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Question (1):
Why were the scientists not able to observe most of the cell organelles before 1940?
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Answer:
Before 1940, scientists could view the cell only under a light microscope. The invention of the electron microscope in 1940 enabled the scientists to observe the cell in greater detail.
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Question (2):
What is the function of the cell wall?
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Answer:
The cell wall lies outside the plasma membrane and is responsible for providing structural strengths to the plants.
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Question (3):
Why are lysosomes called digestive bags or suicide bags?
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Answer:
 They serve as intracellular digestive system
 They destroy any foreign material inside the cell
 They also remove the worn out and poorly working cell organelles by digesting them to make way for a replacement
 They may even digest away the entire damaged or dead cell containing them
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Question (4):
Why are peroxisomes mostly found in kidney and liver cells?
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Answer:
Peroxisomes contain powerful oxidative enzymes, which specialize in carrying out certain oxidative reactions, in order to remove toxic substances.
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Question (5):
Why are mitochondria also called 'The Power House of cell'?
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Answer:
Energy in the food molecules is converted here (in the mitochondria) into usable energy and stored as ATP molecules. Hence, they are called the power house of the cells.
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Question (6):
There would be no plant life if chloroplasts did not exist. Justify.
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Answer:
Chloroplasts contain the pigment chlorophyll which is responsible for food preparation by photosynthesis. Hence, if there were no chloroplasts then there would not have been plant life.
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Question (7):
Why is the golgi apparatus called the secretory organelle of the cell?
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Answer:
This is because it packages material synthesized in the ER and dispatches it to intracellular and (plasma membrane and lysosomes) extracellular targets.
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Question (8):
Why is variation not possible in mitotic division of cells?
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Answer:
In mitosis, the cell divides into two (each having the same number of cells as the mother cell) giving rise to two identical daughter cells. Hence, variation is not possible.
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Question (9):
The daughter cell of meiotic division is different from the parent cells. Explain.
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Answer:
In meiosis, exchange of genes takes place between the two germ cells and hence, the daughter cell will differ from the parent cells.
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Question (10):
Differentiate between smooth and rough endoplasmic reticulum.
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Answer:
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Question (11):
Give the importance of cristae in mitochondria.
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Answer:
The finger-like cristae present in the inner-folded membrane greatly increase the surface area of the membrane.
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Question (12):
Give one similarity and one dissimilarity between plastids and mitochondria.
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Answer:
 Similarity: Their structures are more or less the same.
 Dissimilarity: Mitochondria have cristae which are absent in plastids.
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Question (13):
In many plant cells the nucleus and other cell organelles are pushed near the boundary walls. Explain.
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Answer:
In plant cells, a single prominent vacuole occupies 90% of the volume of a cell and hence, all the organelles are pushed to the side of the cell.
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Question (14):
Differentiate between the cell of an elephant and a plant cell (2 differences).
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Answer:
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Question (15):
During cell division, the number of chromosomes in a cell becomes half of what it was initially. What type of cell is it? Name the type of cell divison.
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Answer:
It is a germ cell.
The type of cell division is meiosis.
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Question (16):
Why does not a child exactly resemble his father or mother?
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Answer:
A child does not exactly resemble his father or mother because the sperm and egg cells undergo meiotic division which leads to variation.
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Question (17):
Identify the diagrams given below. To which stage of mitosis do they belong? Given reasons.
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Answer:
a) Metaphase, because the chromosomes have arranged themselves in the equatorial plate.
b) Anaphase, because the sets of daughter chromosomes are being pulled to the opposite poles.
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Question (18):
In which phase of cell division do the following occur:
a) Disappearance of nuclear envelope
b) Development of spindle
c) Reappearance of nuclear membrane
d) Reorganization of nucleus at the poles of the dividing cells
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Answer:
a) Disappearance of nuclear envelope: Prophase
b) Development of spindle: Metaphase
c) Reappearance of nuclear membrane: Telophase
d) Reorganization of nucleus at the poles of the dividing cells: Anaphase
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Question (19):
Give two characteristics unique to meiotic divison.
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Answer:
Two characteristics unique to meiotic divison are:
 It takes place only in germ cells
 Crossing over takes place
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Question (20):
Identify the odd one out: nucleus, plastid, mitochondria, peroxisomes.
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Answer:
Plastid is the odd one out. It is the only organelle out of the above not present in animal cells.
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Question (21):
What is a cell?
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Answer:
A cell is the structural and functional unit of living organisms.
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Question (22):
What are the chief components of the nucleus?
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Answer:
The chief components of the nucleus are:
 Chromatin
 Nucleolus
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Question (23):
Name two components that the cell membrane encloses.
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Answer:
The two components that the cell membrane encloses are:
 Nucleus
 Cytoplasm
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Question (24):
What are the two types of endoplasmic reticulum (ER)?
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Answer:
The two types of endoplasmic reticulum are:
 Rough ER
 Smooth ER
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Question (25):
Which organelle is most vital for the survival of a cell?
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Answer:
Nucleus is most vital for the survival of a cell.
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Question (26):
Define the endoplasmic reticulum.
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Answer:
It is a membrane network enclosing a fluid filled lumen which almost fills up the intracellular cavity.
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Question (27):
Define golgi apparatus.
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Answer:
Golgi apparatus consists of a set of membrane bound, fluid filled vesicles, vacuoles and flattened closed sacs called cisternae which are placed one on top of the other in parallel rows.
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Question (28):
Who discovered cells?
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Answer:
Robert Hooke discovered cells.
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Question (29):
What is the cell theory? Who proposed it? When?
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Answer:
All plants and animals are composed of cells and that the cell is the basic unit of life. Cell theory was proposed by M.Schleiden in 1838 and T.Schwan in 1839.
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Question (30):
What are lysosomes?
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Answer:
Lysosomes are simple, tiny spherical sac-like structures evenly distributed in the cytoplasm.
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Question (31):
What are peroxisomes?
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Answer:
They are small spherical organelles containing powerful oxidative enzymes. They are bound by a single membrane and are mostly found in kidney and liver cells.
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Question (32):
Name the important function of peroxisomes.
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Answer:
Important function of peroxisomes is detoxification or removal of toxic substances.
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Question (33):
What is the difference between vacuoles of plant and animal cells?
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Answer:
In plant cells they are large and permanent and in animal cells they are small and temporary.
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Question (34):
Which cell organelle is responsible for release of energy as ATP?
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Answer:
Mitochondria is responsible for release of energy as ATP.
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Question (35):
Name the four phases of mitosis.
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Answer:
The four phases of mitosis are:
 Prophase
 Metaphase
 Anaphase
 Telophase
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Question (36):
How many daughter cells are produced in the case of meiosis?
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Answer:
Four daughter cells are produced in the case of meiosis.
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Question (37):
When and how is the cell plate formed?
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Answer:
A cell plate is formed during telophase of mitosis when two cells are separated.
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Question (38):
In meiosis, why is a reduction in number of chromosomes necessary in the germ cell?
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Answer:
If the gametes are diploid (2n), then on fertilization the zygote will contain twice the number of diploid chromosomes (4n). To avoid this, germ cells undergo reduction division.
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Question (39):
Give two properties that are unique to meiosis.
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Answer:
The two properties that are uniques to meiosis are:
 Chromosome number in gametes becomes half
 Exchange of genes results in variation
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Question (40):
Give two differences between Meiosis and Mitosis.
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Answer:
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