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Chapter 1

Cell — The Structural and Functional Unit of Life

Class 10 - Selina Concise Biology Solutions


Very Short Answer Type

Question 1

Identify the cellular structures with the help of the following clues:

(a) It synthesizes the respiratory enzymes.

(b) It is made up of lipo protein.

(c) A non-living rigid layer surrounding the plasma membrane.

(d) Supportive framework for the cell.

(e) It consists of cisternae, vesicles and vacuoles.

(f) It destroys foreign substances.

(g) It gives turgidity to the plant cells.

(h) It is made up of DNA threads.

(i) It contains chromatin fibres.

(j) It initiates and regulates cell division.

Answer

(a) Mitochondria

(b) Cell membrane/plasma membrane

(c) Cell wall

(d) Endoplasmic reticulum

(e) Golgi apparatus

(f) Lysosomes

(g) Vacuoles

(h) Chromatin fibres

(i) Nucleus

(j) Centrosome

Question 2

Give two examples of each:

(a) Unicellular animals

(b) Unicellular plants

(c) Cell organelles

(d) Cell inclusions

(e) Stains which make the nucleus distinct.

Answer

(a) Unicellular animals — Amoeba, Paramoecium

(b) Unicellular plants — Chlamydomonas, Diatoms

(c) Cell organelles — Mitochondria, Nucleus

(d) Cell inclusions — Vacuoles, Granules

(e) Stains which make the nucleus distinct — Iodine, Eosin.

Question 3

Name the following:

(a) A plastid without pigment.

(b) A pigment which is not found in plastids.

(c) The orange-red pigment found in the chromoplast.

(d) Scattered Golgi complex, found in plant cells.

(e) Amoeboid blood cells of human body.

(f) The smallest cell of human body.

(g) Bean-shaped cells of stomata.

(h) The part of cytoplasm which is devoid of the organelles.

(i) The folds/finger-like projections from the inner wall of the mitochondria.

(j) The tubules of Golgi complex.

Answer

(a) Leucoplast

(b) Anthocyanin

(c) Carotene

(d) Dictyosomes

(e) White blood cells (WBCs)

(f) Red blood cells (RBCs)

(g) Guard cells

(h) Cytosol

(i) Cristae

(j) Cisternae

Descriptive Type

Question 1

Define the following terms:

(a) Cell

(b) Organelles

(c) Cytoplasm

(d) Protoplasm

(e) Nucleus

Answer

(a) Cell — Cell is the structural and functional unit of life capable of independent existence. All cells are basically alike in chemical composition and metabolic processes and arise from a pre-existing cell.

(b) Organelles — Organelles are specialized and membrane-bound, living structures in a cell concerned with definite functions.

(c) Cytoplasm — Cytoplasm is the part of the cell which is inside the cell membrane and outside the nucleus. It is a semi-liquid substance and contains several organelles, each concerned with a specific function.

(d) Protoplasm — The living parts of the cell which consist of cytoplasm, nucleus and other living bodies collectively constitute protoplasm or protoplast.

(e) Nucleus — Nucleus is a large spherical body lying nearly in the centre of the cytoplasm. It is surrounded by a double layered nuclear membrane with nuclear pores.

Question 2

Distinguish between the following pairs:

(a) Plant cell and animal cell

(b) Cell wall and cell membrane

(c) Centrosome and chromosome

(d) Chloroplast and chromoplast

Answer

(a) Plant Cell and Animal Cell

FeaturesPlant cellAnimal cell
SizeIt is usually larger in size.It is usually smaller in size.
Cell wallIt consists of a definite cell wall made up of cellulose.It lacks a cell wall.
VacuolesIt consists of large and prominent vacuoles.It consists of small and temporary vacuoles.
CytoplasmIt consists of less dense cytoplasm.It consists of denser and more granular cytoplasm.

(b) Cell Wall and Cell Membrane

Cell WallCell Membrane
It is the outermost covering in plant cells.It is the outermost covering in animal cells.
It is non-living and rigid layer.It is thin, flexible and living membrane.
It is freely permeable.It is semi-permeable.
It is made up of cellulose.It is made up of lipoproteins.

(c) Centrosome and Chromosome

CentrosomeChromosome
It is a clear space of cytoplasm located close to the nucleus.It is a highly coiled structure contained within the nucleus.
Usually one centrosome is present per cell.Several chromosomes can be present per cell.
It consists of two rod-like structures made of protein tubulin.It consists of DNA coiled around histone protein core.
It initiates and regulates cell division.It transfers hereditary characters from parents to offspring.

(d) Chloroplast and Chromoplast

ChloroplastChromoplast
It is green in colour.It is variously coloured.
It contains the pigment chlorophyll.It contains pigments such as xanthophyll and carotene.
It traps solar energy for photosynthesis.It imparts colour to flowers and fruits.
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