Q.(a) Arrange the following in decreasing order of the pKb values: C2H5NH2, C6H5NHCH3, (C2H5)2NH and C6H5NH2

Showing the 12 most recent of 63 on this concept.

1. CBSE 2026Set 56/1/11 markMCQ
   Q.The deficiency of which of the following vitamins causes increased fragility of red blood cells and muscular weakness : (A) Vitamin A (B) Vitamin K (C) Vitamin E (D) Vitamin D

   ›Reveal solutionSolution

   Vitamin E acts as a membrane antioxidant protecting red blood cells from oxidative damage; its deficiency leads to hemolysis (RBC fragility) and muscular weakness. The answer is (C).

   Vitamin E (tocopherol) is the body's primary lipid-soluble antioxidant, and understanding its role in cell membranes explains why its deficiency produces this specific clinical picture.

   Cell membranes are rich in polyunsaturated fatty acids (PUFAs), which are highly susceptible to oxidative damage through lipid peroxidation. When free radicals attack these fatty acids, they trigger a chain reaction that destroys membrane integrity. Vitamin E sits within the lipid bilayer and interrupts this chain reaction by donating electrons to free radicals, neutralizing them before they can propagate damage.

   Red blood cells are particularly vulnerable because they:

   • Have high membrane surface area relative to volume
   • Constantly carry oxygen, generating reactive oxygen species
   • Lack a nucleus and cannot synthesize new proteins to repair damage

   Skeletal muscle cells face similar oxidative stress due to their high metabolic activity and oxygen consumption.

   Why each option does or doesn't fit

   1. Vitamin E deficiency causes the exact syndrome described. Without adequate tocopherol, RBC membranes undergo peroxidation, become fragile, and rupture easily (hemolytic anemia). Muscle cell membranes similarly deteriorate, leading to myopathy and weakness. This is seen in conditions like abetalipoproteinemia or chronic fat malabsorption.

   2. Vitamin A deficiency primarily affects vision (night blindness, xerophthalmia), epithelial integrity, and immune function—not RBC fragility or muscle strength directly. …

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2. CBSE 2026Set V11 markMCQ
   Q.Doctor advised a 50 year old woman enough exposure to sunlight and addition of fish and egg yolk to her diet. Name the vitamin deficiency for the possible disease diagnosed by the doctor,

   (a) Vitamin D

   (b) Vitamin A

   (c) Vitamin C

   (d) Vitamin $\text{B}_{12}$

   ›Reveal solutionSolution

   The advice — sunlight plus fish and egg yolk — points to vitamin D deficiency.

   Vitamin D is synthesised in the skin on exposure to sunlight (UV light) and is also obtained from dietary sources such as fish (fish-liver oils) and egg yolk. Its deficiency causes rickets in children and osteomalacia (soft, weak bones) in adults, which is a particular concern in a 50-year-old woman. …

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3. CBSE 2026Set DZ1 markMCQ
   Q.Match the vitamins given in Column (I) with the diseases caused by their deficiency in Column (II): Column (I): A) Vitamin A, B) Vitamin $B_1$, C) Vitamin C, D) Vitamin K, E) Vitamin $B_{12}$. Column (II): a) Increase in clotting time of blood, b) Nightblindness, c) Beri-beri, d) Pernicious anaemia, e) Scurvy.

   (a) A-(d), B-(c), C-(e), D-(a), E-(b)

   (b) A-(b), B-(c), C-(e), D-(a), E-(d)

   (c) A-(a), B-(b), C-(c), D-(d), E-(e)

   (d) A-(b), B-(a), C-(e), D-(d), E-(c)

   ›Reveal solutionSolution

   Matching each vitamin to its deficiency disease gives A-(b), B-(c), C-(e), D-(a), E-(d) — option (b).

   Deficiency diseases of the listed vitamins:

   • Vitamin A → Night blindness (also xerophthalmia) → (b)
   • Vitamin $B_1$ (thiamine) → Beri-beri → (c)
   • Vitamin C (ascorbic acid) → Scurvy (bleeding gums) → (e)
   • Vitamin K → poor blood clotting → increase in clotting time of blood → (a) …

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4. CBSE 2026Set A1 markMCQ
   Q.Vitamin B12 contains

   (a) Cobalt

   (b) Magnesium

   (c) Iron

   (d) Nickel

   ›Reveal solutionSolution

   Vitamin B12 (cyanocobalamin) is a cobalt-containing vitamin.

   Vitamin B12, cyanocobalamin, is the only vitamin that contains a metal ion. Its structure has a corrin ring (similar to a porphyrin) with a central cobalt atom. A deficiency causes pernicious anaemia. (By comparison, chlorophyll contains magnesium …

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5. CBSE 2026Set A1 markMCQ
   Q.Riboflavin is the chemical name of which of the following ?

   (a) Vitamin B1

   (b) Vitamin B2

   (c) Vitamin B6

   (d) Vitamin B complex

   ›Reveal solutionSolution

   Riboflavin = vitamin B2.

   Riboflavin is the chemical (systematic) name for vitamin B2, a water-soluble vitamin important in energy metabolism; its deficiency causes cheilosis and cracking/sores at the corners of the mou …

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6. CBSE 2026Set ANNUAL1 mark
   Q.Scurvy disease is caused by the deficiency of Vitamin ______ (fill in the blank).

   ›Reveal solutionSolution

   Scurvy, characterised by bleeding gums and poor wound healing, results from a deficiency of vitamin C (ascorbic acid), which is …

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7. CBSE 2026Set ANNUAL1 mark
   Q.Write the name of any one source of vitamin A.

   ›Reveal solutionSolution

   Vitamin A (retinol) is a fat-soluble vitamin obtained from animal sources directly, or from plant sources as its precursor, beta-carotene.

   Vitamin A can be obtained from foods in two forms:

   • Preformed Vitamin A (retinol), found in animal sources such as fish liver oil, egg yolk, butter, and milk.
   • Provitamin A (beta-carotene), found in plant sources such as carrots, which the body converts into active Vitamin A. …

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8. CBSE 2026Set ANNUAL1 markMCQ
   Q.Riboflavin is the chemical name of:

   (a) Vitamin B1

   (b) Vitamin B2

   (c) Vitamin B6

   (d) Vitamin B12

   ›Reveal solutionSolution

   Riboflavin is the chemical/common name for Vitamin B2, a water-soluble B-complex vitamin.

   Vitamins are classified by solubility into fat-soluble (A, D, E, K) and water-soluble (B-complex, C). Among the B-complex vitamins, each has both a chemical name and a number:

   • Vitamin B1 = Thiamine
   • Vitamin B2 = Riboflavin
   • Vitamin B6 = Pyridoxine
   • Vitamin B12 = Cyanocobalamin …

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9. CBSE 2026Set ANNUAL1 markMCQ
   Q.Mohan cannot visualise properly in night. This disease is due to the lack of which vitamin?

   (a) Vitamin A

   (b) Vitamin C

   (c) Vitamin B

   (d) Vitamin D

   ›Reveal solutionSolution

   Deficiency of Vitamin A causes night blindness (nyctalopia).

   Vitamin A (retinol) is essential for synthesising the visual pigment rhodopsin in the retina's rod cells, needed for vision in dim light. A deficiency of vitamin A impairs rhodopsin regeneration, leading to difficulty seeing in low light/at night — a condition called …

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10. CBSE 2026Set ANNUAL1 mark
    Q.Write answer in one word/sentence: Write the chemical name of Vitamin B2.

    ›Reveal solutionSolution

    Vitamin B2 is chemically named riboflavin.

    Vitamin B2 is a water-soluble vitamin of the B-complex group; its chemical name is riboflavin. Its deficiency causes chei …

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11. CBSE 2026Set ANNUAL1 mark
    Q.Name the vitamin whose deficiency causes poor coagulation of blood.

    ›Reveal solutionSolution

    Vitamin K is the fat-soluble vitamin required for normal blood coagulation, so its deficiency causes poor clotting.

    Vitamins are grouped as fat-soluble ($A, D, E, K$) and water-soluble ($B$-complex and $C$). Vitamin K plays a key role in the biosynthesis of the clotting factor prothrombin in the liver. Without adequate vitami …

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12. CBSE 2025Set X11 markMCQ
    Q.Incorrect statement regarding vitamins,

    (a) Excess vitamin intake is harmful

    (b) Most of the vitamins contain amino groups

    (c) Vitamins can be produced by plants

    (d) Vitamin deficiency causes diseases

    ›Reveal solutionSolution

    The false statement is (b) — most vitamins are NOT amines; they are a chemically diverse class and only a handful contain amino groups.

    Evaluating each statement:

    • (a) Excess vitamin intake is harmful — TRUE. Fat-soluble vitamins (A, D, E, K) are stored in the body and excess intake causes hypervitaminosis (toxicity).
    • (b) Most of the vitamins contain amino groups — FALSE. Vitamins are chemically very varied (e.g. vitamin C is an acid/lactone, vitamin A is an alcohol, vitamin D is a steroid derivative). Only a few (e.g. some B-group vitamins like $\text{B}_1$, $\text{B}_6$, $\text{B}_{12}$) contain nitrogen/amino groups — they are the exception, not the majority. The word "vitamine" was coined historically because the first one studied contained an amine, but this does not hold for most vitamin …

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