Enzyme Activity Experiment

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?

Casein Signup and view all the answers

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

Catalase from Liver Signup and view all the answers

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

Ripe Banana 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.

ether Signup and view all the answers

Retinoic Acid serves as an extracellular messenger.

False Signup and view all the answers

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

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

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

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

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

Catalase Signup and view all the answers

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

oxygen Signup and view all the answers

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

Decreases Signup and view all the answers

What is the cause of coagulation in the coagulation test?

Presence of whey protein mainly composed of beta-lactoglobulin Signup and view all the answers

What causes the changes observed in Moore's test?

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

To what class of protein does casein belong?

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

What test involves the polymerization of aldehyde groups of sugars?

Moore's Test Signup and view all the answers

What chemical is used for testing the presence of phosphorus?

Conc.HNO3 + (NH4)2MoO4 Signup and view all the answers

What is the Heller's Ring Test used for?

to detect the presence of albumin in urine Signup and view all the answers

Is bilirubin normally present in the urine?

False Signup and view all the answers

What does the presence of bilirubin in the urine indicate?

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

What is the Benedict's Test used for?

to detect the presence of glucose in urine Signup and view all the answers

What is the Nitroprusside Test used for?

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

What is the Benzidine Test used for?

to detect the presence of blood in urine Signup and view all the answers

What is the Gmelin's Test used for?

to detect the presence of bile pigments in urine Signup and view all the answers

What is the purpose of Paper Chromatography?

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

What is the formula for calculating the Rf value?

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

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

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

What is the relationship between pH and digestion for acids?

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

What inorganic constituents are found in bile?

Chloride, Sulfate, and Phosphate Signup and view all the answers

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

Blue Signup and view all the answers

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

True 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.

surface tension Signup and view all the answers

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

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

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

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

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

Mucin: cloudy solution with white precipitate Signup and view all the answers

What is the function of mucin in saliva?

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

Which inorganic salt is found abundant in saliva?

Chloride Salts Signup and view all the answers

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

Product of Starch Digestion: Maltose and Glucose Signup and view all the answers

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

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

How long does salivary digestion continue in the stomach?

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

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

Formation of gallstones Signup and view all the answers

What is the volume of the 24-hour urine?

1000-1500 mL Signup and view all the answers

What substances are responsible for the normal color of urine?

Urochrome/Urobilin and Uroerythrin Signup and view all the answers

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

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

What is the specific gravity range of normal urine?

1.015-1.025 Signup and view all the answers

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

Sodium Urate and Uric Acid Signup and view all the answers

What is produced in the Sulphates detection test?

Barium Sulfate (BaSO4) Signup and view all the answers

What is produced in the Chloride detection test?

Silver Chloride (AgCl) Signup and view all the answers

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

110-250 mL per day Signup and view all the answers

In what forms are chlorides in urine eliminated?

Sodium Chloride, Potassium Chloride, and Magnesium Chloride 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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Description

Observe how enzymes react with sliced fruits, leading to darkening. Analyze the reactions and understand enzyme activity.