BSEB Bihar Board Class 9 Science Solutions Chapter 5 The Fundamental Unit of Life
Bihar Board Class 9 Science Solutions Chapter 5 The Fundamental Unit of Life Textbook Questions and Answers, Additional Important Questions, Notes.
Bihar Board Class 9 Science Chapter 5 The Fundamental Unit of Life InText Questions and Answers
Who discovered cells, and how?
(i) The cell was discovered by Robert Hook, in 1665.
(ii) He discovered cell in a cork slice with the help of a primitive miscroscope.
Why is the cell called the structural and functional unit of life?
(i) In all living organisms whether as large as elephant or as small as bacteria, it is the cell which consitute the body. Hence, it is called structural unit of life.
(ii) In all living organisms, it is the cell which performs different functions. The cells are the smallest units involved in the division of labour. Hence, it is called the functional unit of life.
How do substances like CO2 and water move in and out of the cell? Discuss.
The substances move from place of higher concentration to the place of lower concentration in a cell. When the concentration of CO2 in the external environment of the cell is higher than that inside the cell, CO2 moves inside the cell. When the concentration ontride the cell becomes low add it is high inside the cell due to metabolic activities, the CO2 moves out. In same way water also moves ontride and inside the cell.
Why is plasma membrane called a selectively permeable menibrane?
Plasma membrane allows some substances to go in and out of the cell, but does not allow some other substances to either enter or leave the cell. That is why, it is called a selectively permeable membrane.
Fill in the gaps in the following table » illustrating differences between prokaryotic ahd eukaryotic cells.
Prokaryotic Cell :
- Size : generally small (1-10 pm) 1 µm = 10-6 m
- Nuclear region : not surrounded by a nuclear membrane and known as nucleoid
- Chromosome: single
- Membrane – bound cell organelles absent
EMkaryotic Cell :
- Size : generally large (5-100 µm)
- Nuclear region : well defined and surrounded by a nuclear membrane
- More than one chromo some
- Membrane-bound cell organelles present
Can you name the two organelles we have studied that contain their o\yn genetic material?
If the organization of a cell is destroyed due to some physical or chemical influence, what ’ will happen?
If the structure of a cell is destroyed, the cell will not be able to perform, its basic functions, such as | respiration, and nutrition, and will not be able to ! synthesise protein. This may stop all the life activities ! of the organism and may result in its death.
Why are lysosomes known as suicide bags?
When the cell is destroyed, the lysosomes explode and their enzymes eat (digest) their own cell. That is why, they are called suicide bags,
Where are proteins synthesized inside the cell.
The proteins are synthesized in the Ribosome i inside the cell.
Bihar Board Class 9 Science Chapter 5 The Fundamental Unit of Life Textbook Questions and Answers
Answer the following questions :
Make a comparison and write down ways in which plant cells are different from animal cells.
We can differentiate between an animal cell and ’ a plant cell and observe the following differences :
Animal cell :
- They do not have cell was .
- They do not have chloroplast.
- They contain small vacuoles.
- They have centro«-some.
- They have cell wall made of cellulose.
- They contain chloroplast.
- They contain large vacuoles.
- They do not have centro some.
How is a prokaryotic cell different from a eukaryotic cell ?
Eukaryotic cell :
- Generally large size (5-100 Hm).
- Nuclear material surrounded by a nuclear membrane.
- More than one chromosome.
- Nucleolus present.
- Membrane-bound cell organelles present.
- Cell division by mitotic or meiotic modes.
Prokaryotic cell :
- Generally small size (1-10 pm).
- Nuclear region (nucle-oid) not surrounded by a nuclear membrane.
- Single chromosome.
- Nucleolus absent.
- Membrane-bound cell organelles absent.
- Cell division by fission or budding (no mitosis).
What would happen if the plasma membrane ruptures or breaks down ?
Plasma membrane is the outer covering of the cell that separates its contents from the surrounding medium. It is a selectively permeable membrane. If it ruptures or breaks down the cytoplasm will come in direct contact with the surrounding medium and the act of selection will stop.
What would happen to the life of a cell if there was no Golgi apparatus ?
If the cell does not have golgi apparatus, the materials synthesized in the endoplasmic reticulum will not be carried to intracellular and extracellular targets. Lysosomes also will not be formed and, as a result, several enzymes and hormones will not be formed that are responsible for excretion of waste matter. All this will cause the cell’s life to be reduced.
Which organelle is known as the powerhouse of the cell ? Why ?
Mitochondria are called the powerhouse of ther cell. They produce energy, which is stored in the form of ATP molecules. This energy is used in several life processes. That is why, mitochondria are called powerhouse.
Where do the lipids and proteins constituting the cell membrane get synthesized ?
The lipids and proteins constituting the cell membrane are synthesized in the endoplasmic reticulum.
How does an Amoeba obtain its food ?
Amoeba is a unicellular organism. Its cell has several vacuoles. One of these is the food vacuole. The food vacuole is full of food, and from here amoeba gets its food.
What is osmosis?
The movement of water molecules through a selectively permeable membrane from an area of higher concentration to an area of lower concentration is called osmosis. The movement of water depends on the substances dissolved in it.
Carry out the following osmosis experiment: Take four peeled potatoes halves and scoos each one out to make potato cups. One of these potato cups should be made from aboiled potato. Put each potato cup in a troogh 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 boiled potato cup D.
Keep these four hours. Then observe the four potato cups and answer the following :
(а) Explain why water gathers in the hollowed portion of B and C.
(b) Why is potato A necessary for this experiment?
(c) Explain why water does not gather in the” hollo wed out portion of A and D.
(a) A potato is made up of several cells. The cell membrane of the cells is selectively permeable. Cups B and C are filled with sugar and salt respectively, while ‘ their outer part is in contact with water. Therefore, the concentration of water is higher outside the potato as compared to the inside of potato. Thus, due to osmosis, water moves towards the inside of potato .from its outside. As a result, water collects inside cups B and C.
(b) Cup A is important in this experiment because it shows that if two solutions with the same concentration are taken, then there is no movement in the water molecules.
(c) Water does not gather inside cups A and D because cup D is made of boiled potato. Its cells are dead and their cell membranes are no more selectively permeable. Therefore, no osmosis takes place and water does not go inside the potato from outside. Potato cup A has been left empty. Therefore, the concentration on both sides of the cell membrane is equal. As a result, there is no movement in the water, molecules. Thus, water does not collect inside cups A and D. V
Bihar Board Class 9 Science Chapter 5 The Fundamental Unit of Life Additional Important Questions and Answers
Very Short Answer Type Questions
Who coined the word ‘cell’?
Robert Hooke (1665).
Which instrument helps you to look at the cellular structure of an onion peel?
Draw a labelled diagram of a compound microscope.
Draw the diagram of an onion peel as shown by the compound microscope.
Will there be a difference in the temporary slides of the peels of a big and a small Onion as seen under the microscope?
No, the cellular structure’ of/both the peels will be the same.
Short Answer Type Questions
What is plasma membrane?
The outer covering of a cell that separates its contents from the surrounding medium is called the plasma membrane.
What is the main feature of the plasma membrane? .
Plasma membrane is selectively permeable as it allows only some substances from the surrounding medium to enter into or go out of the cell wThile stops the movement (entry and exit) of some other substances.
What is osmosis?
The movement of water molecules through a selectively permeable membrane from an area of higher concentration to an area of lower concentration is called Osmosis.
What will happen if you place a plant or an animal cell in sugar or salt solution?
One out of the three conditions given below’will happen:
(i) If the sugar or salt solution is highly concentrated, then water will go inside the cell through osmosis.
(ii) If the concentration of cytoplasm and sugar or salt solution is equal, then water will go inside the cell.
(iii) If the sugar or salt solution is less concentrated, then water will go from the cell into the solution.
What will happen if the plasma membrane tears down or breaks away? Discuss in class and write down in your copy. ,
If the plasma membrane tears down or breaks – away, the cytoplasm will come in direct contact with the surrounding medium. The substances which are denied entry into the cell by the plasma membrane will now easily enter the cell and may prove harmful for it. The balance of water exchange will also be destroyed. This may eventually lead to the death of the cell. ;
Why is plasma membrane called a selectively permeable membrane?
Plasma membrane allows some substances to go in and out of the cell, biiit does not allow some other substances to either enter or leave the cell. That is why, it is called a selectively permeable membrane.