Which one among the following cells produces antibodies against a foreign antigen ?
- A.Lymphocytes
- B.Erythrocytes
- C.Eosinophils
- D.Platelets
Correct answer
Explanation
The correct answer is A, Lymphocytes. Antibodies are made by B-lymphocytes, a kind of white blood cell, after they meet a foreign antigen.
When a germ or other foreign substance enters the body, B-lymphocytes that recognise its antigen multiply and turn into plasma cells. Each plasma cell releases large amounts of antibodies, Y-shaped proteins called immunoglobulins, which bind to that antigen and mark it for destruction. Some B-cells become memory cells, so a second infection is fought faster; this is the basis of vaccination. T-lymphocytes help the B-cells and kill infected cells directly.
B is wrong because erythrocytes are red blood cells that carry oxygen with haemoglobin and have no nucleus in mammals. C is wrong because eosinophils are white cells that fight parasites and take part in allergies, but do not make antibodies. D is wrong because platelets help blood to clot.
Exam tip: B-cells make antibodies, T-cells kill infected cells, RBCs carry oxygen, platelets clot blood.
Practice Questions
View allWhich of the following statements about electromagnetic waves, sound waves and water waves is/are correct ? 1. They exhibit reflection 2. They carry energy 3. They exert pressure 4. They can travel in vacuum Select the correct answer using the code given below :
- A.1,2 and 3
- B.2 and 4
- C.1 and 3 only
- D.1 only
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All three kinds of wave reflect, carry energy and exert pressure, but only electromagnetic waves can travel through a vacuum.
Read the full explanation →Which one of the following is NOT the unit of energy?
- A.Joule
- B.Watt-hr
- C.Newton-metre
- D.kg-metre/sec²
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A kilogram-metre per second squared is mass times acceleration, which is force; it is the newton, not a unit of energy.
Read the full explanation →To protect steel and iron from rusting, a thin layer of which one of the following metals is applied?
- A.Magnesium
- B.Zinc
- C.Aluminium
- D.Lead
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Coating iron or steel with a thin layer of zinc is called galvanisation, and it is the most common way to protect them from rusting.
Read the full explanation →In an electric circuit, a wire of resistance 10 Ω is used. If this wire is stretched to a length double of its original value, the current in the circuit would become :
- A.half of its original value.
- B.double of its original value.
- C.one-fourth of its original value.
- D.four times of its original value.
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Stretching the wire to twice its length makes its resistance four times larger, so at the same voltage the current falls to a quarter.
Read the full explanation →Which one of the following scientists mentioned that an electron in an atom could revolve in certain stable orbits without the emission of radiant energy ?
- A.Ernest Rutherford
- B.J.J. Thomson
- C.Niels Bohr
- D.Albert Einstein
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In his 1913 model of the atom, Bohr proposed that electrons move in certain fixed orbits, called stationary states, in which they do not radiate energy.
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