Exams Prep Master
A cell is defined as the functional and structural unit of life. Every cell is surrounded by a cell membrane that bifurcates the external and internal environments of the cell. The cytoplasm is known as the interior environment of a cell. It contains cellular machinery and structural elements. In the center of the cell, the nucleus is present which includes all the hereditary information of an organism. Some of the molecules present in the cell are carbohydrates, starch, protein, and sugar. Here, in this article, we have curtailed important questions for Class 11 Biology Chapter 8 Cell.
Very Short Answer Question [1 Mark]
Ques. What is the definition of mesosome?
Ans. Mesosomes are developed by the extension of the plasma membrane into the cell in prokaryotes. It results in the formation of the cell wall, DNA replication, and disturbs DNA to daughter cells.
Ques. Why are mitochondria called the powerhouse of the cell?
Ans. The reason why mitochondria are called the powerhouse of the cell is that it carries out the process of anaerobic respiration. Further, mitochondria generate ATP for the functioning of the cell.
Ques. What is ATP?
Ans. ATP is Adenosine triphosphate is an organic molecule. They provide energy to various biochemical processes in the body. ATP is known as the energy currency of the cell.
Ques. What is the definition of histones? What role do they play?
Ans. Histones are alkaline proteins present inside the nucleus of eukaryotic cells. They are the key proteins in chromatin. The role of histones is to package the DNA into structural units known as nucleosomes.
Ques. What is a satellite chromosome?
Ans. Satellite chromosomes are the chromosomes with additional or secondary constriction at the distal part of the arm which is formed by chromatin thread. The chromosomes 13, 14, 15, 16, 21, and 22 are satellite chromosomes. Satellite chromosomes are also known as marker chromosomes. These are also known as marker chromosomes.
Ques. Which cell organelle is only found in animal cells?
Ans. Centrosomes is the cell organelle that is only present in animal cells.
Ques. What are the different types of cells?
Ans. Cells are differentiated on the basis of their structure, composition, functions etc. The two main types of cells are Prokaryotes and Eukaryotes. The difference between them is the nucleus. Eukaryotic cells have nucleus and prokaryotic cells do not have nucleus.
Ques. Define histones? What is the role of histones?
Ans. Histones are alkaline proteins present in the nucleus of eukaryotic cells. The role of the histones is to pack the DNA into structural units known as nucleosomes. Histones are the most significant proteins in chromatin.
Ques. What are the different types of plastids present in a plant cell?
Ans. A plant cell has three types of plastids -leucoplast, chloroplast and chromoplast.
Ques. Who discovered the cell?
Ans. In the year 1665, English natural philosopher Robert Hooke was the first person to discover the cell. Later on, Antonie Van Leeuwenhoek, a Dutch scientist studied cells under another microscope.
Short Answer Question [2 Marks]
Ques. What does “S” depicts in the 70S and 80S ribosome?
Ans. “S” is Svedberg’s unit for sedimentation coefficient. In the 70S and 80S ribosome, it stands for the rate of sedimentation of cells while ultracentrifugation. The more the structure of the cell is heavy the more will be the sedimentation coefficient.
Ques. What is the biochemical composition of the plasma membrane?
Ans. The plasma membrane consists of different biochemical components that are mentioned below:
- Lipids- 20-79%
- Proteins- 20-70%
- Carbohydrates- 1-5%
- Water- 20%
Ques. Why is vacuole important in a plant cell?
Ans. In a plant cell, a vacuole is a membrane-bound space in the cytoplasm. It occupies 90% of the cell during osmosis. Vacuole consists of sap, excretory products, water and other materials that are not useful for the cell. Further, vacuole helps in maintaining the turgor pressure against the cell wall. Thus, it allows the cell to maintain its shape and fluid balance.
Ques. Why is the cell known as the basic unit of life?
Ans. There are trillions of cells present in the human body. Various organisms are there with single cells such as amoeba. New cells are formed by the division of old cells. Cells consist of organelles that carry out various life functions. Cells in the human body carry the same genetic material that conveys all the hereditary information of an individual. This is the main reason cells are called the basic unit of life.
Ques. What is the key role of the chloroplast in a plant cell?
Ans. Chloroplast is a green color plastid that consists of green-colored pigments called chlorophyll. It is present inside the plant cell. The key role of the chloroplast is it allows the production of food via photosynthesis.
Long Answer Question [3 marks]
Ques. Name functions of Plant cells.
Ans. Some of the integral functions of the plant cell are:
- Plant cells are known as the building blocks of plants.
- Cell walls provide shape to the plant cell and protect the inner cell organelles.
- Plant cells stored food in the form of energy.
- Plant cells play a major role in biological processes such as transpiration, photosynthesis, etc.
- Plant cells act as a pathway that transports water and nutrients from the roots and leaves to different parts of the plants.
Ques. Write down the different characteristics of prokaryotic cells?
Ans. Prokaryotic cell characteristics are as follows:
- A prokaryotic cell is encircled by a cell membrane.
- A prokaryotic cell does not have chloroplast, nucleus and mitochondria.
- The DNA of prokaryotic cells is circular and it is not correlated with basic proteins.
- In Prokaryotic cells cytoplasm is filled with dense granules, maximum are ribosomes.
- Thylakoids are scattered in the chloroplast in prokaryotic cells. And they are also not placed in the form of stacks.
Ques. What are the different functions of cells?
Ans. Cells are the basic unit of life. They perform numerous integral functions that are necessary for the development and growth of an organism. A few of the functions of cells are:
- Cells play a key role in the process of reproduction.
- Another major function of cells is that they allow the growth of cell division.
- Cells form the structure of the body and also provide support to it.
- Transportation of substances is made possible because of cells only.
- Cells provide energy to the body.
Ques. Explain in brief about cell theory?
Ans. The cell theory is based on the below-mentioned assumption:
- The basic structural and functional unit of life is the cell.
- All living organisms are made up of cells.
- All cells are developed from pre-existing cells.
Very Long Answer Question [5 marks]
Ques. Differentiate between Smooth Endoplasmic Reticulum and Rough Endoplasmic Reticulum.
Ans. The difference between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER) are as follows:
| Rough Endoplasmic Reticulum (RER) | Smooth Endoplasmic Reticulum (SER) |
|---|---|
| Ribosomes are attached to their surface. | Ribosomes are not attached to their surface. |
| RER is made up of tubules and cisternae. | SER is made up of vesicles and tubules. |
| Rough Endoplasmic Reticulum takes part in the protein and enzyme synthesis process. | Smooth Endoplasmic Reticulum participates in the synthesis of lipids, glycogen and steroids. |
| RER can be developed from the nuclear envelope. | SER might be developed from RER. |
| Rough Endoplasmic Reticulum is present inside the cell. | Smooth Endoplasmic Reticulum is situated near the cell periphery. |
| It is connected to the nuclear envelope. | It is connected to the plasmalemma. |
| RER does not have detoxification enzymes. | SER consists of detoxification enzymes. |
| Gives rise to lysosomes. | Gives rise to sphaerosomes. |
Ques. Explain cell theory in brief?
Ans. Two scientists Theodor Schleiden and Matthias Schwann proposed the cell theory in 1839. According to their theory:
- The new cell is formed by the already existing cell.
- The chemical structure of all cells is identical.
- The cell is the structural and functional unit of all living things.
- From a parent cell to a child cell hereditary information is passed.
- The fundamental biochemical reactions of life take place within cells.
- All living organisms present on the earth consist of one or more cells.
Ques. Differentiate between plant cells and animal cells?
Ans. The difference between animal cells and plant cells is as follows:
| Plant Cell | Animal Cell |
|---|---|
| Plant cells are rectangular in Shape. | Animal cells are round or irregular in shape. |
| In a plant cell, a cell wall is present. | No cell wall is present in the animal cell. |
| Plant cell does not contain centrosomes. | Centrosomes are present in the animal cell. |
| Plant cells have Plastids. | Animal cells do not have Plastids. |
| In plant cells vacuoles are large and few. | Vacuoles are small and present in large quantities in animal cells. |
| The number of mitochondria is few. | Large number of mitochondria are there. |
| Mode of nutrition is autotrophic. | Mode of nutrition is Heterotrophic. |
| In a plant cell, the nucleus is present on one side of the cell. | In an animal cell, the nucleus is found in the center of the cell. |
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