH
• triglycerides are emulsified by bile to droplets which increase the surface area allowing for lipase to better break it down to a monoglyceride and two fatty acids
• bile salts act like a detergent, separating lipid clumps and increasing surface area accessible to lipase
• pH of 7.0 is ideal for pancreatic lipase digestion
• when a pH is too low, a decrease in pH may be hard to measure for lipase activity