Most prokaryotic cells, particularly the bacterial cells, have a chemically complex ______.
Explanation
Most bacterial cells possess a chemically complex cell envelope.
The cell envelope consists of three layers: glycocalyx, cell wall and plasma membrane.
These layers work together to protect the cell and maintain its structure.
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Conclusion
The chemically complex cell envelope is characteristic of most bacterial cells.
2
The cell envelope consists of a tightly bound ______ layered structure i.e., ______.
Explanation
The bacterial cell envelope consists of three tightly bound layers.
From outside to inside, the layers are glycocalyx, cell wall and plasma membrane.
These layers provide protection and help maintain the shape of the bacterial cell.
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Conclusion
The bacterial cell envelope has three layers: glycocalyx, cell wall and plasma membrane.
3
Although each layer of the envelope performs ______, they act together as a ______.
Explanation
Each layer of the bacterial cell envelope has a distinct function.
The glycocalyx, cell wall and plasma membrane work together.
Together, they provide protection and help maintain cell integrity.
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Conclusion
The three layers perform distinct functions but act together as a single protective unit.
4
Bacteria can be classified into ______ groups on the basis of the differences in the cell envelopes and the manner in which they respond to the ______ procedure developed by ______ viz., those that take up the gram stain are ______ and the others that do not are called ______ bacteria.
Explanation
Bacteria are classified into two groups based on their cell envelope structure and Gram-staining response.
The Gram-staining procedure was developed by Hans Christian Gram.
Gram-positive bacteria retain the primary stain and appear purple.
Gram-negative bacteria do not retain the primary stain and appear pink after counterstaining.
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Conclusion
Bacteria are classified as Gram-positive and Gram-negative based on Gram staining.
5
Glycocalyx differs in ______ and ______ among different bacteria.
Explanation
The glycocalyx is the outermost layer of the bacterial cell envelope.
Its chemical composition and thickness vary among different bacteria.
Based on its nature, the glycocalyx may be a loose slime layer or a thick, tough capsule.
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Conclusion
Glycocalyx varies in composition and thickness among different bacteria.
6
Glycocalyx could be a loose sheath called the ______ in some, while in others it may be thick and tough, called the ______.
Explanation
The glycocalyx is the outermost layer of the bacterial cell envelope.
When it is loosely organised, it is called the slime layer.
When it is thick and tough, it is called the capsule.
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Conclusion
The glycocalyx occurs as a loose slime layer or a thick, tough capsule.
7
The cell wall determines the ______ of the cell and provides a ______ to prevent the bacterium from ______.
Explanation
The bacterial cell wall determines the shape of the cell.
It provides strong structural support and maintains cell integrity.
It prevents the bacterium from bursting or collapsing due to changes in osmotic pressure.
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Conclusion
The bacterial cell wall maintains cell shape, provides structural support and prevents bursting or collapsing.
8
The plasma membrane is ______ in nature and interacts with the outside world.
Explanation
The plasma membrane is selectively permeable in nature.
It allows certain substances to enter or leave the cell while restricting others.
This helps the cell regulate the exchange of materials with its surroundings.
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Conclusion
The plasma membrane is selectively permeable and regulates the movement of substances into and out of the cell.
9
This membrane is similar structurally to that of the ______.
Explanation
The bacterial plasma membrane is structurally similar to the plasma membrane of eukaryotic cells.
Both membranes are primarily composed of a lipid bilayer with associated proteins.
Both regulate the movement of substances into and out of the cell.
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Conclusion
The plasma membrane of prokaryotes is structurally similar to that of eukaryotes.
10
A special membranous structure is the ______ which is formed by the extensions of plasma membrane into the cell.
Explanation
Mesosomes are described in NCERT as specialised structures formed by infoldings of the plasma membrane.
They may appear as vesicles, tubules and lamellae.
Note: Mesosomes are historically described structures; modern research considers them artefacts produced during chemical fixation.
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Conclusion
Mesosomes are described as infoldings or extensions of the plasma membrane in prokaryotes.