Nutrition & Biomolecules – NDA Biology PYQs

NDA 2025-I

Q. 1. A chain of peptide containing linear sequences of amino acid linked by peptide bonds best represent the

(a) Primary structure

(b) Secondary structure

(c) Tertiary structure

(d) Quaternary structure

Answer: (a) Primary structure

Explanation: Protein structure has four levels. The primary structure is the simplest level. It is the linear sequence of amino acids linked by peptide bonds. Secondary structure involves folding into helices or sheets. Tertiary structure is the three-dimensional shape of a single polypeptide. Quaternary structure involves multiple polypeptide subunits. Concept Tested: Primary structure of proteins: linear amino acid sequence linked by peptide bonds

Q. 2. What happens when the fat and oil containing food materials are left outside for a long time?

(a) Fats and oils in the food get oxidized

(b) Fats and oils in the food get reduced

(c) Fats and oils in the food get ice-covered

(d) No reaction takes place

Answer: (a) Fats and oils in the food get oxidized

Explanation: When fats and oils are exposed to air over a long period, they undergo oxidation. This process is called rancidity. Oxygen in the air reacts with the unsaturated fatty acid chains. The products formed have an unpleasant smell and taste. Antioxidants such as vitamin E are added to foods to slow rancidity. Concept Tested: Rancidity: oxidation of fats and oils on prolonged exposure to air

★ JOVIK Exam Insight NDA has tested the chemistry of food spoilage. Rancidity is oxidation: not reduction, not freezing. The key word in the question is “long time outside,” which points directly to oxidation by atmospheric oxygen.

NDA 2024-II

Q. 3. Which one among the following combinations most appropriately represent the components of balanced diet?

(a) Carbohydrate, vitamins, proteins, fat, minerals, fibres and water

(b) Carbohydrate, vitamins, proteins, fat and minerals

(c) Carbohydrate, vitamins, proteins, minerals and water

(d) Vitamins, proteins, fat, minerals, fibres and water

Answer: (a) Carbohydrate, vitamins, proteins, fat, minerals, fibres and water

Explanation: A balanced diet must include all seven major components: carbohydrates, proteins, fats, vitamins, minerals, dietary fibre, and water. Option (a) is the only choice that includes all seven. Options (b), (c), and (d) each omit one or more essential components. Concept Tested: Seven components of a balanced diet

NDA 2023-I

Q. 4. Browning of the chopped apple can be minimized by:

(a) using table sugar.

(b) preserving in a container.

(c) using lemon juice.

(d) using milk of magnesia.

Answer: (c) using lemon juice.

Explanation: Browning of cut apple is caused by enzymatic oxidation. The enzyme polyphenol oxidase reacts with phenolic compounds and oxygen to produce brown pigments. Lemon juice contains ascorbic acid (vitamin C), which is an antioxidant. It reduces the oxidised compounds and inhibits the enzyme, preventing browning. Table sugar and milk of magnesia do not inhibit this reaction effectively. Concept Tested: Enzymatic browning prevention: ascorbic acid in lemon juice acts as antioxidant

★ JOVIK Exam Insight Enzymatic browning of cut fruits (apple, banana, potato) is a recurring NDA Biology topic. The cause is polyphenol oxidase acting on phenolic compounds in air. Lemon juice (ascorbic acid) prevents it by acting as an antioxidant and enzyme inhibitor.

NDA 2017-II

Q. 5. Intake of which one of the following food components should be minimized by patients having Gouty Arthritis due to elevated serum uric acid level?

(a) Food fibres

(b) Nucleic acids

(c) Lipids

(d) Carbohydrates

Answer: (b) Nucleic acids

Explanation: Uric acid is the end product of purine metabolism in humans. Purines are nitrogen-containing bases found in nucleic acids (DNA and RNA). When nucleic acids are metabolised, purines are broken down to uric acid. Patients with gout have high uric acid levels. They should reduce intake of purine-rich foods, meaning foods high in nucleic acids, such as organ meats, red meat, and certain seafood. Concept Tested: Uric acid as the metabolic product of purine (nucleic acid) breakdown; relevance to gout

NDA 2017-I

Q. 6. Which one of the following statements is NOT correct?

(a) All proteins are enzymes

(b) Mostly enzymes are proteins

(c) All fats are energy rich compounds

(d) Glucose is a common carbohydrate

Answer: (a) All proteins are enzymes

Explanation: Not all proteins are enzymes. Proteins have many roles: structural (collagen, keratin), transport (haemoglobin), hormonal (insulin), and enzymatic. Only a subset of proteins function as enzymes. However, most enzymes are proteins: this makes option (b) correct. Fats are energy-rich and glucose is indeed a common carbohydrate. Concept Tested: Distinction between proteins and enzymes: not all proteins are enzymes

Q. 7. Sugarcane is one of the important cash crops in India. It is grown to obtain

(a) Starch

(b) Glucose

(c) Fructose

(d) Sucrose

Answer: (d) Sucrose

Explanation: Sucrose is the main sugar extracted from sugarcane. It is a disaccharide composed of one glucose unit and one fructose unit. Sugarcane juice is rich in sucrose. When processed, it yields the sugar used in homes and industries. Starch is a polysaccharide found in grains and tubers, not in sugarcane juice. Concept Tested: Sucrose as the principal sugar of sugarcane

NDA 2015-I

Q. 8. All life forms contain “molecules of life”. These are

(a) Carbohydrates

(b) Proteins

(c) Nucleic acids

(d) All of the above

Answer: (d) All of the above

Explanation: The four major classes of biological macromolecules: carbohydrates, proteins, lipids, and nucleic acids: are collectively called the “molecules of life.” All living organisms, from bacteria to humans, contain all of these. Among the options, carbohydrates, proteins, and nucleic acids are all present in every life form. The correct answer is “All of the above.” Concept Tested: Biological macromolecules as the molecules of life: carbohydrates, proteins, and nucleic acids present in all organisms

NDA 2014-II

Q. 9. Consider the following statements:

1. Carbohydrates are the only source of energy to humans.

2. Fats give maximum energy on oxidation as compared to other foods.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (b) 2 only

Explanation: Statement 1 is incorrect. Humans obtain energy from carbohydrates, fats, and proteins. Carbohydrates are the preferred energy source, not the only source. Statement 2 is correct. Fats yield approximately 9 kcal per gram on oxidation, compared to 4 kcal per gram for carbohydrates and proteins. Fats therefore provide the maximum energy per gram. Concept Tested: Energy yield of macronutrients: fats yield the most energy per gram (9 kcal/g) vs carbohydrates and proteins (4 kcal/g)

★ JOVIK Exam Insight NDA frequently tests the energy content of macronutrients. The key fact: fats = 9 kcal/g, carbohydrates = 4 kcal/g, proteins = 4 kcal/g. Carbohydrates are the preferred but NOT the only energy source.

NDA 2014-I

Q. 10. In honey, which one among the following sugars predominates?

(a) Sucrose

(b) Fructose

(c) Galactose

(d) Maltose

Answer: (b) Fructose

Explanation: Honey is primarily composed of fructose and glucose. Fructose is the predominant sugar in most types of honey, typically making up about 38–40% of its sugar content. Glucose constitutes around 30–35%. Sucrose is present in very small amounts. Galactose and maltose are not significant components of honey. Concept Tested: Fructose as the predominant sugar in honey

Q. 11. Dropsy is a disease caused due to adulteration in

(a) Ghee

(b) Arhar Dal

(c) mustard oil

(d) turmeric powder

Answer: (c) mustard oil

Explanation: Epidemic dropsy is caused by adulteration of mustard oil with argemone oil (extracted from Argemone mexicana seeds). Argemone oil contains toxic alkaloids, especially sanguinarine and dihydrosanguinarine. These toxins damage blood capillaries, causing fluid accumulation (dropsy: oedema). This adulteration has caused mass poisoning episodes in India. Concept Tested: Epidemic dropsy: caused by mustard oil adulterated with argemone oil

NDA 2013-II

Q. 12. Solutions of three enzymes were prepared namely lipase, trypsin and amylase, in order to remove stains from a piece of cloth. Out of these three enzyme solutions, only lipase could completely remove the stain. This indicates that the stain was due to

(a) Oil

(b) Protein

(c) Mixture of protein and oil

(d) Starch containing plant pigment

Answer: (a) Oil

Explanation: Lipase breaks down fats and oils (lipids). Trypsin is a protease that breaks down proteins. Amylase breaks down starch (a carbohydrate). Since only lipase removed the stain, the stain must be made of a substance that lipase acts on: that is, oil or fat. A protein stain would have been removed by trypsin. A starch stain would have been removed by amylase. Concept Tested: Enzyme specificity: lipase acts on lipids, trypsin on proteins, amylase on starch

NDA 2013-I

Q. 13. Which one among the following statements about a healthy diet is correct?

(a) Regular eating of high-energy snacks between meals is healthy since it provides energy and vitamins in plenty

(b) Fruits and vegetables make a good choice because their energy content is high

(c) A balanced diet must contain plenty of fat and protein with little carbohydrates and fibre

(d) An optimal quantity of fat, protein, carbohydrate with adequate amount of water and fibre makes a healthy diet

Answer: (d) An optimal quantity of fat, protein, carbohydrate with adequate amount of water and fibre makes a healthy diet

Explanation: A healthy diet must contain all macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals) in appropriate quantities, along with adequate water and dietary fibre. Option (a) is incorrect: high-energy snacks are not healthy choices. Option (b) is incorrect: fruits and vegetables are valued for vitamins, minerals, and fibre, not high energy content. Option (c) is incorrect: fibre and carbohydrates are essential, not to be minimised. Concept Tested: Characteristics of a healthy, balanced diet

NDA 2012-I

Q. 14. Statement I: After cutting an apple or a banana, the colour of the cut surface becomes brown.

Statement II: Polyphenolic compounds present in fruits get oxidized in air and show colour.

(a) Both the statements are individually true and Statement II is the correct explanation of Statement I

(b) Both the statements are individually true but Statement II is not the correct explanation of Statement I

(c) Statement I is true but Statement II is false

(d) Statement I is false but Statement II is true

Answer: (a) Both the statements are individually true and Statement II is the correct explanation of Statement I

Explanation: Statement I is correct: cut surfaces of apples and bananas turn brown. Statement II is also correct: this browning occurs because polyphenolic compounds (such as chlorogenic acid) in the fruit are oxidised by the enzyme polyphenol oxidase when exposed to air. The oxidised products are brown-coloured quinones. Statement II directly and correctly explains Statement I. Concept Tested: Enzymatic browning: oxidation of polyphenolic compounds by polyphenol oxidase in air

Q. 15. Balanced diet should have approximately

(a) 1/5 protein, 3/5 fat and 1/5 carbohydrate

(b) 3/5 protein, 1/5 fat and 1/5 carbohydrate

(c) 1/5 protein, 1/5 fat and 3/5 carbohydrate

(d) 1/2 protein, 1/4 fat and 1/4 carbohydrate

Answer: (c) 1/5 protein, 1/5 fat and 3/5 carbohydrate

Explanation: A standard balanced diet derives the majority of its calories from carbohydrates. Dietary guidelines recommend approximately 60% carbohydrates, 20% proteins, and 20% fats: corresponding to option (c): 1/5 protein, 1/5 fat, and 3/5 carbohydrate. Carbohydrates are the primary and preferred energy source for the body. Concept Tested: Approximate macronutrient proportions in a balanced diet: carbohydrates ~60%, protein ~20%, fat ~20%

Q. 16. Carbohydrates are stored in plants and animals in the form of

(a) cellulose and glucose respectively

(b) starch and glycogen respectively

(c) starch and glucose respectively

(d) cellulose and glycogen respectively

Answer: (b) starch and glycogen respectively

Explanation: In plants, carbohydrates are stored as starch, which is a polysaccharide made of glucose units. In animals, carbohydrates are stored as glycogen, also a glucose polymer, but more highly branched. Cellulose is a structural polysaccharide in plant cell walls, not a storage carbohydrate. Glucose is the transport form, not the stored form. Concept Tested: Carbohydrate storage: starch in plants, glycogen in animals

★ JOVIK Exam Insight This is a high-frequency NDA concept. Plants store carbohydrates as starch; animals store them as glycogen. Cellulose is structural: do not confuse it with the storage form.

NDA 2010-II

Q. 17. Consider the following items

1. Proteins, Carbohydrates, and Fats

2. Vitamins

3. Minerals

4. Water

Which of the above are considered as the constituents of food?

(a) 1, 2 and 4 only

(b) 1 and 3 only

(c) 2 and 3 only

(d) 1, 2, 3 and 4

Answer: (d) 1, 2, 3 and 4

Explanation: All four: macronutrients (proteins, carbohydrates, fats), vitamins, minerals, and water: are recognised constituents of food. Each group plays an essential role. Macronutrients provide energy and building materials. Vitamins and minerals regulate body processes. Water is the medium for all biological reactions. Concept Tested: All major components of food: macronutrients, vitamins, minerals, and water

NDA 2010-I

Q. 18. Biological catalysts in living organisms are known as

(a) hormones

(b) vitamins

(c) steroids

(d) enzymes

Answer: (d) enzymes

Explanation: Enzymes are biological catalysts. They speed up chemical reactions in living organisms without being consumed in the process. Most enzymes are proteins. Hormones are chemical messengers. Vitamins are organic compounds needed in small amounts for various functions. Steroids are lipid-based compounds with a different structure and function. Concept Tested: Enzymes as biological catalysts in living organisms

NDA 2009-I

Q. 19. Which one of the following is not an enzyme?

(a) Amylase

(b) Pepsin

(c) Somatotrophin

(d) Trypsin

Answer: (c) Somatotrophin

Explanation: Amylase breaks down starch; pepsin digests proteins in the stomach; trypsin is a protease produced by the pancreas. All three are enzymes. Somatotrophin is a hormone, not an enzyme. It is also called growth hormone (GH) and is secreted by the anterior pituitary gland. It promotes growth of bones and tissues. Concept Tested: Somatotrophin (growth hormone) is a hormone, not an enzyme

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