Class8 Cell and Cell Organelles exercise question answer 8th general science
Class 8 science chapter 10 question answer Maharashtra board Science digest std 8 maharashtra board Class 8 science chapter 10
1. Who am I ?
a. I am ATP producing factory.
Ans:
Mitochondria
b. I am single layered, but maintain cellular osmotic pressure.
Ans:
Vcuole
c. I support the cell, but I am not cell wall. I have a body resembling net.
Ans:
Endoplasmic reticulum
d. I am chemical factory of the cell.
Ans:
chloroplasts in case of plant cells can be called chemical factory as they
synthesise carbohydrates. Ribosomes also synthesis proteins, so those can also
be called chemical factory. Golgi complex is secretory in function, hence it
can be also called factory.
e. Leaves are green because of me.
Ans:
chloroplasts
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2. What would have happened ? If…….
a. RBCs had mitochondria.
Ans:
Mitochondria continuously carry out oxidation and form energy inside the cell.
They produce energy rich compound, ATP. In this process, they utilize
carbohydrates, fats and proteins present in the cell. If RBCs has mitochondria,
they would have used oxygen for this purpose than carrying it to all the cells
of the body. The cells would not have obtained oxygen.
b. There had been no difference between mitochondria and plastids.
Ans:
Mitochondria carry out oxidation of
carbohydrates, fats, etc. with the help of enzymes. Plastids are synthesising carbohydrates with the help
of solar energy and chlorophyll. Both the cell organelle have their own sets of
different enzymes as per their own sets of different enzymes as per their role.
If there would have been no difference between mitochondria and plastids, the
specific functions would not have been taken place.
c. Genes had been absent on the chromosomes.
Ans:
Genes are functional segments on the
chromosomes which are responsible for transmitting the hereditary information.
The protein synthesis process also is initiated due to genes. If genes were
absent, these processes will be ended.
d. Plasma membrane had not been selectively permeable.
Ans:
Selectively permeable membrane allows some substances to enter the cell, while prevents other unwanted or harmful substances. If plasma membrane would not have been selectively permeable, there would be no control over entry and exit of any substances. The process of osmosis would also be erroneous in such case.
e. Plants lacked anthocyanin.
Ans:
If plant laced anthocyanin, no part of the plant would display purple or blue colour. Anthocyanin attracts the insects for pollination and seed dispersal. These process will be affected due to lack of anthocyanin. These pigments are also said to be protective in nature for the plant. This protection will not be given to the plant in absence of anthocyanin.
3. Who is odd man among us? Give reason.
a. Nucleolus, mitochondria, plastids, endoplasmic reticulum
Ans:
Nucleolus ( All the others are cell organelles but nucleolus is not a cell
organelle present in cytoplasm.)
General science question answer for 8th class 8th class science all question answer Class 8 general science chapter 9 question answer Class 8 question answer Cell and Cell Organelles Cell and Cell Organelles class 8 question answer maharshtra board
b. DNA, Ribosomes, Chlorophyll
Ans:
Chlorophyll ( DNA and Ribosomes are
present in plant as well as in animal
cells. Chlorophyll is present only in plant cells.)
4. Give functions.
a. Plasma membrane
Ans:
Plasma membrane acts as a selectively permeable membrane. It allows entry of those useful substances which are needed for the cell. It does not allow entry of the harmful and unwanted substances.
2.Plasma membrane keeps the homeostasis in the cell. The cell is kept in steady state even if the external environment changes.
3.Plasma membrane is responsible for processes of endocytosis and exocytosis.
4.The processes of diffusion and osmosis are possible only due to plasma membrane.
5.In
animal cells, plasma membrane is the outermost protective covering of the cell.
b. Cytoplasm
Ans:
- All the cell organelles are spread in the cytoplasm of a cell.
- The cytoplasm is the medium for many cellular chemical reactions.
- The cytosol which is the part of cytoplasm other than cell organelles stores many vital substances like amino acids, glucose, vitamins, etc.
- Cytosol also helps in the cellular movements.
c. Lysosome
Ans:
- Lysosome helps in the destruction of attacking viruses and bacteria and therby help in the immune response.
- Lysosomes act as demolition squads. They destroy worn out cellular organelles and organelles and organic debris. This process is called autolysis which means self-destruction.
- They are also called suicide bags as in a worn out, damaged or old cell, lysosomes automatically burst. The lytic enzymes present in the lysosome digest their own cells.
d. Vacuole
Ans:
- Vacuole maintain the osmotic pressure of the cell.
- Various metabolic by products and end products such as glycogen, proteins, water, etc. are stored in the lysosome.
- In food vacuole of amoeba, the food is temporarily stored till digestion . in other animal cells, vacuole can store waste product and food.
- Vacuole of plant cells can provide turgidity and rigidity as it contains good amount of cell sap
e. Nucleus
Ans:
- Nucleus is the controlling centre for the entire cell.
- It controls all metabolic activities of the cell.
- The cell division is possible due to the nucleus.
- The chromosomes present in the nucleus carry the genes. These genes are responsible for the transmission of hereditary characters form parental generation to the next generations.
5. Who gives me the colour? (Select the correct option).
|
a. Red tomato |
1. Chlorophyll |
|
b. Green leaf |
2. Carotene |
|
c. Carrot
|
3. Anthocyanin |
|
d. Violet |
4. Carotene |
Ans:
a. Red
tomato – 2. Lycopene
b.
Green leaf – 1. Chlorophyll
c.
Carrot –
4. Carotene
d.
Violet –
3. Anthocyanin
