Tag: evs

Questions Related to evs

The digestive juices break down into simpler substance

  1. Proteins

  2. Hydrochloric acid

  3. Fatty acid

  4. None of the above


Correct Option: A
Explanation:

Gastric acid is a digestive fluid, formed in the stomach. It is composed of hydrochloric acid (HCl) 0.05–0.1 M (roughly 5,000–10,000 parts per million) potassium chloride (KCl) and sodium chloride (NaCl). The acid plays a key role in digestion of proteins, by activating digestive enzymes, and making ingested proteins unravel so that digestive enzymes break down the long chains of amino acids. The highly acidic environment in the stomach lumen causes proteins from food to lose their characteristic folded structure (or denature). This exposes the protein's peptide bonds. The gastric chief cells of the stomach secrete enzymes for protein breakdown (inactive pepsinogen, and in infancy rennin). Hydrochloric acid activates pepsinogen into the enzyme pepsin, which then helps digestion by breaking the bonds linking amino acids, a process known as proteolysis. In addition, many microorganisms have their growth inhibited by such an acidic environment, which is helpful to prevent infection. HCl is digestive juice. Fatty acids are digested by bile acids.

Therefore, the correct answer is option A.

Which carbohydrate gives red colour when iodine solution is added to it?

  1. Starch

  2. Glycogen

  3. Dextrin

  4. Insulin


Correct Option: B
Explanation:

Iodine test is used to distinguish between the presence of starch and glycogen and other saccharides.
When starch solution is treated with iodine, it gives a blue color. The blue color develops because of the trapping of iodine in the helical coils of amylose. When this test solution is heated, the color disappears due to disruption of the helical coils of amylose and the color reappears upon cooling, due to the reformation of helical coils. Glycogen however gives red color with iodine.
Therefore, the correct answer is option B.

Which of the following foods turns blue-black with iodine solution?

  1. Milk

  2. Groundnut

  3. Tomato

  4. Raw potato


Correct Option: D
Explanation:

  • Raw potato contains approximately 17% starch. when iodine solution added to the raw potato sample, it turns blue-black. Iodine reacts with the starch present in the raw potato which results in the formation of blue-black colored complex. 

Hence option D is the correct answer.

Egg white, turns violet when two drops of copper sulphate and ten drops of caustic soda is added to it. This indicates the presence of 

  1. Starch.

  2. Proteins.

  3. Fats.

  4. Vitamins.


Correct Option: B
Explanation:

When two drops of copper sulphate and ten drops of caustic soda or NaOH is added to egg, it turns violet. This indicates the presence of proteins.
This is Biuret's test and the principle is simple as follows:
In the presence of alkaline medium (caustic soda or NaOH), the Cu2+ ions get reduced to Cu+ and binds to the egg proteins, thereby giving a violet color.
Therefore, the correct answer is option B.

Which of the following agent is used to detect the presence of fat in the food product?

  1. Methyl alcohol

  2. Ethyl alcohol

  3. Sodium hydroxide

  4. Iodine solution


Correct Option: B
Explanation:

Shake or crush the food to make it dissolve. Filter or dilute the food and ethanol mix so that you get a clear liquid (a solution of fat in ethanol). Add this to a test tube of water. A white (milk-like) emulsion indicates the presence of fats or oils.

So, the correct option is 'Ethyl alcohol'.

Starch is tested with ................  solution.

  1. Caustic soda

  2. Salt

  3. HCl

  4. Iodine


Correct Option: D
Explanation:

The iodine test is used to test for the presence of starch. Iodine dissolved in an aqueous solution of potassium iodide reacts with the starch, producing a purple-black colour. The intensity of the colour decreases with increasing temperature and with the presence of water-soluble organic solvents, such as ethanol.

What compounds form fats and oils?

  1. Carboxylic acids +Alcohol

  2. Carbon Compounds +water

  3. Carbon Dioxide + Alcohol

  4. Carbon Monoxide +Alcohol


Correct Option: A

Which of the following is used to test presence of starch?

  1. Cheek peel

  2. Onion

  3. Potato

  4. None of the above


Correct Option: C
Explanation:

A chemical test for starch is to add iodine solution (red) and see if it turns blue/black in colour. It is possible to distinguish starch from other carbohydrates using this iodine solution test. For example, if iodine is added to an peeled potato then it will turn black. 

Which of the following test are used for detection of protein?

  1. Biuret test

  2. Iodine test

  3. Protein test

  4. Glucose test


Correct Option: A
Explanation:

The Biuret test is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper (II) ion forms violet-coloured coordination complexes in an alkaline solution. The Biuret reaction can be used to assess the concentration of proteins because peptide bonds occur with the same frequency per amino acid in the peptide.