CBSE Quick Revision Notes
CBSE Class-11 Biology
CHAPTER-08
CELL: STRUCTURE AND FUNCTIONS
• Study of form, structure, and composition of cell is called cytology.
• Cell is the structural and functional unit of life. In unicellular organism (amoeba, paramecium,
yeast, bacteria) single cell performs all the essential functions of life.
• In multicellular organism, different kinds of tissues perform different function and have division
of labour.
• Anton Von Leeuwenhoek first saw and described a live cell. Robert Brown later discovered the
nucleus.
• Metthias Schleiden and Theodore Schwann( 1938) proposed the cell theory which was later
modified by Rudolf Virchow(1855)-
1. All living organisms are composed of cells and products of cells.
2. All cells arise from pre-existing cells.
Prokaryotic cells Eukaryotic cells
1. Membrane bound nucleus is absent. 1. Membrane bound nucleus is present.
2. Cells are smaller in size. 2. Cells are larger in size.
3. Single chromosome is present. 3. More than one chromosome is present.
4. Membrane bound organelles are absent. 4. Membrane bound organelles are present.
Shape and size of cells varies greatly according to their position and function. Mycoplasma is the
smallest cell and largest isolated cell is the ostrich egg. The shape of cell may be cuboid, columnar,
polygonal, thread like or irregular.
Prokaryotic Cells
• Prokaryotic cells are represented by Bacteria, Blue green algae, Mycoplasma and PPLO. They
multiply rapidly and vary in size greatly.
• Bacterial cells may be Bacillus (rod shaped), Coccus (spherical), Vibrio (comma-shaped) and
Spirillum (spiral).
• All prokaryotic cells have cell wall surrounding the cell membrane except in Mycoplasma.
Genetic material is naked.
• The plasmid DNA, in some bacteria provides some special features like resistance to
antibiotics.
• Cell organelles like Mitochondria, Golgi bodies etc. are absent in prokaryotes. A specialized
differentiated cell membrane called Mesosome is the characteristic of prokaryotes.
, • In bacterial cell a chemically complex cell envelope is present, which consist of three layers.
The outermost is Glycocalyx, middle one cell wall and inner innermost is the cell membrane.
• Glycocalyax may be as loose sheath in some bacteria called slime layer. In some other
bacteria Glycocalyx may be thick and tough called capsule.
• Plasma membrane is semi-permeable having mesosome in the form of vesicles, tubules and
lamellae. They help in cell wall formation, DNA replication and distribution to daughter cells.
• Motile bacterial cell contain flagella, which is composed of filament, hook and basal body. Pili
and fimbriae are the other surface structures that help the bacteria to attach with host and
other substances.
• In prokaryotes, ribosome are attached with cell membrane having two sub-units – 50S and
30S to form together 70S prokaryotic ribosomes.
• Ribosomes are site of protein synthesis. Ribosomes attached with mRNA to form a chain are
called polyribosomes.
• Reserved materials in prokaryotic cells are present in cytoplasm as cell inclusion bodies, which
may contain phosphate, granules, glycogen granules etc.
• Gas vacuoles are found in blue green algae and purple and green photosynthetic bacteria.
Eukaryotic Cell
• Eukaryotic cells are present in Protista, plants, Animals and Fungi. Cytoplasm is divided into
compartments due to presence of membrane bounded organelles.
• The cells contain well organized nucleus with nuclear membrane. The genetic materials are
arranged in chromosomes.
• Plants cells differ in having cell wall, plastids and large central vacuole as compared to animal
cells. Animal cells have centrioles, which are absent in plant cells.
CBSE Class-11 Biology
CHAPTER-08
CELL: STRUCTURE AND FUNCTIONS
• Study of form, structure, and composition of cell is called cytology.
• Cell is the structural and functional unit of life. In unicellular organism (amoeba, paramecium,
yeast, bacteria) single cell performs all the essential functions of life.
• In multicellular organism, different kinds of tissues perform different function and have division
of labour.
• Anton Von Leeuwenhoek first saw and described a live cell. Robert Brown later discovered the
nucleus.
• Metthias Schleiden and Theodore Schwann( 1938) proposed the cell theory which was later
modified by Rudolf Virchow(1855)-
1. All living organisms are composed of cells and products of cells.
2. All cells arise from pre-existing cells.
Prokaryotic cells Eukaryotic cells
1. Membrane bound nucleus is absent. 1. Membrane bound nucleus is present.
2. Cells are smaller in size. 2. Cells are larger in size.
3. Single chromosome is present. 3. More than one chromosome is present.
4. Membrane bound organelles are absent. 4. Membrane bound organelles are present.
Shape and size of cells varies greatly according to their position and function. Mycoplasma is the
smallest cell and largest isolated cell is the ostrich egg. The shape of cell may be cuboid, columnar,
polygonal, thread like or irregular.
Prokaryotic Cells
• Prokaryotic cells are represented by Bacteria, Blue green algae, Mycoplasma and PPLO. They
multiply rapidly and vary in size greatly.
• Bacterial cells may be Bacillus (rod shaped), Coccus (spherical), Vibrio (comma-shaped) and
Spirillum (spiral).
• All prokaryotic cells have cell wall surrounding the cell membrane except in Mycoplasma.
Genetic material is naked.
• The plasmid DNA, in some bacteria provides some special features like resistance to
antibiotics.
• Cell organelles like Mitochondria, Golgi bodies etc. are absent in prokaryotes. A specialized
differentiated cell membrane called Mesosome is the characteristic of prokaryotes.
, • In bacterial cell a chemically complex cell envelope is present, which consist of three layers.
The outermost is Glycocalyx, middle one cell wall and inner innermost is the cell membrane.
• Glycocalyax may be as loose sheath in some bacteria called slime layer. In some other
bacteria Glycocalyx may be thick and tough called capsule.
• Plasma membrane is semi-permeable having mesosome in the form of vesicles, tubules and
lamellae. They help in cell wall formation, DNA replication and distribution to daughter cells.
• Motile bacterial cell contain flagella, which is composed of filament, hook and basal body. Pili
and fimbriae are the other surface structures that help the bacteria to attach with host and
other substances.
• In prokaryotes, ribosome are attached with cell membrane having two sub-units – 50S and
30S to form together 70S prokaryotic ribosomes.
• Ribosomes are site of protein synthesis. Ribosomes attached with mRNA to form a chain are
called polyribosomes.
• Reserved materials in prokaryotic cells are present in cytoplasm as cell inclusion bodies, which
may contain phosphate, granules, glycogen granules etc.
• Gas vacuoles are found in blue green algae and purple and green photosynthetic bacteria.
Eukaryotic Cell
• Eukaryotic cells are present in Protista, plants, Animals and Fungi. Cytoplasm is divided into
compartments due to presence of membrane bounded organelles.
• The cells contain well organized nucleus with nuclear membrane. The genetic materials are
arranged in chromosomes.
• Plants cells differ in having cell wall, plastids and large central vacuole as compared to animal
cells. Animal cells have centrioles, which are absent in plant cells.
