Q.What would have happened? If……….
Question a. RBCs had mitochondria.
Answer:
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.
Question b. There had been no difference between mitochondria and plastids.
Answer:
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 organelles have 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.
Question c. Genes had been absent on the chromosomes.
Answer:
Genes are functional segments on the chromosomes which are responsible for transmitting the hereditary information.
Question d. Plasma membrane had not been selectively permeable.
Answer:
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.
Question e.Plants lacked anthocyanin.
Answer:
If plants lacked anthocyanin, no part of the plant would display purple or blue colour. Anthocyanin attracts the insects for pollination and seed dispersal. These processes 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.
Vacuoles -
Answer -
1. Vacuoles maintain the osmotic pressure of the cell.
2. Various metabolic byproducts and end products such as glycogen,
proteins, water, etc. are stored in the lysosome.
3. In food vacuole of amoeba, the food is temporarily stored till digestion.
In other animal cells, vacuoles can store waste products and food.
4. Vacuoles of plant cells can provide turgidity and rigidity as it contains
good amount of cell sap.
Answer -
1. Lysosome helps in the destruction of attacking viruses and bacteria and
thereby help in the immune response.
2. Lysosomes act as demolition squads. They destroy worn-out cellular
organelles and organic debris. This process is called autolysis which All
Pages Means self-destruction.
3. They are also called suicide bags as in a worn out, damaged or old cell,
3. 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.
4. Lysosomes can digest stored proteins, fats during starvation.
Q.1) Cell wall is mainly composed of carbohydrates like ……….. and
…………. .
Answer:
Cell wall is mainly composed of carbohydrates like cellulose and pectin.
Q.2) Plasma membrane is said to be a ……………. …………….. membrane
as it allows some substances to enter the cell, while prevents other
substances.
Answer:
Plasma membrane is said to be a selectively permeable membrane as it allows some substances to enter the cell, while prevents other substances.
Q.3) Homeostasis is maintained in the cell by ………….. .
Answer:
Homeostasis is maintained in the cell by plasma membrane.
Q.4) An …………… is a specialized subunit having specific function within
the cell.
Answer:
An organelle is a specialized subunit having specific function within the cell.
Q.6) ……………. has ribosome granules on its outer surface.
Answer:
Rough ER has ribosome granules on its outer surface.
Answer the following questions in one sentence:
Question 1. What are the components of plasma membrane?
Answer:
In plasma membrane, protein molecules are embedded in two layers of
phospholipids.
Question 2. Which part of the cell maintains the homeostasis?
Answer:
Plasma membrane of the cell maintains the homeostasis.
Question 3. What are genes?
Answer:
Genes are the functional segments on the chromosomes that carry hereditary information from the parental generation to the offspring.
Question 4. What is meant by rough ER?
Answer:
The endoplasmic reticulum that has ribosomes on its outer membrane is
called rough ER.
Question 5. Write the examples of plant pigments.
Answer:
Chlorophyll, Carotene, Xanthophyll, Anthocyanin, Betalains and Lycopene are some of the plant pigments.
Question 6. What are the inclusions in the stroma of chloroplasts?
Answer:
Enzymes, DNA, ribosomes and carbohydrates that are necessary for
photosynthesis are present in the stroma of the chloroplasts.
Question 7. Which staining technique was developed by Camilio Golgi? Where was this technique used?
Answer:
Camilio Golgi developed the staining technique called ‘Black reaction’ which was used in the study of nervous system.
Question 8. What type of work is done by National Centre for Cell Science?
Answer:
National Centre for Cell Science – NCCS is involved in research in cytology and research about cancer treatment and it also provides services for National Animal cell repository.
Question 9. Ripe tomatoes appear red.
Answer:
When green tomatoes become ripe they lose chlorophyll and develop red pigment in them called lycopene. Therefore, ripe tomatoes appear red.
Give scientific reasons:
Question 1.
Raisins swell after keeping in plain water.
Answer:
When raisins are placed in plain water, there is action of endosmosis. The outer skin of raisins acts like selectively permeable membrane. Since the concentration of water inside the raisin is lesser than the concentration of water in the outer medium, water enters in the raisin. This causes raisins to swell after keeping them in plain water.
Question 2.
The fruit pieces kept in sugar syrup show shrinking.
Answer:
There is more concentration of water in the fruit pieces as compared to the concentration of water in the sugar syrup. Therefore, water is lost out by exosmosis. The membranes of the fruit pieces act as selectively permeable membranes. Thus the process of plasmolysis occurs resulting into shrinking of the fruit pieces.
Question 3.
The nucleus of the sieve tubes of the plant phloem is lost.
Answer:
The sieve tubes of the plant phloem conduct the food in plants. To make this transport easier, the nucleus of the sieve tubes of the plant phloem is lost.
Question 4.
Plant cells have less mitochondria than those of animal cells.
Answer:
Mitochondria are the cell organelles which are called powerhouse of the cell.They produce energy in the form of ATP. Animals are motile and need more energy for walking, running and moving. Plants are stationary. They do not need energy to greater extent. Therefore, they have lesser number of mitochondria.
Question 5.
Vacuoles do not have any typical size or shape.
Answer:
Vacuoles change their shape and size as per the need of the cell. Thus they do not have any fixed shape or size.
Give function
1) Plastids Answer:
Ans -
1. Chloroplasts contain chlorophyll. They carry out the process of
photosynthesis. They convert solar energy to chemical energy in the
form of food.
2. Chromoplasts with different pigments can impart different colours to
flowers and fruits.
3. Leucoplasts are responsible for the synthesis and storage of food like
starch, oils and proteins.
2) Golgi complex:
Ans -
8. Different secretions are prepared in the Golgi complex. Hence it is called the secretory organ of the cell.
9. The secretions are modified and sorted out as per their functions. Theyare further packed.
10. The enzymes, mucus, proteins, pigments, etc. are sorted and then
dispatched to various target regions like plasma membrane, lysosome,
etc.
11. Golgi complex also produces vacuoles and secretory vesicles.
12. Formation of cell wall, plasma membrane and lysosomes is aided by
Golgi complex.
Answer the following questions:
Question 1.
How does endosmosis and exosmosis occur in the cell?
Answer:
1. When the water concentration inside the cell is less as compared to the medium in which it is present, then the endosmosis takes place. This
makes the water to enter inside the cell.
2. When water concentration inside the cell is more than the water
concentration in the medium in which it is present, then the water
comes out of the cell. This is called exosmosis.
3. Since the cell membrane acts as a semipermeable membrane, the
processes of endosmosis and exosmosis takes place in the cell.
Question 2.
What is cytoplasm? What are the constituents of cytoplasm?
Answer:
1. The jelly like material present between the cell membrane and nucleus is called cytoplasm.
2. Cytoplasm without cell organelles is called cytosol.
3. All the cell organelles are spread in the cytoplasm.
4. Cytosol stores many vital constituents such as amino acids, glucose,
vitamins, etc.
5. The cytoplasm of animal cells is dense and granular while that of plant cells is thin and peripheral. It is pushed to sides due to large central vacuole.
Question 3.
Describe the structure of the nucleus in the cell.
Answer:
1. Nucleus is the most important part of the eukaryotic cell.
2. Inside the nucleus there is round darkly stained nucleolus.
3. The nucleus is covered over by double membrane which is porous.
4. The nuclear pores allow the transport of different substances in and out of the nucleus to cytoplasm.
5. Inside the nucleus is the chromatin network which contains
chromosomes. Chromatin fibres are thin which condense to form
chromosomes. The chromosomes become clear and distinct at the time
of cell division.
6. In every cell there are specific number of chromosomes. Chromosomes contain genes which are bearers of hereditary characters.
Question 4.
Why is endoplasmic reticulum compared with the pipelines?
Answer:
1. The endoplasmic reticulum works as pipelines to carry different
substances in the cell.
2. It is a net like structure consisting of interconnected small tubes and
sheets filled with fluid.
3. On the inner side the E.R. is connected to nucleus while at the outer side
it is in contact with plasma membrane. Therefore, it works like a
pipeline.
Question 5.
Write an account of the different structures seen in Golgi complex.
Answer:
1. Golgi complex is made up of 5-8 hollow and flat sacs called cisternae.
2. These are placed parallel to each other and are filled with different
enzymes.
3. Golgi complex has two faces called forming face and maturation face.
4. The proteins packed in vesicles and coming from ER reach Golgi
complex through cytoplasm.
5. They fuse with the formation face of the Golgi membranes for emptying their contents in the cisternae.
6. When these contents pass through the cisternae, they are chemically
modified with the help of enzymes and are again packed in the vesicles.
7. These vesicles come out of Golgi ‘ complex at the maturation face.
Question 6.
How is energy produced in the mitochondria? How the structures
of mitochondria help in this process?
Answer:
1. Around every mitochondrion there is a double membrane.
2. The outer membrane of these is porous while the inner membrane is
deeply folded.
3. These folds or ‘cristae’ enclose the matrix filled with proteinaceous gel
containing ribosomes, phosphate granules and DNA. Protein synthesis
takes place in this matrix.
4. Mitochondria carry out oxidation of carbohydrates and fats in the cell.
This produces energy in the form of ATP, s i.e. Adenosine Tri Phosphate.
Question 7.
What is the benefit of foldings of inner membrane in
mitochondria?
Answer :
The structure of the inner mitochondrial membrane is extensively folded and compartmentalized. The numerous imaginations of the membrane are called cristae. This folded inner membrane increases the area which is about 5 times more than that the outer membrane due to cristae. Cristae membranes have small round protein complexes known as Fx particles. In these particles the process of energy production goes on.
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