Question 1:
Who discovered cells and how?
Answer:
Cells were discovered in 1665 by an English Botanist,
Robert Hooke. He used a primitive microscope to observe
cells in a cork slice.
Question 2:
Why is the cell called the structural and functional unit of
life?
Answer:
Cells constitute various components of plants and
animals. A cell is the smallest unit of life and is capable
of all living functions. Cells are the building blocks of life.
This is the reason why cells are referred to as the basic
structural and functional units of life. All cells vary in their
shape, size, and activity they perform. In fact, the
shape and size of the cell is related to the specific
functions they perform.
–
Question 1:
How do substances like CO2 and water move in and out of
the cell? Discuss.
Answer:
The cell membrane is selectively permeable and regulates
themovement of substances in and out of the
cell. Movement of CO2:
CO2 is produced during cellular respiration. Therefore, it is
present in high concentrations inside the cell. This CO2
must be excreted out of the cell. In the cell’s external
environment, the concentration of CO2 is low as
compared to that inside the cell. Therefore, according to
the principle of diffusion, CO2 moves from a region
of higher concentration (inside the cell) towards a region
of lower concentration (outside the cell). Similarly, O2
enters the cell by the process of diffusion when
the concentration of O2 inside the cell is low as
compared to its surroundings.
Movement of water:
Water moves from a region of high concentration to a
region of low concentration through the plasma
membrane. The plasma membrane acts as a semi-
permeable membrane, and this movement of water is
known as osmosis. However, the movement of water
across the plasma membrane of the cell is affected by
the amount of substance dissolved in water.
Question 2:
Why is the plasma membrane called a selectively
permeable membrane?
Answer:
Thecell membraneor the plasma membraneis known as a
selectively permeable membrane because it regulates the
movement of substances in and out of the cell. This
means that the plasma membrane allows the entry of only
some substances and prevents the movement of some
other materials.
–
Question 1:
Fill in the gaps in the following table illustrating
differences between prokaryotic and eukaryotic cells.
–
Question 1:
Can you name the two organelles we have studied that
contain their own genetic material?
Answer:
Mitochondriaandplastids are the two organelles that
contain their own genetic material. Both these organelles
have their own DNA and ribosomes.
Question 2:
If the organisation of a cell is destroyed due to some
physical or chemical influence,
what will happen?
Answer:
Cell is the smallest unit of life, which is capable of all
living functions. If the organisation of a cell is destroyed
due to some physical or chemical influence, then the
ability of the cell to perform all living functions such as
respiration, nutrition, excretion, etc. would be affected.
Question 3:
Why are lysosomes known as suicide bags?
Answer:
Lysosomes are membrane-bound vesicular structures that
contain powerful digestive enzymes. These enzymes are
capable of breaking down any foreign food particle
or microbes entering the cell. Sometimes, lysosomes can
cause self-destruction of a cell by releasing these
digestive enzymes within the cells. Hence, they are also
known as ‘suicidal bags’.
Question 4:
Where are proteins synthesized inside the cell?
Answer:
Ribosomesare the site for protein synthesis. Ribosomes
are very small structures found either in a free state,
suspended in the cytoplasm, or attached to the surface of
the endoplasmic reticulum. They are composed of
ribonucleic acids and proteins.
–
Question 1:
Make a comparison and write down ways in which plant
cells are different from animal cells.
Answer:
Question 2:
How is a prokaryotic cell different from a eukaryotic cell?
Answer:
Question 3:
What would happen if the plasma membrane ruptures or
breaks down?
Answer:
If the plasma membrane of a cell is ruptured, then the cell
will die. The plasma membrane regulates the movement of
substances in and out of the cell by diffusion or osmosis.
Thus, if the plasma membrane is ruptured, then the cell
might leak out its contents.
Question 4:
What would happen to the life of a cell if there was no
Golgi apparatus?
Answer:
If there was no Golgi apparatus in the cell, then most
activities performed by the Golgi apparatus will not take
place.
(i) Membranes of the Golgi apparatus are often connected
to ER membranes. It collects simpler molecules and
combines them to make more complex molecules. These
are then packaged in small vesicles and are either stored
in the cell or sent out as per the requirement. Thus, if the
Golgi apparatus is absent in the cell, then the above
process of storage, modification, and packaging of
products will not be possible.
(ii) The formation of complex sugars from simple sugars
will not be possible as this takes place with the help of
enzymes present in Golgi bodies.
(iii) The Golgi apparatus is involved in the formation of
lysosomes or peroxisomes. Thus, if the Golgi body is
absent in a cell, the synthesis of lysosomes or
peroxisomes will not be possible in the cell.
Question 5:
Which organelle is known as the powerhouse of the cell?
Why?
Answer:
Mitochondriaare known as the powerhouse of cells.
Mitochondria create energy for the cell, and this process
of creating energy for the cell is known as
cellular respiration. Most chemical reactions involved in
cellular respiration occur in the mitochondria. The energy
required for various chemical activities needed for life
is released by the mitochondria in the form of ATP
(Adenosine triphosphate) molecules. For this reason,
mitochondria are known as the powerhouse of cells.
Question 6:
Where do the lipids and proteins constituting the cell
membrane get synthesized?
Answer:
Lipids and proteinsconstituting the cell membrane are
synthesized in the endoplasmic reticulum.
SER (Smooth endoplasmic reticulum) helps in the
manufacturing of lipids.
RER (Rough endoplasmic reticulum) has particles attached
to its surface, called ribosomes. These ribosomes are the
site for protein synthesis.
Question 7:
How does an Amoeba obtain its food?
Answer:
Amoebaobtains its food through the process of
endocytosis. The flexibility of the cell membrane enables
the cell to engulf the solid particles of food and other
materials from its external environment.
Question 8:
What is osmosis?
Answer:
The movement of water molecules from a region of high
concentration to a region of low concentration through a
selectively permeable membrane is called osmosis. It is a
special case of diffusion, where the medium is water.
For example, if the medium surrounding the cell has a
higher water concentration than the cell i.e., if the
solution is a dilute solution, then the cell will gain water
by osmosis.
Movement of water inside the cell
Question 9:
Carry out the following osmosis experiment: Take four
peeled potato halves and scoop 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 the boiled 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.
Answer Discussion
Experimental set up
(i) Water gathers in the hollowed portions of set-up B and
C because water enters the potato as a result of osmosis.
Since the medium surrounding the cell has a higher water
concentration than the cell, the water moves inside by
osmosis. Hence, water gathers in the hollowed portions of
the potato cup.
(ii) Potato A in the experiment acts as a control set-up.
No water gathers in the hollowed portions of potato A.
(iii) Water does not gather in the hollowed portions of
potato A because potato cup A is empty. It is a control
set-up in the experiment. Water is not able to enter potato
D because the potato used here is boiled.
Boiling denatures the proteins present in the cell
membrane and thus, disrupts the cell membrane. For
osmosis, a semi-permeable membrane is required, which
is disrupted in this case. Therefore, osmosis will not
occur. Hence, water does not enter the boiled potato cup.
Get more information on schools.aglasem.com/1757
Who discovered cells and how?
Answer:
Cells were discovered in 1665 by an English Botanist,
Robert Hooke. He used a primitive microscope to observe
cells in a cork slice.
Question 2:
Why is the cell called the structural and functional unit of
life?
Answer:
Cells constitute various components of plants and
animals. A cell is the smallest unit of life and is capable
of all living functions. Cells are the building blocks of life.
This is the reason why cells are referred to as the basic
structural and functional units of life. All cells vary in their
shape, size, and activity they perform. In fact, the
shape and size of the cell is related to the specific
functions they perform.
–
Question 1:
How do substances like CO2 and water move in and out of
the cell? Discuss.
Answer:
The cell membrane is selectively permeable and regulates
themovement of substances in and out of the
cell. Movement of CO2:
CO2 is produced during cellular respiration. Therefore, it is
present in high concentrations inside the cell. This CO2
must be excreted out of the cell. In the cell’s external
environment, the concentration of CO2 is low as
compared to that inside the cell. Therefore, according to
the principle of diffusion, CO2 moves from a region
of higher concentration (inside the cell) towards a region
of lower concentration (outside the cell). Similarly, O2
enters the cell by the process of diffusion when
the concentration of O2 inside the cell is low as
compared to its surroundings.
Movement of water:
Water moves from a region of high concentration to a
region of low concentration through the plasma
membrane. The plasma membrane acts as a semi-
permeable membrane, and this movement of water is
known as osmosis. However, the movement of water
across the plasma membrane of the cell is affected by
the amount of substance dissolved in water.
Question 2:
Why is the plasma membrane called a selectively
permeable membrane?
Answer:
Thecell membraneor the plasma membraneis known as a
selectively permeable membrane because it regulates the
movement of substances in and out of the cell. This
means that the plasma membrane allows the entry of only
some substances and prevents the movement of some
other materials.
–
Question 1:
Fill in the gaps in the following table illustrating
differences between prokaryotic and eukaryotic cells.
–
Question 1:
Can you name the two organelles we have studied that
contain their own genetic material?
Answer:
Mitochondriaandplastids are the two organelles that
contain their own genetic material. Both these organelles
have their own DNA and ribosomes.
Question 2:
If the organisation of a cell is destroyed due to some
physical or chemical influence,
what will happen?
Answer:
Cell is the smallest unit of life, which is capable of all
living functions. If the organisation of a cell is destroyed
due to some physical or chemical influence, then the
ability of the cell to perform all living functions such as
respiration, nutrition, excretion, etc. would be affected.
Question 3:
Why are lysosomes known as suicide bags?
Answer:
Lysosomes are membrane-bound vesicular structures that
contain powerful digestive enzymes. These enzymes are
capable of breaking down any foreign food particle
or microbes entering the cell. Sometimes, lysosomes can
cause self-destruction of a cell by releasing these
digestive enzymes within the cells. Hence, they are also
known as ‘suicidal bags’.
Question 4:
Where are proteins synthesized inside the cell?
Answer:
Ribosomesare the site for protein synthesis. Ribosomes
are very small structures found either in a free state,
suspended in the cytoplasm, or attached to the surface of
the endoplasmic reticulum. They are composed of
ribonucleic acids and proteins.
–
Question 1:
Make a comparison and write down ways in which plant
cells are different from animal cells.
Answer:
Question 2:
How is a prokaryotic cell different from a eukaryotic cell?
Answer:
Question 3:
What would happen if the plasma membrane ruptures or
breaks down?
Answer:
If the plasma membrane of a cell is ruptured, then the cell
will die. The plasma membrane regulates the movement of
substances in and out of the cell by diffusion or osmosis.
Thus, if the plasma membrane is ruptured, then the cell
might leak out its contents.
Question 4:
What would happen to the life of a cell if there was no
Golgi apparatus?
Answer:
If there was no Golgi apparatus in the cell, then most
activities performed by the Golgi apparatus will not take
place.
(i) Membranes of the Golgi apparatus are often connected
to ER membranes. It collects simpler molecules and
combines them to make more complex molecules. These
are then packaged in small vesicles and are either stored
in the cell or sent out as per the requirement. Thus, if the
Golgi apparatus is absent in the cell, then the above
process of storage, modification, and packaging of
products will not be possible.
(ii) The formation of complex sugars from simple sugars
will not be possible as this takes place with the help of
enzymes present in Golgi bodies.
(iii) The Golgi apparatus is involved in the formation of
lysosomes or peroxisomes. Thus, if the Golgi body is
absent in a cell, the synthesis of lysosomes or
peroxisomes will not be possible in the cell.
Question 5:
Which organelle is known as the powerhouse of the cell?
Why?
Answer:
Mitochondriaare known as the powerhouse of cells.
Mitochondria create energy for the cell, and this process
of creating energy for the cell is known as
cellular respiration. Most chemical reactions involved in
cellular respiration occur in the mitochondria. The energy
required for various chemical activities needed for life
is released by the mitochondria in the form of ATP
(Adenosine triphosphate) molecules. For this reason,
mitochondria are known as the powerhouse of cells.
Question 6:
Where do the lipids and proteins constituting the cell
membrane get synthesized?
Answer:
Lipids and proteinsconstituting the cell membrane are
synthesized in the endoplasmic reticulum.
SER (Smooth endoplasmic reticulum) helps in the
manufacturing of lipids.
RER (Rough endoplasmic reticulum) has particles attached
to its surface, called ribosomes. These ribosomes are the
site for protein synthesis.
Question 7:
How does an Amoeba obtain its food?
Answer:
Amoebaobtains its food through the process of
endocytosis. The flexibility of the cell membrane enables
the cell to engulf the solid particles of food and other
materials from its external environment.
Question 8:
What is osmosis?
Answer:
The movement of water molecules from a region of high
concentration to a region of low concentration through a
selectively permeable membrane is called osmosis. It is a
special case of diffusion, where the medium is water.
For example, if the medium surrounding the cell has a
higher water concentration than the cell i.e., if the
solution is a dilute solution, then the cell will gain water
by osmosis.
Movement of water inside the cell
Question 9:
Carry out the following osmosis experiment: Take four
peeled potato halves and scoop 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 the boiled 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.
Answer Discussion
Experimental set up
(i) Water gathers in the hollowed portions of set-up B and
C because water enters the potato as a result of osmosis.
Since the medium surrounding the cell has a higher water
concentration than the cell, the water moves inside by
osmosis. Hence, water gathers in the hollowed portions of
the potato cup.
(ii) Potato A in the experiment acts as a control set-up.
No water gathers in the hollowed portions of potato A.
(iii) Water does not gather in the hollowed portions of
potato A because potato cup A is empty. It is a control
set-up in the experiment. Water is not able to enter potato
D because the potato used here is boiled.
Boiling denatures the proteins present in the cell
membrane and thus, disrupts the cell membrane. For
osmosis, a semi-permeable membrane is required, which
is disrupted in this case. Therefore, osmosis will not
occur. Hence, water does not enter the boiled potato cup.
Get more information on schools.aglasem.com/1757
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