Ch. 5 The Fundamental Unit of Life
Q. How does a living cell perform all the basic function?
A. Lysosomes are the waste disposal organelles of the cell containing digestive enzymes. During the disturbance in the cell metabolism lysosomes burst and the enzymes thus released digest their own cell.
Q. How materials are transported across cell membrane?
A. 1. Gases like CO2 (cellular waste and is to be excreted by the cell) accumulate in high concentration inside the cell. A soon as there is difference in concentration of CO2 inside and outside the cell i.e. low concentration outside, CO2 moves out of the cell by diffusion.
2. Similarly O2 enters the cell by diffusion when concentration of O2 inside the cell decreases.
3. The movement of water across the plasma membrane is affected by the amount of substance dissolved in water and is carried by osmosis.
4. If the medium surrounding the cell has higher water concentration than the cell (i.e. hypotonic solution), more water moves inside the cell than will leave.
5. If the medium id hypertonic (low water concentration inside and outside the cell) same amount of water moves outside the cell as moves inside. Thus there is no net movement of water.
Q. What would happen to the life of a cell if there was no Golgi apparatus?
A. If there were no Golgi apparatus in the cell then :
1. The material synthesised near the ER will not be packaged and dispatched to various targets inside and outside the cell.
2. The storage, modification and packaging of products in vesicles will not take place.
3. In some cells, complex sugars would not be made from simple sugars.
4. Lysosomes will not be formed.
A.
Q. Differentiate between:
1. Prokaryotic cell and eukaryotic cell.
A.
4. Smooth ER and rough ER
Q. Explain how Golgi bodies are related to ER.
A. Both Golgi bodies and ER are involved in membrane biogenesis. The proteins manufactured by the ER are packed by the Golgi bodies into vesicles and sent to the target site (periphery of the cell) where they arrange to form the membrane. Hence ER and Golgi bodies are related.
Q. What are lysosomes? How do they digest their own cells?
A. Lysosomes are waste disposal organelles of the cell containing digestive enzymes. During the disturbance in the cell metabolism, lysosomes burst and the digestive enzymes thus released, digest their own cell.
Q. What is plasmolysis?
A. When a living plant cell loses water through osmosis, there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.
Q. Do dead cells also exhibit osmosis? Why or why not?
A. Osmosis is a special case of diffusion through a selectively permeable membrane. Dead cells do not a selectively permeable membrane. Thus dead cells don't exhibit osmosis.
Q. What is endocytosis? How is it important to an organism?
A. Endocytosis is the ingestion of material by the cells through the plasma membrane. It is important because it allows cell to engulf food and other necessary materials from its external environment. For example, Amoeba acquires its food through endocytosis.
Q. How does each cell acquire structure and ability to function?
A. Each cell acquires structure and ability to function because of the organisation of its membrane and cell organelles in specific ways.
Q. Describe in detail, the internal structure of the nucleus.
A. 1. NUCLEAR MEMBRANE- It is double layered membrane separating cytoplasm and nucleoplasm.
2. NUCLEOPLASM- The fluid present in nucleus, It is similar to cytoplasm.
3. NUCLEOPORE- These are pores that allow the transfer of material from inside of the nucleus to outside.
4.NUCLEOLUS- The small spherical body. It contains RNA and manufactures proteins.
5. CHROMATIN/CHROMOSOMES- Chromatin is the entangled mass of thread like structures. It contains DNA and proteins. During cell division, it is visible as rod like structures called chromosomes and is responsible for inheritance.
A. 1. Each cell can perform the basic life functions.
2. There is division of labour in each cell.
3. Every cell has got certain specific components within it, known as cell organelles. Each kind of cell organelle performs a specific function.
4. A cell is able to live and perform all its functions because of these organelles.
5. All of cells have the same organelles, no matter what their function is or what organism they are found in.
Q. Give an example of a cell that has the following:
1. Fixed shape- RBC
2. Ever changing shape- WBC
3. Typical shape- Nerve cell
Q. Who discovered cell and how?
A. Cells were discovered by Robert Hooke. He observed dead cells in a cork slice with the help of a primitive microscope.
Q. What is the cell made up of?
A. Composition of the cell is as follows
1. Proteins
1. Proteins
2. Fats
3. Carbohydrates
4. Vitamins
5. Minerals
6. Inorganic salts
4. Vitamins
5. Minerals
6. Inorganic salts
7. Water
Q. Who gave the cell theory and what are the postulates of the same?
A. The cell theory was given by Schleiden and Schwann.
It states that:
1. All living organisms are made up of cells.
2. Cell is the basic unit of life.
3. All cells arise from pre-existing cells(given by Virchow).
Q. What is the advantage of the shape of the following cells? Also mention the shapes.
A.1. Nerve cell: Elongated and branched. This shape helps to carry messages between body parts the brain and also in the control and coordination of body parts.
2. RBC: Biconcave and disk shaped. This shape allows the RBC to hold large amount of haemoglobin in them, so that more oxygen can be transported to different parts of the body.
3. Fat cell: Large and globular. This shape helps to store food, provide insulation to the body and act as shock absorbers.
4. Muscle cell: Spindle shaped. It helps in relaxation and contraction of muscle so as to bring movement.
5. Sperm cell: Conical head and a tail. The head helps to pierce through the wall of ovum in order to begin fertilization and tail provides mobility as ovum in non-motile.
6. Ovum: Large and oval. It provides more surface area for sperm to pierce through.
Q. Why cells of plants, fungi and bacteria do not burst when kept in external media?
A. Cells of plants, fungi and bacteria do not burst when kept in external media because of the presence of cell wall. When these are kept in hypotonic external media, they take water by osmosis and swell up. This builds up pressure against the cell wall. The cell wall exerts equal pressure against the swollen cell, thus preventing it from bursting.
Q. Which organelle is known as the powerhouse of the cell and why ?
A. Mitochondria are known as the powerhouse of the cell. They release energy required for various chemical activities needed for life in the form of ATP(Adenosine Tri Phosphate).
Q. What are lysosomes? How do they digest its own cell?
A. Lysosomes are the waste disposal organelles of the cell containing digestive enzymes. During the disturbance in the cell metabolism lysosomes burst and the enzymes thus released digest their own cell.
Q. How materials are transported across cell membrane?
A. 1. Gases like CO2 (cellular waste and is to be excreted by the cell) accumulate in high concentration inside the cell. A soon as there is difference in concentration of CO2 inside and outside the cell i.e. low concentration outside, CO2 moves out of the cell by diffusion.
2. Similarly O2 enters the cell by diffusion when concentration of O2 inside the cell decreases.
3. The movement of water across the plasma membrane is affected by the amount of substance dissolved in water and is carried by osmosis.
4. If the medium surrounding the cell has higher water concentration than the cell (i.e. hypotonic solution), more water moves inside the cell than will leave.
5. If the medium id hypertonic (low water concentration inside and outside the cell) same amount of water moves outside the cell as moves inside. Thus there is no net movement of water.
Q. What would happen to the life of a cell if there was no Golgi apparatus?
A. If there were no Golgi apparatus in the cell then :
1. The material synthesised near the ER will not be packaged and dispatched to various targets inside and outside the cell.
2. The storage, modification and packaging of products in vesicles will not take place.
3. In some cells, complex sugars would not be made from simple sugars.
4. Lysosomes will not be formed.
Q. Make a comparison and write down ways in which plant cells are different from animal cells.
A.
| PLANT CELL |
ANIMAL CELL
|
Large central sap vacuole present.
|
Small numerous food and contractile vacuoles present.
|
Cell wall is present.
|
Cell wall is absent.
|
Contains plastids
|
Does not contain plastids.
|
Nucleus is at the periphery.
|
Nucleus is in the centre.
|
Cannot burst in hypotonic solution.
|
Can burst in hypotonic solution.
|
|
PROKARYOTIC CELL
|
EUKARYOTIC CELL
|
|
Size is generally small. (1-10pm)
|
Size is generally large. (5-100 pm)
|
|
Lacks well defined nucleus with nuclear membrane and is known as nucleoid.
|
Well defined nucleus with nuclear membrane.
|
|
Single chromosome is present
|
More than one chromosome is present.
|
|
Membrane bound organelles are absent.
|
Membrane bound organelles are present.
|
2. Nucleus and nucleoid.
A.
|
NUCLEAS
|
NUCLEOID
|
|
Nuclear membrane is present.
|
Nuclear membrane is absent.
|
|
It is present in eukaryotic cells.
|
It is present in prokaryotic cells.
|
|
More than one chromosome is present.
|
Single chromosome is present.
|
3. Chromatid, chromosomes and chromatin.
A.
|
CHROMATID
|
CHROMOSOMES
|
CHROMATIN
|
|
These are the arms of the chromosomes.
|
Thread like structures visible only during cell division.
|
It is the thin, thread like intertwined mass which consists of DNA and proteins.
|
A.
SMOOTH ER
|
ROUGH ER
|
|
Looks smooth as no ribosomes are attached to its surface.
|
Looks rough as ribosomes are attached to its surface.
|
|
Helps in the manufacture of fat molecules/lipids.
|
Helps in manufacture of proteins (because it contains proteins).
|
|
It is connected to either plasma membrane or nuclear membrane.
|
It is connected to both, plasma and nuclear membrane.
|
Q. Explain how Golgi bodies are related to ER.
A. Both Golgi bodies and ER are involved in membrane biogenesis. The proteins manufactured by the ER are packed by the Golgi bodies into vesicles and sent to the target site (periphery of the cell) where they arrange to form the membrane. Hence ER and Golgi bodies are related.
Q. What are lysosomes? How do they digest their own cells?
A. Lysosomes are waste disposal organelles of the cell containing digestive enzymes. During the disturbance in the cell metabolism, lysosomes burst and the digestive enzymes thus released, digest their own cell.
Q. What is plasmolysis?
A. When a living plant cell loses water through osmosis, there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.
Q. Do dead cells also exhibit osmosis? Why or why not?
A. Osmosis is a special case of diffusion through a selectively permeable membrane. Dead cells do not a selectively permeable membrane. Thus dead cells don't exhibit osmosis.
Q. What is endocytosis? How is it important to an organism?
A. Endocytosis is the ingestion of material by the cells through the plasma membrane. It is important because it allows cell to engulf food and other necessary materials from its external environment. For example, Amoeba acquires its food through endocytosis.
Q. How does each cell acquire structure and ability to function?
A. Each cell acquires structure and ability to function because of the organisation of its membrane and cell organelles in specific ways.
Q. Describe in detail, the internal structure of the nucleus.
A. 1. NUCLEAR MEMBRANE- It is double layered membrane separating cytoplasm and nucleoplasm.
2. NUCLEOPLASM- The fluid present in nucleus, It is similar to cytoplasm.
3. NUCLEOPORE- These are pores that allow the transfer of material from inside of the nucleus to outside.
4.NUCLEOLUS- The small spherical body. It contains RNA and manufactures proteins.
5. CHROMATIN/CHROMOSOMES- Chromatin is the entangled mass of thread like structures. It contains DNA and proteins. During cell division, it is visible as rod like structures called chromosomes and is responsible for inheritance.
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