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NCERT Exemplar · Class 9 Science The Fundamental Unit of Life

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Multiple Choice Questions 1–10 (part 1 of 6)

  1. Exercise 1

    Which of the following can be made into crystal?
    (a)
    A Bacterium
    (b)
    An Amoeba
    (c)
    A Virus
    (d)
    A Sperm

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    NCERT’s answer
    (c)
    (c) A Virus.Outside a host cell it is an inert particle of protein and nucleic acid, so it crystallises like a chemical compound; a bacterium, Amoeba or sperm, being alive, cannot.

  2. Exercise 2

    A cell will swell up if
    (a)
    The concentration of water molecules in the cell is higher than the
    concentration of water molecules in surrounding medium
    (b)
    The concentration of water molecules in surrounding medium is higher
    than water molecules concentration in the cell
    (c)
    The concentration of water molecules is same in the cell and in the
    surrounding medium
    (d)
    Concentration of water molecules does not matter

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    NCERT’s answer
    (b)
    (b) The concentration of water molecules in the surrounding medium is higher than in the cell.\[c_{\text{water(outside)}} > c_{\text{water(inside)}} \Rightarrow \text{net osmotic influx} \Rightarrow \text{cell swells} \]The reverse difference, option (a), would draw water out and shrink the cell instead.

  3. Exercise 3

    Chromosomes are made up of
    (a)
    DNA
    (b)
    protein
    (c)
    DNA and protein
    (d)
    RNA

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    NCERT’s answer
    (c)
    (c) DNA and protein.A chromosome is a chromatin thread condensed for division: the DNA carries the genetic instructions, and histone proteins coil and package it.

  4. Exercise 4

    Which of these options are not a function of Ribosomes?
    (i)
    It helps in manufacture of protein molecules
    (ii)
    It helps in manufacture of enzymes
    (iii)
    It helps in manufacture of hormones
    (iv)
    It helps in manufacture of starch molecules
    (i)
    and (ii)
    (ii)
    and (iii)
    (iii)
    and (iv)
    (iv)
    and (i)

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    NCERT’s answer
    (c)
    (c) (iii) and (iv).Ribosomes make proteins, so structural proteins (i) and enzymes (ii) are covered. Many hormones are steroids, not ribosomal products, and starch is a carbohydrate, not a ribosome product.

  5. Exercise 5

    Which of these is not related to endoplasmic reticulum?
    (a)
    It behaves as transport channel for proteins between nucleus and
    cytoplasm
    (b)
    It transports materials between various regions in cytoplasm
    (c)
    It can be the site of energy generation
    (d)
    It can be the site for some biochemical activities of the cell

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    NCERT’s answer
    (c)
    (c) It can be the site of energy generation.That is the mitochondrion's role. The endoplasmic reticulum instead transports proteins and materials through the cytoplasm and hosts several biochemical activities.

  6. Exercise 6

    Following are a few definitions of osmosis
    Read carefully and select the correct definition
    (a)
    Movement of water molecules from a region of higher concentration to
    a region of lower concentration through a semipermeable membrane
    (b)
    Movement of solvent molecules from its higher concentration to lower
    concentration
    (c)
    Movement of solvent molecules from higher concentration to lower
    concentration of solution through a permeable membrane
    (d)
    Movement of solute molecules from lower concentration to higher
    concentration of solution through a semipermeable membrane

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    NCERT’s answer
    (a)
    (a) Water moves from higher to lower concentration through a semipermeable membrane.Option (b) omits the membrane, (c) says merely permeable, and (d) wrongly moves solute, not water.

  7. Exercise 7

    Plasmolysis in a plant cell is defined as
    (a)
    break down (lysis ) of plasma membrane in hypotonic medium
    (b)
    shrinkage of cytoplasm in hypertonic medium
    (c)
    shrinkage of nucleoplasm
    (d)
    none of them

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    NCERT’s answer
    (b)
    (b) Shrinkage of cytoplasm in a hypertonic medium.\[\text{hypertonic medium} \Rightarrow \text{net osmotic efflux of water} \Rightarrow \text{protoplast shrinks} \]This rules out (a) lysis in a hypotonic medium, and (c) since it is the cytoplasm, not the nucleoplasm, that shrinks.

  8. Exercise 8

    Which of the following are covered by a single membrane?
    (a)
    Mitochondria
    (b)
    Vacuole
    (c)
    Lysosome
    (d)
    Plastid

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    NCERT’s printed answer for this exercise does not match its own question. This working follows the question as printed.

    (b) and (c) -- vacuole and lysosome, both single-membrane organelles: the tonoplast bounds the vacuole, a Golgi-derived membrane bounds the lysosome. Mitochondria and plastids carry two membranes each.Answer: (b) and (c).NCERT prints: (b) — but the lysosome is single-membraned too (a Golgi-derived membrane), and the stem asks which "are" covered by one membrane, so (c) belongs beside (b).

  9. Exercise 9

    Find out the false sentences
    (a)
    Golgi apparatus is involved with the formation of lysosomes
    (b)
    Nucleus, mitochondria and plastid have DNA; hence they are able to
    make their own structural proteins
    (c)
    Mitochondria is said to be the power house of the cell as ATP is
    generated in them.
    (d)
    Cytoplasm is called as protoplasm

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    NCERT’s printed answer for this exercise does not match its own question. This working follows the question as printed.

    (b) and (d) are false.Protoplasm is cytoplasm plus nucleus \(\displaystyle \Rightarrow\) (d) false. Only mitochondria and plastids, with their own ribosomes, make some structural proteins; the nucleus does not \(\displaystyle \Rightarrow\) (b) false. (a) and (c) are correct.NCERT prints: (a) — but (a) states a true fact, that the Golgi apparatus forms lysosomes, so it cannot be among the false sentences the question asks for.

  10. Exercise 10

    Find out the correct sentence
    (a)
    Enzymes packed in Lysosomes are made through RER (rough
    endoplasmic reticulum)
    (b)
    Rough endoplasmic reticulum and smooth endoplasmic reticulum
    produce lipid and protein respectively
    (c)
    Endoplasmic reticulum is related with the destruction of plasma
    membrane
    (d)
    Nucleoid is present inside the nucleoplasm of eukaryotic nucleus
    THE FUNDAMENTAL UNIT OF LIFE

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    NCERT’s answer
    (a)
    (a) Enzymes packed in lysosomes are made through RER.
    (b)
    reverses the RER/SER products, (c) wrongly links ER to membrane destruction, and (d) confuses the nucleoid, a prokaryotic feature, with the eukaryotic nucleus.