YASH
CLASSES
THE FUNDAMENTAL UNIT OF LIFE
Q. 1. What is eukaryotic cell ?
Ans. A
cell that contains membrane bound organelles in
its cytoplasm is called Eukaryotic
cell. A eukaryotic
cell has definite nucleus with nuclear
membrane.
Q.2.What is nucleoid?
Ans.
Nucleoid. It is the nuclear region that contains a
single chromosome which is in direct contact
with
cytoplasm. Nucleoid is found in a
prokaryotic cell.
Q.3. Give two examples of prokaryotic
organisms.
Ans.
Bacteria and Cyanobacteria (earlier called blue green
algae) e.g., Nostoc are prokaryotic
unicellular organisms.
Q.4. What is a prokaryotic cell ?
Ans. A
cell which lacks nuclear membrane, contain a single
chromosome and also lacks membrane bound
organelles.
Q.5. What is cytoplasm?
Ans. The
part of protoplasm which remains after excluding
nucleus,
is known as cytoplasm. Cytoplasm contains
an aggregate molecule of various chemical
and cell
organelles. Most of the biochemical
reactions such as
protein synthesis, release of energy etc. take place in
cytoplasm or organelles present in the
cytoplasm.
Q.6. List four major functions of a
cell.
Ans. Functions of Cell:
(1) Synthesis of substances.
(2) Digestion (lysis) of substances.
(3)
Generation of energy for vital functions.
(4)Secretion.
Q.7.Differentiate between prokaryotic cell and eukaryotic cell.
Ans.
Prokaryotic
Cell Eukaryotic Cell
1.
Cell size is generally small 1. Cell is generally large
(1-10 µm) (5-100 µm)
2. Nuclear region called 2. Nuclear material
is surrounded
nucleoid and not surrounded by a nuclear membrane.
by a nuclear membrane
3. Only a single chromosome 3. More than one
chromosome
is present. are present.
4. Nucleolus is absent. 4. Nucleolus is present.
5. Membrane bound cell 5. Cell organelles
bounded
organelles are absent. by membrane are
present.
6. Cell division by fission or 6. Cell division mitotic or meiotic.
budding (no mitosis).
INTEXT BOOK QUESTIONS
Q.1.Who discovered the cell and how ?
Ans-
Robert Hook (1665), Robert Hook by chance observe a
slice of Cork through a self-designed
microscope. He
observed that it contains many little
compartments,
like a honeycomb, which he named as
cell.
Q.2. Why is the cell called structural and
functional unit of life?
Answer. Some organisms like Amoeba are
unicellular and have single
body. The single cell of unicellular from
performs all the live
process. Multicellular Organism have many
cells to perform different
function. Thus, cell is the structural unit
of all living organisms. Each
living cell perform certain basic function
that are arrested of all living
forms such as cellular respiration. All cell
has same organised no matter
that their function. is same thus cell is
also functional unit of life.
or
The cell is called the structural and
functional unit of life because:
Structural Unit:
1. Basic building block: Cells are the smallest
units of life, and all living
organisms are composed of one or more
cells.
2. Organization: Cells provide the structural
framework for tissues, organs,
and systems, allowing for organization
and complexity.
3. Membrane-bound: Cells have a defined boundary,
the plasma membrane,
which separates the cell from its
environment.
Functional Unit:
1. Metabolic
processes: Cells carry out essential metabolic functions,
such as energy production, nutrient uptake,
and waste removal.
2. Genetic information: Cells contain genetic
material (DNA/RNA)
that stores and transmits genetic
information.
3. Response to stimuli: Cells respond to internal and
external stimuli,
adapting to changes in their environment.
4. Growth and reproduction: Cells grow, divide, and
reproduce,
allowing organisms to grow, repair, and
reproduce.
5. Specialization: Cells differentiate and specialize
to perform
unique functions, enabling complex life
processes.
In summary, cells provide the structural
framework and functional capabilities necessary for life, making them the
fundamental units of life.
Q.3.
How do substances like CO2, and water move in and out of the cell?
Discuss .
Ans. When concentration of CO2, is more inside
than outside, CO2,
diffuses from the cell to outside of
cell. If CO2, concentration
inside the cell in less, CO2,
inside the cell from outside.
The water moves in and out of the cell
by the process of Osmosis,
Osmosis is the passage of water fr of
hi water
concentration
through semi-permeable membrane (cell membrane)
to a region of low concentration
water.
or
Ans- substances like CO2 and water
are move in and out of the cell
CO2:
- Diffusion: CO2 moves out of
cells through diffusion, a passive process where molecules move from an area of high
concentration to an area of low concentration.
- Facilitated diffusion: CO2 can
also use transport proteins to facilitate its
movement out of cells.
Water
- Osmosis:
Water moves into or out of cells through osmosis, a process
where water molecules move from an area of
high concentration to an area
of low concentration through a selectively
permeable membrane.
- Aquaporins: Water can also use specialized
transport proteins called aquaporins to move in and out of cells.
Other transport mechanisms:
- Active transport: Cells use energy to
transport substances against their concentration gradient.
- Passive transport: Substances move down their
concentration gradient without energy input.
- Endocytosis and exocytosis: Cells use vesicles
to transport substances in and out through endocytosis (inward) and exocytosis
(outward).
Cells
regulate the movement of substances like CO2 and water to maintain homeostasis,
respond to changes in their environment, and perform various cellular
functions.
Q.4.Why is the
plasma membrane called a selectively permeable
membrane?
Ans- Plasma membrane permits the entry and exit
of some materials in the cell while it also prevents movement of some other
materials. So, it is called selectively permeable membrane.
or
The plasma
membrane is called a selectively permeable membrane because it allows certain
substances to pass through while restricting others. This means that it is:
1. Permeable: Allows
certain substances to pass through.
2. Selective:
Chooses which substances to allow through based on their size, charge,
polarity, and other properties.
The plasma membrane is
selectively permeable due to its structure:
1. Phospholipid bilayer: The membrane's
phospholipid molecules have hydrophilic (water-loving) heads and hydrophobic
(water-fearing) tails, creating a barrier for polar molecules.
2. Embedded proteins: Transport proteins and
channels allow specific substances to pass through, while restricting others.
3. Lipid rafts: Specialized regions of the
membrane with unique lipid and protein composition, which can regulate
permeability.
This selective
permeability allows cells to:
1.
Regulate what enters and leaves the cell.
2.
Maintain a stable internal environment (homeostasis).
3. Respond
to signals and changes in the environment.
In
summary, the plasma membrane's selective permeability is crucial for cellular
function, allowing cells to control the movement of substances and maintain
their internal environment.
5. Fill in the gaps in the following table illustrating
differences between prokaryotic and eukaryotic cells.
Ans. Prokaryotic Cell
Eukaryotic Cell
1.
Size: generally small 1. Size: generally
(1-10 μm) 1 µm = 10-6 m large (5-100 μm)
2. Nuclear region:
is poorly 2. Nuclear
region: well-defined
defined due to absence and surrounded
of a
nuclear membrane by a nuclear membrane.
and
known as nucleoid.
3. Chromosome: single 3. More than one
chromosome.
4. Membrane-bound cell 4. Membrane bound cell
organelles absent. organelles are
present.
Q.6. Can you name
the two organelles we have studied
that contain their own genetic
Ans. a. Mitochondria and b. Plastid (chloroplast).
Q7. The
organisation of a cell is destroyed due to some
physical or chemical influence, what will
happen?
Ans. Each cell has got certain specific cell organelles.
Each cell
organelle performs a special
function, e.g., making of new
material, removal waste from the
cell, release of energy etc.
If the organization of a cell is destroyed,
the functioning of
the cell organelle will be disturbed,
control of the nucleus
will be lost. Ultimately cell die.
Q.8.Why are lysosomes known as suicide bags?
Ans. A
Lysosome is membrane bound bag like which contains
powerful enzymes. If lysosome
burst, its enzymes eat up
(digest) other organelles of its own cell. Therefore,
they are
known as 'suicide bags'.
Q.9. Where are proteins synthesised inside the cell?
Ans. Ribosomes.
Exercise
Q.1. Make a comparison
and write down ways in which plant cells are
different from animal cells?
Ans. Plant Cell Animal Cell
1. The outermost covering of the
1. The outermost
covering is
plant cell is the cell wall
which the plasma
membrane.
is formed of cellulose.
2. Plastids (e.g., chloroplast) present. 2. Plastids
absent.
3. Large vacuole present. 3. No or small vacuoles are present.
4. Centrioles are absent but polar 4. Centrioles
are present within
caps are present. centrosome.
5. Golgi
apparatus is in the form of 5. Prominent and highly complex
of sub-units, called dictyosomes. Golgi apparatus is present near
nucleus.
Q.2. How is a prokaryotic cell different
cell ?
Ans. Prokaryotic Cell
Eukaryotic Cell
1. Size: generally small 1. Size: generally
(1-10
μm) 1 µm = 10-6 m large (5-100 μm)
2. Nuclear region: is poorly 2. Nuclear region: well-defined
defined due to absence and surrounded
of a nuclear membrane by a nuclear membrane.
and known as nucleoid.
3. Chromosome: single 3. More than one chromosome.
4. Membrane-bound cell 4. Membrane bound cell
organelles absent. organelles are
present.
5. Cell division by fission or 5. Cell division mitosis or meiotic.
budding ( no
mitosis)
Or
Prokaryotic cells and eukaryotic cells are two types of cellular life forms that differ significantly in their structure, organization, and functionality. Here are the main differences:
Prokaryotic
Cells:
1.
Lack a true nucleus (genetic material is in a single circular chromosome)
2.
Small size (typically 1-5 μm)
3.
Simple cell structure (no membrane-bound organelles)
4.
No mitochondria (generate energy through cell membrane)
5.
No chloroplasts (photosynthesis occurs in the cell membrane)
6.
Fast reproduction (binary fission)
7.
Found in bacteria and archaea
Eukaryotic Cells:
1. Have a true nucleus (genetic
material is in linear chromosomes)
2. Larger size (typically 10-100 μm)
3. Complex cell structure
(membrane-bound organelles)
4. Mitochondria present (generate
energy)
5. Chloroplasts present (photosynthesis
occurs in chloroplasts)
6. Slower reproduction (mitosis and
meiosis)
7. Found in plants, animals, fungi, and
protists
Additionally, eukaryotic cells have:
- A cytoskeleton for structural
support
- A Golgi apparatus for protein
modification
- Lysosomes for cellular digestion
- Endoplasmic reticulum for protein
synthesis and transport
These differences reflect the unique
characteristics and capabilities
of each cell type, with prokaryotic cells
being simpler and more
primitive, and eukaryotic cells being more
complex and specialized.
Q.3. What happened if the plasma membrane ruptures or
breaks down?
Ans. If the
plasma membrane ruptures or breaks down, the cell's
internal environment is disrupted, leading to:
1. Loss of cellular contents:
Cytoplasm, organelles, and genetic
material leak out.
2. Uncontrolled movement of substances:
Ions, water, and molecules flow in and out, disrupting cellular balance.
3. Cellular swelling: Water rushes in,
causing the cell to swell and potentially burst.
4. Disruption of cellular processes:
Metabolic reactions, protein synthesis, and signalling pathways are impaired.
5. Cell death: If the damage is severe,
the cell may undergo apoptosis (programmed cell death) or necrosis
(uncontrolled cell death).
Consequences of plasma membrane breakdown:
1. Infection: Bacteria, viruses, and toxins can enter the cell.
2.
Inflammation: Cellular contents leak out, triggering an immune response.
3.
Tissue damage: Nearby cells and tissues may be affected.
4.
Disease: Membrane breakdown can contribute to diseases like cancer,
Alzheimer's, and Parkinson's.
5.
Cell lysis: The cell bursts, releasing its contents, which can lead to tissue
damage and inflammation.
Ans. Cells have repair mechanisms, such as membrane resealing and patching, to mitigate damage. However, severe or prolonged membrane breakdown can lead to irreversible damage and cell death.
Q.4.What would happen if the life of a cell if there is no
Golgi apparatus?
Ans. Golgi
apparatus package and distich enzymes, hormones
and other essential proteins and lipids
secreted by ER to target
inside and outside of the cell.
Moreover, the digestive enzymes which remain
concealed in
lysosome , will remain free in the
cytoplasm killing the other
cell content .
overall in absence of Golgi apparatus cell would
die.
Q.5. Which organelle is known as the powerhouse of the cell ?
Ans. Mitochondria are known as Power House of
the cell. They
are said en because, the energy
required for various life activities
is released by mitochondria in the
form of ATP molecules.
The body uses energy stored in ATP
for synthesis of new
compounds and for mechanical work.
As ATP instantly provide
energy, they are called energy
currency of the cell.
Q.6. Where do the lipids and proteins constituting the cell
membrane gets synthesised?
Ans. Rough Endoplasmic
Reticulum (RER)-synthesizes proteins
constituting
cell membrane .
Smooth Endoplasmic Reticulum
(SER)-secrete lipids
constituting cell membrane.
Q. 7. How does an Amoeba obtain its food ?
Ans.
Amoeba has flexible cell membrane. It enables amoeba to
engulf in food by the process called
endocytosis,
Q. 8. What is osmosis ?
Ans.
The passage of water from a region of its high concentration
through a semipermeable membrane to a region
of low water
concentration is known as osmosis.
Q. 9. Carry out the following osmosis experiment:
Take
four peeled potato halves and scoos each one out to make potato cups. One of
these potato cups should be made from a boiled potato. Put each potato cup in a
trough containing water. Now,
(a)
keep cup A empty
(b)
put one teaspoon sugar in cup B
(c)
put one teaspoon salt in cup C
(d)
put one teaspoon sugar in bolled potato cup D.
Keep these for two hours. Then observe the
four potato cups and
answer the following
(i) Explain why water gathers in the hollowed portion of B and C
(ii)
Why is potato A necessary for this experiment ?
(iii) Explain why water does not gather in the hollowed-out
portions
of A and D.
Ans. (a) Water gathers in the hollowed portion of potato B and C because
Living plasma membrane of potato cup act as semipermeable membrane.
(ii) There is higher concentration of water in trough than the sugar solution of B and salt solution of C potato cup respectively.
(iii) So, by process of osmosis water moves into potato cups B and C.
(b)Potato cup A is kept empty to act as control. This shows that osmosis
occurs only when a solution with low
concentration of water in
separated by semipermeable cell membrane from
the region of
higher concentration of water.
(c) (i) In the potato cup A, there is no solution to cause osmosis to occur.
In the potato cup D, the potato cell membrane lost quality of semi
permeability due to boiling. So, no water
movement occurs from the
trough water into the potato cup D.