CBSE Guide for Class 8, Ncert Science
Cell - Structure and Functions
CBSE Guide - CBSE Guess - CBSE Sample Questions
CBSE Sample Questions with Short Answers
Question.1: Define Prokaryotes and Eukaryotes.
Answer:
Prokaryote: The cells having nuclear material
without nuclear membrane are termed as prokaryotic cells. An organism with
these kinds of cells is called a Prokaryote e.g. Bacteria and Blue Green Algae.
Eukaryote: The cells having well organized
nucleus with a nuclear membrane are termed as eukaryotic cells. All organisms
other than Bacteria and Blue Green Algae are Eukaryotes.
Question.2: What is Protoplasm?
Answer: The entire content of a living cell
is known as protoplasm. It includes
cytoplasm and the nucleus.
Question.3: Give three examples of unicellular organisms.
Answer: Amoeba, Paramecium and Chlamydomonas.
Question.4: Name the cell organelle which is found only in plant cell.
Answer: Plastids.
Question.5: What is the smallest cell size?
Answer: The smallest cell is 0.1 to 0.5
micrometer in Bacteria.
Question.6: What is the largest cell?
Answer: The largest cell is 170mm x 130mm, is
the egg of an Ostrich.
CBSE Sample Questions with Long Answers
Question.7: Why cell is known as structural and functional unit of life?
Answer: Refer to the answer of Q.No.8 (NCERT
Textbook Exercise) above.
Question.8: Why are the mitochondria known as the power house of the
cell?
Answer: Mitochondria
are rod shaped and very minute bodies present in cytoplasm. They are concerned
with release of energy from food during respiration. Because of this they are
often referred to as the power house of the cell.
Question.9: Why plasma membrane is called a selectively permeable
membrane?
Answer: A cell bound by a semi-permeable
membrane called plasma membrane that enables it to exchange only certain
materials with its surroundings. Plasma membrane permits the entry and exit of
some material in the cell. It also prevents movement of some other material.
Therefore, ‘Plasma Membrane’ is
called as ‘selectively permeable membrane’.
Question.10: Write a short note on the ‘shape of cells’ or ‘cell shape’.
Answer: Cells exhibit a variety of shapes.
Some cells have a definite shape while some keep on changing its shape. For
example- White Blood Cell (WBC) present in our bodies, Amoeba continuously
changes their shape. However, most of the cells maintain a constant shape and
the different shapes are related to their specific functions. For example-
blood cells are spherical, muscle cells have spindle shape, and nerve cells are
long and branched. It is mainly the cell membrane which provides the shape to the
cells of plants and animals.
Question.11: Write short notes on the following:
(a)
Gene
(b)
Chromosomes
(c)
Organelles
(d)
Vacuole
(e)
Tissues
(f)
Plastids.
Answer:
(a)
Gene: Gene is a unit of inheritance in
living organisms. Nucleus contains thread-like structures called chromosomes
which carry genes in them. Genes are composed of DNA (Deoxyribonucleic acid), except in some viruses. They achieved their
effects by directing the synthesis of proteins.
(b)
Chromosome: These are the microscopic
thread-like parts present in the nucleus of a cell that carries hereditary
information in the form of genes.
(c) Organelles: The various tiny components of a
cell present in the cytoplasm are known as organelles. These are - Mitochondria, Golgi bodies, Ribosome
etc.
(d)
Vacuole: A vacuole is a clear space generally
stored in the cytoplasm. Big size vacuole is found in the plant cell whereas;
in animal cells they are very small. In protozoa, vacuoles are cytoplasmic
organs performing many functions such as digestion, excretion etc.
(e)
Tissues: Each organ is further made up of
smaller parts called tissues. A tissue is a group of similar cells performing a
specific function.
(f) Plastids: Plastids are found in the plant
cells but are absent in animal cells. They are found scattered in the cytoplasm
of the leaf cells. Plastids are of three types -
1.
Chloroplast
2.
Leucoplast
and
3.
Chromoplast
Among
these three types chloroplast is the most important as they contain chlorophyll
which is a necessary element for photosynthesis. Because of this reason
plastids are also said as ‘Kitchen of plant cells’.
Question.12: Why Plastids are said as ‘Kitchen of plant cells’?
Answer: See the answer of the Q.No.5 (f).
Question.13: Differentiate between Plant cell and animal cell.
Answer: The differentiation between plant and
animal cells is given in the following table:
Animal Cell
|
Plant Cell
|
(a) Cell wall
is absent.
(b) These cells
do not contain Chloroplasts.
(c) Chromosomes
are present in the nucleus.
(d) Vacuoles
are less and of smaller size.
|
(a) Plant cells have rigid cell walls.
(b) Chloroplasts are present.
(c) Chromosomes are present.
(d) Vacuoles are larger and more in
numbers.
|
Question.14: Write a short note on ‘Nucleus of a cell’?
Answer: Refer to the answer of Q.No.3 (b) of Solutions
of Ncert Cbse Science, Chapter 8 Cell - Structure and Functions: Exercise
Questions at
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