Enzyme Activity Experiment
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Questions and Answers

What is the formula for Vitamin A?

C20H30O

Which of the following nutrients is present in egg yolk but not in egg white?

  • Fats
  • Protein
  • Starch
  • Cholesterol (correct)

    • The specific gravity of skimmed milk is higher than that of fresh milk.

    True

    What is the main protein found in milk that can be precipitated by acid?

    <p>Casein</p> Signup and view all the answers

    What is the enzyme involved in the breakdown of hydrogen peroxide into water and oxygen?

    <p>Catalase from Liver</p> Signup and view all the answers

    Which of the following food samples tested positive for the presence of starch?

    <p>Ripe Banana</p> Signup and view all the answers

    To test for the presence of oil or fat in food samples, one should shake a small portion of the food with 3 mL of ___ in a test tube for several minutes.

    <p>ether</p> Signup and view all the answers

    Retinoic Acid serves as an extracellular messenger.

    <p>False</p> Signup and view all the answers

    Match the food sample with the positive test result obtained: (Food Samples : Test Results)

    <p>Egg Yolk (Cooked) = Proteins Cheese = Proteins, Mineral Matter Ripe Banana = Starch Peanut Butter = Fats, Glucose Carrots = Vitamin A</p> Signup and view all the answers

    What enzyme is responsible for the darkening of exposed sliced fruits when exposed to air/oxygen?

    <p>Polyphenol Oxidase (PPO) Enzyme, Tyrosinase Enzyme, Monophenol Oxidase Enzyme, Catechol Oxidizing Enzyme</p> Signup and view all the answers

    What enzyme catalyzes the decomposition of hydrogen peroxide to water and oxygen gas?

    <p>Catalase</p> Signup and view all the answers

    Oxidases are enzymes that catalyze redox reactions and use ______ as electron acceptors.

    <p>oxygen</p> Signup and view all the answers

    What happens to the catalytic effectiveness of enzymes when the potato extract is boiled?

    <p>Decreases</p> Signup and view all the answers

    What is the cause of coagulation in the coagulation test?

    <p>Presence of whey protein mainly composed of beta-lactoglobulin</p> Signup and view all the answers

    What causes the changes observed in Moore's test?

    <p>Presence of caramel due to the reducing sugar, lactose, with its reducing end, glucose</p> Signup and view all the answers

    To what class of protein does casein belong?

    <p>Casein belongs to a heterogeneous group of four phosphoproteins and phosphoglycoproteins</p> Signup and view all the answers

    What test involves the polymerization of aldehyde groups of sugars?

    <p>Moore's Test</p> Signup and view all the answers

    What chemical is used for testing the presence of phosphorus?

    <p>Conc.HNO3 + (NH4)2MoO4</p> Signup and view all the answers

    What is the Heller's Ring Test used for?

    <p>to detect the presence of albumin in urine</p> Signup and view all the answers

    Is bilirubin normally present in the urine?

    <p>False</p> Signup and view all the answers

    What does the presence of bilirubin in the urine indicate?

    <p>Possible jaundice, liver cirrhosis, hepatitis, and other liver diseases due to obstruction of the flow of bile from the gallbladder.</p> Signup and view all the answers

    What is the Benedict's Test used for?

    <p>to detect the presence of glucose in urine</p> Signup and view all the answers

    What is the Nitroprusside Test used for?

    <p>to detect the presence of acetone or aceto-acetic acid in urine</p> Signup and view all the answers

    What is the Benzidine Test used for?

    <p>to detect the presence of blood in urine</p> Signup and view all the answers

    What is the Gmelin's Test used for?

    <p>to detect the presence of bile pigments in urine</p> Signup and view all the answers

    What is the purpose of Paper Chromatography?

    <p>to separate amino acids on the basis of the difference in solubility of amino acids between 2 immiscible solvents</p> Signup and view all the answers

    What is the formula for calculating the Rf value?

    <p>Rf = distance traveled by the amino acid / distance traveled by the solvent</p> Signup and view all the answers

    What happens to salivary digestion after a 10-20 minute period?

    <p>Salivary digestion stops due to the total inactivation of ptyalin.</p> Signup and view all the answers

    What is the relationship between pH and digestion for acids?

    <p>For acid: decreasing concentration/acidity leads to an increase in digestion.</p> Signup and view all the answers

    What inorganic constituents are found in bile?

    <p>Chloride, Sulfate, and Phosphate</p> Signup and view all the answers

    What color does the litmus paper turn when tested with bile?

    <p>Blue</p> Signup and view all the answers

    Bile salts reduce the surface tension of the liquid, allowing stable foam formation when shaken.

    <p>True</p> Signup and view all the answers

    Hay's Test of Surface Tension Test is based on the principle that bile acids or bile salts have the property of reducing the ________ of the fluid.

    <p>surface tension</p> Signup and view all the answers

    What is the difference between the pH of the resting saliva and the stimulated saliva?

    <p>Resting Saliva: Slightly Basic (pH = 6.2–7.6) Stimulated Saliva: More Basic (pH = 7.0–8.0)</p> Signup and view all the answers

    Is there any relation between the pH of the saliva and the susceptibility of dental caries?

    <p>Acidic pH: essential in enamel dissolution to produce dental caries</p> Signup and view all the answers

    What is the precipitate formed when testing for mucin in saliva?

    <p>Mucin: cloudy solution with white precipitate</p> Signup and view all the answers

    What is the function of mucin in saliva?

    <p>Heavily O-glycosylated linear glycoproteins secreted by higher organisms to protect and lubricate epithelial cell surfaces.</p> Signup and view all the answers

    Which inorganic salt is found abundant in saliva?

    <p>Chloride Salts</p> Signup and view all the answers

    What is responsible for reducing the action in the Benedict's test?

    <p>Product of Starch Digestion: Maltose and Glucose</p> Signup and view all the answers

    How long did it take for a complete transformation of starch into reducing sugar?

    <p>10-20 minutes for it to completely transform into reducing sugars</p> Signup and view all the answers

    How long does salivary digestion continue in the stomach?

    <p>Salivary digestion continues in the stomach for 10-20 minutes</p> Signup and view all the answers

    What is the danger of excessive amounts of cholesterol in the bile?

    <p>Formation of gallstones</p> Signup and view all the answers

    What is the volume of the 24-hour urine?

    <p>1000-1500 mL</p> Signup and view all the answers

    What substances are responsible for the normal color of urine?

    <p>Urochrome/Urobilin and Uroerythrin</p> Signup and view all the answers

    What happens when the urine is allowed to stand for some time, exposed to air?

    <p>Bacteria causes urea to break down into ammonia, increasing pH</p> Signup and view all the answers

    What is the specific gravity range of normal urine?

    <p>1.015-1.025</p> Signup and view all the answers

    What constituents of the urine tend to precipitate when the reaction is acidic?

    <p>Sodium Urate and Uric Acid</p> Signup and view all the answers

    What is produced in the Sulphates detection test?

    <p>Barium Sulfate (BaSO4)</p> Signup and view all the answers

    What is produced in the Chloride detection test?

    <p>Silver Chloride (AgCl)</p> Signup and view all the answers

    What is the normal amount of chlorides eliminated in 24 hours?

    <p>110-250 mL per day</p> Signup and view all the answers

    In what forms are chlorides in urine eliminated?

    <p>Sodium Chloride, Potassium Chloride, and Magnesium Chloride</p> Signup and view all the answers

    Study Notes

    Enzyme Activity

    • Enzymes are complex organic compounds secreted by living cells that initiate and hasten chemical reactions without being affected themselves.
    • Enzyme activity is influenced by:
    • Concentration of the enzymes
    • Concentration of the substrate
    • Concentration of the products of the reaction
    • Temperature
    • pH
    • Inorganic salts
    • Presence of activators and inhibitors

    Oxidases from Fruits

    • Oxidases are enzymes that catalyze redox reactions and use oxygen as electron acceptors.
    • Examples of oxidases include:
    • Monophenol Oxidase (Tyrosinase): responsible for oxidizing phenol to catechol, to o-quinone and finally forms condensation brown compounds of unknown composition.
    • Polyphenol Oxidase (Catechol Oxidase): acts on catechol to form o-quinone, then the unknown brown compounds.
    • Cytochrome Oxidase: acts in conjunction with cytochrome, oxidizing phenylenediamine, which in the presence of alpha-naphthol forms indophenol.

    Peroxidase from Potato

    • Peroxidase is an enzyme that:
    • Requires a co-factor, phenol-oxidase, to complete its action.
    • Requires H2O2 as the source of oxygen, and upon which the phenol-oxidases act.

    Catalase from Liver

    • Catalase is an enzyme that:
    • Catalyzes the decomposition of hydrogen peroxide to water and oxygen gas at a rate of 40 million molecules of hydrogen peroxide per second.
    • Helps the liver filter the body by making harmful substances less toxic, such as hydrogen peroxide to water and oxygen, and alcohol to aldehyde.

    Experiment 9: Test for Nutrients in Food

    • The purpose of this experiment is to identify and understand the nutritional value with specific presence of organic molecules in foods.

    Starch Test

    • A deep blue color indicates the presence of starch in food samples.

    Glucose Test

    • A yellow to red precipitate indicates the presence of simple sugars such as glucose or fructose in food samples.

    Carr-Price Test for Vitamin A

    • A blue solution indicates the presence of Vitamin A in food samples.

    Fat Test

    • A translucent spot on white paper indicates the presence of oil or fat in food samples.

    Cholesterol Test

    • Cholesterol can be detected using microscopical examination, Acetic Anhydride–H2SO4 Test or Lieberman-Burchard Test, and Sulphuric Acid Test or Salkowski’s Test.

    Protein Test

    • A violet solution indicates the presence of proteins in food samples using the Biuret Test or Piotrowski’s Test.### Vitamin A
    • Vitamin A (Retinol) is the immediate precursor to two important active metabolites: Retinol and Retinoic Acid
    • Retinol plays a critical role in vision, while Retinoic Acid serves as an intracellular messenger that affects the transcription of a number of genes
    • Vitamins A does not occur in plants, but many plants contain carotinoid (such as beta carotene) that can be converted to vitamin A within the intestine and other tissues
    • Formula of Vitamin A: C20H30O
    • Chemical structure: 3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1-yl) nona-2,4,6,8-tetraen-1-ol

    Importance of Vitamin A

    • Vitamin A is essential for vision, growth, and maintenance of epithelial cells and mucous membranes
    • Vitamin A deficiency can lead to night blindness, xerophthalmia, and impaired immune function

    Experiment 11: Milk

    Purpose

    • To understand the reactions of milk, prepare casein, and the presence of organic materials in milk

    Apparatus and Materials

    • Test Tube, Test Tube Rack, Beaker, Funnel, Filter Paper, Bunsen Burner, Clay Flame Shield, Wire Gauze, Evaporating Dish, Vials, Litmus Papers (Blue & Red), Densimeter
    • Fresh Milk, Diluted Canned Milk, Skimmed Milk, Congo Red, Phenolphthalein Solution, Acetic Acid, 6 M & Dilute Sodium Hydroxide, Ethyl Alcohol, Ether, etc.

    Results and Observations

    • Positive Result: Violet Solution with Egg White (Cooked), Egg Yolk (Cooked), Peanut Butter, Cheese, and Dilis
    • Positive Result: White Powdery Residue with Cheese and Dilis
    • Positive Result: Bluish-Red to Cherry Red and Purple with Chloroform (CHCl3) Layer and Marked Green Fluorescence with Sulfuric Acid (H2SO4) Layer

    Importance of Milk

    • Milk is a complete food that contains proteins, fats, carbohydrates, inorganic salts, and vitamins
    • Fresh Unboiled Milk contains enzymes such as Protease, Lipase, Phosphatase, Catalase, and Peroxidase
    • Casein is the chief protein of milk and can be precipitated by acid, carrying with it the milk fat
    • Milk fat is believed to have its origin in the phospholipids of the blood
    • Milk lactose is derived from the glucose of the blood
    • Inorganic salts in milk include Calcium, Magnesium, Sodium, Phosphates, Citrates, and Chlorides

    Determination of Specific Gravity

    • Fresh Milk has a specific gravity of around 1.03
    • Skimmed Milk has a specific gravity of around 1.04
    • Milk fat is inversely proportional to specific gravity

    Coagulation Test

    • Coagulation of milk occurs due to the presence of whey protein, mainly composed of beta-lactoglobulin
    • Coagulation can be induced by acidification with acetic acid and heat

    Solubility of Casein

    • Casein is insoluble in water and dilute HCl
    • Casein is slightly soluble in 10% NaCl solution
    • Casein is soluble in dilute NaOH solution

    Moore's Test (Action of Hot Alkali)

    • Moore's Test is used to detect the presence of reducing sugars like lactose
    • The test involves mixing milk with 6 M NaOH and heating, resulting in the formation of caramel due to the reducing end of glucose

    Millon's Test

    • Millon's Test is used to detect the presence of tyrosine in casein
    • The test involves adding Millon's reagent (1 Hg : 2 HNO3) to casein, resulting in a flocculent red precipitate formation

    Preparation of Casein

    • Casein can be prepared by acidifying milk with dilute acetic acid, followed by filtering and washing with ethyl alcohol and ether
    • Casein is a heterogeneous group of four phosphoproteins and phosphoglycoproteins

    Test for Presence of Phosphorus, Calcium, and Reducing Sugar

    • The presence of phosphorus can be detected using conc. HNO3 and (NH4)2MoO4
    • The presence of calcium can be detected using (NH4)2C2O4
    • The presence of reducing sugar (lactose) can be detected using Benedict's Reagent### Whey
    • Whey contains all other substances found in milk, apart from the separated casein, such as lactalbumin, lactoglobin proteins, phosphorus, calcium, and lactose.
    • Tests for whey components:
      • Phosphorus: yellow ppt. of ammonium phosphomolybdate
      • Calcium: white ppt. of calcium oxalate
      • Lactose: orange ppt. of cuprous oxide (Benedict's)
    • Coagulation by heating: forms a coagulum consisting of lactalbumin and lactoglobin
    • Biuret test: violet solution (+)

    Milk Fat

    • Milk fat is the residue left after evaporating the ether from the filtrate obtained in no. 6
    • Milk fat forms a translucent spot when touched with a piece of paper

    Salivary Digestion

    • Purpose: to understand the reactions of saliva and stimulate salivary digestion
    • Saliva:
      • Secreted by 3 pairs of glands and hundreds of small buccal glands
      • Contains protein (mucin), enzyme (ptyalin), and inorganic salts
      • Flow is stimulated by psychic, chemical, and mechanical factors
    • Salivary digestion:
      • Hydrolysis of starch by salivary amylase (ptyalin)
      • Takes place in the buccal cavity and to a certain extent in the fundic end of the stomach
    • pH of saliva:
      • Resting saliva: slightly basic (pH = 6.2-7.6)
      • Stimulated saliva: more basic (pH = 7.0-8.0)
    • Relation between pH of saliva and susceptibility to dental caries:
      • Acidic pH is essential in enamel dissolution to produce dental caries
    • Tests on saliva:
      • Test for chloride: turbid white ppt. (AgCl)
      • Test for phosphate: clear, colorless ppt. (NH4)3PO4 12MoO3
      • Test for sulfate: slightly turbid ppt. (BaSO4)
      • Test for calcium: clear, colorless ppt. (CaC2O4)

    Starch Digestion

    • Ptyalin is responsible for starch digestion
    • Stages of starch digestion by ptyalin:
      1. Boiled starch + ptyalin = soluble starch
      2. Soluble starch + ptyalin = erythrodextrin + maltose
      3. Erythrodextrin + maltose + ptyalin = achrodextrin + maltose
      4. Achrodextrin + maltose + ptyalin = isomaltose + maltose
    • Difference between starch acid hydrolysis and starch digestion by ptyalin:
      • Starch acid hydrolysis is a nonspecific chemical reaction requiring harsh conditions to achieve complete breakdown of starch into glucose
      • Starch digestion by ptyalin is an enzymatic, specific, and controlled process occurring under physiological conditions
    • Influence of acid and alkali on starch digestion:
      • Acid: disrupts the basicity of saliva, necessary for buffering capacity
      • Alkali: ↑ concentration/alkalinity = ↑ digestion
    • Effect of gastric juice on salivary digestion:
      • Gastric juice starts protein digestion and inhibits salivary digestion
      • Salivary digestion continues in the stomach for 10-20 minutes due to the slow penetration of acidic gastric juice into the bolus

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