12. What is Prokaryotes? Give example.

sometimes it is made of RNA molecule as observed

in Tobacco mosaic virus (TMV).
Ans: Prokaryotes. These organisms have primitive and
incomplete cells. Thus, they contain prokaryotic cells 17. Draw labelled diagram of plant cell.
in their body structure. Prokaryotic cells have all three
Ans:
basic structures of a typical cell but lack nuclear
membranes around their genetic substances (DNA).

• They have single chromosome.

• Their nucleus known as Nucleoid.
• Mitochondria absent.
• Example: bacteria, cyanobacteria, blue green
algae etc.

13. What is Eukaryotes? Give example.

Ans: Eukaryotes. These have advanced and complete

cells. These cells contain membrane bound nuclei and
other cellular organelles and are called eukaryotic cells.
Example: Animal cell and plant cell.

14. How Prokaryotic cell differ from Eukaryotic cell?

18. Draw labelled diagram of Animal cell.
Ans:
Ans:

15. How Nucleus differ from Nucleoid?

Ans:

19. How Animal cell Differ from Plant cell?

Ans:

16. What is Gene?

Ans: Gene. It is a distinct unit of hereditary

information. Gene is inherited from one generation
to next and determines an observable characteristic
or trait of an organism. Genes have to carry coded
information of parents to their children or progeny,
so that children remain exactly like their parents.
Generally a gene is made of DNA molecule, but
20. Facts about cell. 22. Difference Between Diffusion And Osmosis.

• Smallest Cellular Organelle – Ribosome. Ans:

• Largest cellular organelle in plants – Plastid.
• Largest cellular organelle in animals – Mitochondria. Diffusion Osmosis
• Largest cell structure – Nucleus.
Diffusion can occur in any Osmosis occurs only in
• The thin protoplasmic projections connecting two medium liquid medium.
adjacent plant cells – Plasmodesmata.
• The connecting layer between two adjacent plant
cells – Middle lamella. The diffusing molecules It involves movement of
• The membrane of vacuole in plant cell is called may be solids, liquids or solvent molecules only
tonoplast. gases
• Mitochondria and plastids can replicate themselves
(they both have DNA and ribosomes).
• Viruses are neither prokaryotic nor eukaryotic. Semipermeable Semipermeable
• Viruses are molecular organisms. membrane is not required. membrane is required.
• Mitochondria, chloroplasts and other plastids and
nucleus have two membranes around them whereas
Golgi apparatus, endoplasmic reticulum, vacuoles and
lysosomes have single membrane. There are also
naked (without membrane) cell organelles such as 23. What is cell wall? Cell wall is made up
ribosomes, nucleolus and centriole. of ?
• In prokaryotic cells, DNA is not enclosed in a nuclear
membrane. So it is called nucleoid. Ans: A cell wall is defined as a rigid, external layer
• In prokaryotic cells, ribosomes are present but are that is specifically designed to provide structural
of smaller size (i.e., 70 S in contrast to 80 S ribosomes support and rigidity. It also keeps the interior
of eukaryotes.) components of the cell intact and safe from the
external environment.
Longest Cell: Nerve cell

Largest cell: Ostrich egg

• It is the outermost covering of the plant
cell.
• It is absent in animal cell.
21. What Is Cell theory? Who proposed cell theory? • Cell wall is rigid, strong, Thick porous and
Non-living.
Ans: Cell theory was given by a Botanist Schleiden
• Cell wall is made up of Cellulose.
(1838) and a Zoologist, Schwann (1839).

Cell Theory: 24. Write the functions of Cell wall.

Thus, the cell theory comprises of the following • The plant cell wall provides definite shape,
postulates : strength, rigidity
1. All organisms are composed of cells and cell • It also provides protection against
products (e.g., secretions). mechanical stress and physical shocks
2. cells are structural and functional units of life.
• It helps to control cell expansion due to the
3. All cells arise from pre-existing cells only. intake of water
4. Every organism starts its life as a single cell. Viruses • Also helps in preventing water loss from the
are an exception to cell theory cell
• It is responsible for transporting substances
between and across the cell
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• It acts as a barrier between the interior
Agartala, Ranirbazar cellular components and the external
environment
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25. What is plasmolysis? component of the cell wall, in bacteria the primary
component of the cell wall is peptidoglycan and in fungi the
Ans: When a living plant cell loses water through primary component of the cell wall is chitin.
osmosis, there is a shrinkage or contraction of the 33. Write The Differences between cell wall and animal
protoplasm away from the cell wall. This phenomenon is plasma membrane.
called plasmolysis.
Ans:
26. What is cell membrane or plasma membrane?

Ans: Plasma membrane is a living, thin, delicate, elastic,

selectively permeable membrane, it is about 7nm thick. It
is made up of phospholipids. It is present in both plant
and animal cell.

27. Why plasma membrane is called selectively

permeable membrane?

Ans: Plasma membrane is called selectively permeable

membrane because it allows the movement of only
selected molecules across it and not all of
them.

28. What would happen if the plasma membrane ruptures

or breaks down?
Ans: If plasma membrane ruptures or breaks down then 33. Draw the labelled diagram of nucleus? Briefly discuss the
molecules of some substances will freely move in and out of structure and function.
the cells. As plasma membrane acts as a mechanical barrier, Ans:
exchange of material from its surroundings through osmosis
or diffusion in a cell won’t take place. Consequently, the cell
would die due to the disappearance of the protoplasmic
material.
29.Write Function of Plasma membrane.

Ans: The main functions of the cell membrane include:

1. Protecting the integrity of the interior cell.

2. Providing support and maintaining the shape of the

cell.

3. Helps in regulating cell growth through the balance

of endocytosis and exocytosis.

4. The cell membrane also plays an important role

in cell signalling and communication.
Nucleus: The nucleus is a double-membraned organelle that
5. It acts as a selectively permeable membrane by contains the genetic material and other instructions required
allowing the entry of only selected substances into for cellular processes. It is exclusively found in eukaryotic
the cell. cells and is also one of the largest organelles.
30. Are cell walls and cell membranes the same thing? Structure of nucleus:
Ans: Cell walls are distinctly different from cell membranes.
For instance, the cell wall is present only in plants, fungi and • A double-membraned organelle known as the
some bacteria. The cell membrane, on the other hand, is nuclear membrane/envelope engirdles the nucleus.
present in all living organisms including plants.
• The nucleolus is found within the nucleus, occupying
25% per cent of the volume.

31. What is the role of the plasma membrane?

• Thread-like, dense structures known as chromatins
are found within the nucleus containing proteins and
Ans: The cell membrane is also called the plasma membrane. DNA.
It provides protection for the cell and its cellular components • The mechanical strength for the nucleus is provided
from the external environment. It is selectively permeable and by the nuclear matrix, a network of fibres and
regulates the movement of molecules in and out of the cell. filaments which performs functions similar to the
32. What is the primary component of the cell wall? cytoskeleton.
• The cell’s chromosomes are also confined within it.
Ans: The primary component of the cell wall varies with
different organisms. In the plant cells, cellulose is the primary • DNA is present in the Chromosomes.

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Functions of the Nucleus? ER occurs in three forms : cisternae (i.e., closed, fluid-filled
sacs), vesicles and tubules.
• It is responsible for storing the cell’s hereditary
material or the DNA. It is of two types :

• It is responsible for coordinating many of the Rough endoplasmic reticulum (RER) : with ribosomes
important cellular activities such as protein attached on its surface for synthesizing proteins.
synthesis, cell division, growth and a host of
other important functions. Smooth endoplasmic reticulum (SER) : which is without
• It regulates the cell cycle. ribosomes and is meant for secreting lipids.

• It is concerned with the transmission of

42. Write Functions of ER?
hereditary traits from the parents to offspring.

Ans: Functions :
34. Which organelles is called brain of the cell why?
1. It forms supporting skeletal framework of the cell.
2. ER provides a pathway for the distribution of nuclear
Ans: The nucleus directs and regulates the cell's functions
material from one cell to the other.
(such as development and metabolism) and houses the
genes, which hold the cell's genetic information. Hence, due 3. Certain enzymes present in smooth ER synthesize fats
to these functions of a nucleus it is called the brain of the cell. (lipids), steroids and cholesterol.
4. Rough ER is concerned with the transport of proteins
35. Who discovered nucleus? which are syntehsized by ribosomes on their surface

Ans: Robert Brown. *****[ Fact: The ER is absent in Red Blood Cell (RBC) in
mammals. The Nucleus is absent in RBC ]
36. Which structure is called little nucleus?

Ans: Nucleolus. 43. Write The differences between RER and SER?

37. Differences between Nucleus and Nucleolus. Ans:

Ans:

38.Differentiate between chromatin and

chromosome.
Ans. Chromatin is the nucleoprotein (DNA +protein)
fibrous mass which stains strongly with basic dyes and is
present inside nucleus.

Chromosome is a thread -like, stainable, condensed

chromatin unit, visible at cell division. Both chromatin
and chromosomes contain hereditary information in
the form of genes.

39. Which molecules are present in chromatin.

Ans. DNA, histone proteins and acids proteins.

40. Why is nucleus called director of the cell ?

Ans. Nucleus controls and coordinates all the metabolic
functions of the cell.

41. What is Endoplasmic Reticulum (ER) ?

Ans: Inside the cell there exists a membranous network

enclosing a fluid-filled lumen which almost fills up the
intracellular cavity. It is called endoplasmic reticulum
(ER). At one end ER is connected to the outer membrane of
the nucleus and at the other end to the plasma membrane.

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