Cell – What is a Cell? The Unit of Life: NEET MCQs with Answers

15 free questions on Cell – What is a Cell? The Unit of Life for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: What is a Cell? The Unit of Life

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Question 1

Previous-year question
The magnification of a compound microscope is not connected with the [AIPMT 1990]
  1. Numerical aperture
  2. Focal length of the objective
  3. Focal length of the eyepiece
  4. Tube length
Show answer
Answer: (A) Numerical aperture
Explanation: Magnification is the power of enlargement and depends upon the focal lengths of the objective and the eyepiece and on the length of the body tube. The numerical aperture of the objective lens is a measure of its light-gathering ability and governs resolving power, not magnification.

Question 2

Previous-year question
Resolving power is the ability to [AIPMT 1991]
  1. Distinguish two trees
  2. Distinguish two closely placed objects
  3. Distinguish amongst organelles
  4. Magnify the image
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Answer: (B) Distinguish two closely placed objects
Explanation: Resolving power is the capacity of a microscope to distinguish between two points that are situated very close together, that is, the smallest distance by which two objects lying close to one another can be separated and still be seen as distinct. Higher resolution makes the image clearer; magnification is a separate property.

Question 3

Previous-year question
The electron microscope has a high resolving power. This is due to [AIPMT 1992]
  1. Electromagnetic lenses
  2. Very low wavelength of the electron beam
  3. Low wavelength of the light source used
  4. High numerical aperture of the glass lenses used
Show answer
Answer: (B) Very low wavelength of the electron beam
Explanation: In an electron microscope the illuminating beam consists of electrons, whose wavelength is thousands of times shorter than that of visible light. Because resolution improves as wavelength decreases, this very low wavelength is what gives the instrument its high resolving power.

Question 4

Previous-year question
A student wishes to study cell structure under a light microscope having a 10X eyepiece and a 45X objective. Which one of the following colours of light should be used to illuminate the object so as to obtain the best possible resolution? [AIPMT 2005]
  1. Blue
  2. Green
  3. Yellow
  4. Red
Show answer
Answer: (A) Blue
Explanation: The resolving power of a microscope is inversely proportional to the wavelength of the light used, so the shorter the wavelength the better the resolution. Among the four colours listed, blue light has the shortest wavelength and will therefore give the maximum resolution.

Question 5

Previous-year question
A major breakthrough in the study of cells came with the development of the electron microscope. This is because [AIPMT 2006]
  1. The resolving power of the electron microscope is 200–350 nm as compared with 0.1–0.2 nm for the light microscope
  2. An electron beam can pass through thick materials, whereas light microscopy requires thin sections
  3. The electron microscope is more powerful than the light microscope as it uses a beam of electrons whose wavelength is much longer than that of photons
  4. The resolving power of the electron microscope is much higher than that of the light microscope
Show answer
Answer: (D) The resolving power of the electron microscope is much higher than that of the light microscope
Explanation: The resolving power of the electron microscope is far greater than that of the light microscope because electrons have a much shorter wavelength than photons of visible light. Since resolution is inversely proportional to wavelength, the electron microscope can distinguish much finer structural detail, which made the study of cell ultrastructure possible.

Question 6

Previous-year question
Hammerling's experiments on Acetabularia demonstrated the role of the [1992]
  1. chromosomes in heredity
  2. cytoplasm in controlling differentiation
  3. nucleocytoplasmic ratio
  4. nucleus in heredity
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Answer: (D) nucleus in heredity
Explanation: Because the regenerated cap always finally took the form of the species contributing the nucleus, Hammerling established that the hereditary information determining cell form resides in the nucleus. The cytoplasm can direct the first regeneration only because it still contains messenger molecules previously supplied by the nucleus.

Question 7

Previous-year question
Hammerling's experiments on Acetabularia involved the exchange of [1991]
  1. the rhizoid and the stalk
  2. cytoplasm
  3. gametes
  4. the nucleus
Show answer
Answer: (A) the rhizoid and the stalk
Explanation: Hammerling grafted the stalk of one species on to the rhizoid of another. The cap that regenerated at first showed intermediate characters, but after removal it regrew in the form characteristic of the species that had supplied the rhizoid — and therefore the nucleus.
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Question 8

Previous-year question
Auxetic growth is an increase in [1994]
  1. fatty tissue
  2. cell volume only
  3. intercellular material
  4. cell number only
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Answer: (B) cell volume only
Explanation: Auxetic growth is growth achieved purely by enlargement of the existing cells, without any increase in their number. It is seen in nematodes and rotifers, which have a fixed number of cells from hatching, and is contrasted with multiplicative growth, in which cell division adds new cells.

Question 9

Previous-year question
The main arena of the various activities of a cell is the [2009]
  1. cytoplasm
  2. plasma membrane
  3. nucleus
  4. mitochondrion
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Answer: (A) cytoplasm
Explanation: The cytoplasm holds all the organelles and the cytosol in which glycolysis, protein synthesis and most other metabolic reactions proceed, so it is the general seat of cellular activity. The nucleus directs these activities and the mitochondrion supplies energy, but neither is the arena in which they take place.

Question 10

Previous-year question
The binding of a specific protein to a regulatory DNA sequence can be studied by means of [1993]
  1. a light microscope
  2. ultracentrifugation
  3. X-ray crystallography
  4. an electron microscope
Show answer
Answer: (C) X-ray crystallography
Explanation: X-ray crystallography resolves structure at the atomic level, so it can show exactly how the amino acid side chains of a regulatory protein fit into the grooves of the DNA and contact particular bases. No form of microscopy approaches this resolution, and ultracentrifugation only separates molecules by size and density.

Question 11

Previous-year question
One angstrom is equal to [1991]
  1. 0.0000001 mm
  2. 0.01 mm
  3. 0.00001 mm
  4. 0.001 mm
Show answer
Answer: (A) 0.0000001 mm
Explanation: One angstrom is 10⁻¹⁰ metre, that is one ten-thousandth of a micrometre or 0.1 nanometre. Expressed in millimetres this is 10⁻⁷ mm, or 0.0000001 mm. The unit is convenient for atomic and molecular dimensions — the diameter of the DNA double helix, for instance, is 20 Å.

Question 12

Previous-year question
A student wishes to examine cell structure under a light microscope with a 10X eyepiece and a 45X objective. Which colour of light should be used to obtain the best possible resolution? [2005]
  1. Yellow
  2. Blue
  3. Red
  4. Green
Show answer
Answer: (B) Blue
Explanation: Resolving power improves as wavelength shortens, and of the colours offered blue has the shortest wavelength, at roughly 450 nanometres against about 700 for red. Illuminating with blue light therefore allows two closely placed points to be distinguished that would merge under red light.

Question 13

Previous-year question
Resolving power is the ability to [1990]
  1. distinguish between organelles
  2. distinguish two close points
  3. magnify an image
  4. distinguish two close objects as separate
Show answer
Answer: (D) distinguish two close objects as separate
Explanation: Resolution is the smallest distance at which two adjacent objects can still be seen as distinct rather than merging into one. It is the true measure of the usefulness of a microscope, since magnifying beyond the limit of resolution enlarges the image without revealing any further detail.

Question 14

Previous-year question
The magnification of a compound microscope is NOT related to the [1989]
  1. focal length of the eyepiece
  2. numerical aperture
  3. tube length
  4. focal length of the objective
Show answer
Answer: (B) numerical aperture
Explanation: Magnification depends on the focal lengths of the objective and eyepiece and on the length of the tube separating them. Numerical aperture governs how much light the objective can gather and therefore determines resolving power, which is a quite different property — a highly magnified image may still be blurred if the numerical aperture is low.

Question 15

Which sequence correctly arranges these from the smallest to the largest typical diameter?
  1. Mycoplasma, typical bacterium, human red blood cell, typical eukaryotic cell
  2. Mycoplasma, human red blood cell, typical bacterium, typical eukaryotic cell
  3. Typical bacterium, Mycoplasma, typical eukaryotic cell, human red blood cell
  4. Typical bacterium, Mycoplasma, human red blood cell, typical eukaryotic cell
Show answer
Answer: (A) Mycoplasma, typical bacterium, human red blood cell, typical eukaryotic cell
Explanation: Mycoplasma, among the smallest cells, is about 0.3 µm across. A typical bacterium measures about 3 to 5 µm, a human red blood cell about 7 µm, and a typical eukaryotic cell about 10 to 20 µm.

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