Choose wrong statement regarding proteins :

Correct — option (3), About 30 percent of our body weight comes from proteins.

The stem asks for the wrong statement. Option (3) overstates how much of body weight is protein.

Water is the bulk of body weight. The National Institute of Nutrition (NIN), Hyderabad, states in its Dietary Guidelines for Indians (2011): "Water accounts for 70% of our body weight." Protein shares the remaining 30 percent with fat, minerals and everything else, so it can be only a part of that 30 percent.

The US National Institute of General Medical Sciences (NIGMS) adds a second measure in its blog post 'Proteins by the Numbers' (15 January 2025): proteins make up 42 percent of body weight not counting water. Protein is a part of the non-water weight, not all of it.

So About 30 percent of our body weight comes from proteins is the wrong statement.

The other three statements agree with NIN's manual: it names animal and plant foods as rich protein sources, describes proteins as composed of amino acids, and groups protein-rich foods as body building foods.

The idea to remember: water is the largest share of body weight; protein is a part of what remains, below 30 percent.

Why the others are wrong

• (1)
  We obtain proteins from both animals and plants. — This statement is correct, so it cannot be the answer to a question asking for the wrong one.

  NIN's manual names animal foods like milk, meat, fish and eggs and plant foods such as pulses and legumes as rich sources of proteins.

  It adds a difference in quality: animal proteins provide all the essential amino acids in right proportions, while a combination of cereals, millets and pulses provides most of the amino acids.

• (2)
  Proteins are made of amino acids. — This statement is correct. NIN's manual describes proteins as complex molecules composed of different amino acids, so amino acids are the units proteins are built from.

  Some amino acids, termed essential, have to be obtained from dietary protein because the human body does not synthesize them. The non-essential ones can be synthesized in the body.

• (4)
  Proteins are called building block of our body. — This statement is treated as correct in RPSC's key. NIN's manual describes proteins as primary structural and functional components of every living cell, and its classification of foods by function lists proteins under body building foods.

  NIN also notes that almost half the protein in our body is in muscle, and the rest in bone, cartilage and skin.

Proteins are one of the three macronutrients, with carbohydrates and fats, that the body needs in large amounts. A protein consists of amino acids linked by peptide bonds.

NIN's manual separates essential amino acids, which must come from food, from non-essential ones the body can make. Animal proteins supply all essential amino acids in right proportions; cereals, millets and pulses eaten together complement each other.

NIN calls proteins primary structural and functional components of every living cell. Almost half the body's protein is in muscle, the rest in bone, cartilage and skin. Proteins also provide energy: 4 Kcal per gram, the same as carbohydrates, against 9 Kcal per gram for fats.

Key facts

• NIN's Dietary Guidelines for Indians (2011) describe proteins as complex molecules composed of different amino acids.
• Essential amino acids must come from dietary protein because the human body does not synthesize them; non-essential amino acids can be synthesized.
• NIN: almost half the protein in the body is in muscle; the rest is in bone, cartilage and skin.
• Proteins and carbohydrates provide 4 Kcal per gram; fats provide 9 Kcal per gram (NIN, 2011).
• NIN states water accounts for 70% of body weight; NIGMS (post of January 2025) puts proteins at 42 percent of body weight not counting water.

Common traps

• "Building block" works at two levels. NIN's glossary calls the amino acid the fundamental building block of proteins, while its food table lists proteins under body building foods. Option (4) uses the body level.
• A share of diet calories is not a share of body weight. NIN's 10-15% is the part of total calories that should come from proteins; the 70% figure is water's part of body weight.
• Plant proteins differ in quality, not in being protein. NIN says plant proteins are low in some essential amino acids, which a mix of cereals, millets and pulses makes up.

• practice — not a real PYQ

  According to the National Institute of Nutrition's Dietary Guidelines for Indians (2011), which of the following statements is NOT correct?

  • (a)Proteins provide energy of 4 Kcal per gram.
  • (b)Almost half the protein in our body is in the form of muscle.
  • (c)Essential amino acids are synthesized in the human body.
  • (d)Pulses and legumes are rich sources of proteins.
  Answer(3) — NIN says essential amino acids have to be obtained from proteins in the diet because they are not synthesized in the human body. Options (1), (2) and (4) are each stated in the same manual, so they are correct statements.
• practice — not a real PYQ

  In a balanced diet, about what share of total calories should come from proteins, according to NIN's Dietary Guidelines for Indians (2011)?

  • (a)50-60 percent
  • (b)10-15 percent
  • (c)20-30 percent
  • (d)70 percent
  Answer(2) — NIN recommends about 10-15% of total calories from proteins. Option (1) is its range for carbohydrates, option (3) is its range for visible and invisible fat, and option (4) is the manual's figure for water's share of body weight, not a calorie share.