CHAPTER NO 5
FUNDAMENTAL UNIT OF LIFE
DATE 07/MAY/2016
EXERCISE
Q 1- Make a comparison and write down ways in which plant cells are different from animal cells.
ANS-
PLANT CELLS ANIMAL CELL
(i) Cell wall is present. (i) Cell wall is absent.
(ii) Plastids are present. (ii) Plastids are absent.
(iii) Vacuoles is single and occupy (iii) Vacuoles are many and small.
the maximum part of the cell
(Vacuoles is large).
Q 2- How is a prokaryotic cell different from a eukaryotic cell?
ANS-
PROKARYOTIC CELLS EUKARYOTIC CELLS
(i) Primitive nucleus not bounded by (i) The nuclear bounded by
nuclear membrane and known as nuclead. nuclear membrane.
(ii) Size of the cell is small. (ii) Size is large.
(iii) Membrane bound organelles absent. (iii) Membrane bound
organelles present.
Q 3- What would happen if the plasma membrane ruptures or breaks down?
ANS- If the plasma membrane breaks down or ruptures the cell will die. Plasma membrane helps of in and out of the substances from the cell, if it break down then the cell contents might leak out.
Q 4- What would happen to the life of a cell if there was no Golgi apparatus?
ANS- Golgi Apparatus helps in storing food for cell. If it is absent then the packaging, storing process will be absent.
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.
Q 5- Which organelle is known as the powerhouse of the cell? Why?
ANS- Mitochondria are 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.
Q 6- Where do the lipids and proteins constituting the cell membrane get synthesised?
ANS- 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.
Q 7- How does an Amoeba obtain its food?
ANS- Amoeba obtains its food through the process of endocytosis. The fexibility of the cell membrane enables the cell to engulf the solid particles of food and other materials from its external environment.
Q 8- What is osmosis?
ANS- 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.
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 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.
ANS- (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.
Q 3- What would happen if the plasma membrane ruptures or breaks down?
ANS- If the plasma membrane breaks down or ruptures the cell will die. Plasma membrane helps of in and out of the substances from the cell, if it break down then the cell contents might leak out.
Q 4- What would happen to the life of a cell if there was no Golgi apparatus?
ANS- Golgi Apparatus helps in storing food for cell. If it is absent then the packaging, storing process will be absent.
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.
Q 5- Which organelle is known as the powerhouse of the cell? Why?
ANS- Mitochondria are 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.
Q 6- Where do the lipids and proteins constituting the cell membrane get synthesised?
ANS- 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.
Q 7- How does an Amoeba obtain its food?
ANS- Amoeba obtains its food through the process of endocytosis. The fexibility of the cell membrane enables the cell to engulf the solid particles of food and other materials from its external environment.
Q 8- What is osmosis?
ANS- 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.
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 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.
ANS- (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.
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