The Unit of Life (Cell)
Topic to be covered
- Introduction
- Cell theory
- Prokaryotic vs eukaryotic
- Eukaryotic cell structure
- Cell membrane
- Cell wall
- Endoplasmic Reticulum
- Golgi apparatus
- Ribosome
- Lysosome
- Vacuoles
- Mitochondria
- Plastids
- Cytoskeleton
- Cilia and flagella
- Centrioles
- Nucleus
5. Prokaryotic cell structure
Introduction of cell
The cell is a building block of all living organisms.
Discovery of the cell.
The cell is discovered by Robert Hooke in 1665. On viewing the thin cutting of cork, he discovers empty spaces contained by walls. Resembled honeycomb structure. These spaces called cells.
Evolution of cell theory
- The first cell is discovered by Robert Hooke in 1665
- the nucleus in a cell is discovered by Robert Brown in 1833.
- Cell theory is purposed by Scheiden and Schwann in 1839. ( Cell is the structural and functional unit of life).
- Cell arise fr pre-existing cell is told by Virchow in 1855.
Cell theory
- The cell is the structural and functional unit of life.
- All organisms in the earth made up of cells.
- All cells arise from pre-existing cells only.
- The nucleic acid is the genetic material in all cells.
- Cells interact with each other which results in the organism's functional Example: Digestive system.
- Basic chemical composition is more/less same in all cells.
Organization within the cell
Example: you have one plate of fruits, vegetables, and flowers. They are not arranged correctly and if somebody wants only fruits. Somebody wants only vegetables and somebody wants only flowers. It is really difficult because it was measured on a plate. But if you want arrange in some plate dividing into the compartment. So compartment makes thing more organized.
Compartment of cell
- Nucleolus
- Nucleus
- Ribosomes
- Vesicle
- Rough endoplasmic Reticulum
- Golgi apparatus
- Cytoskeleton
- Smooth endoplasmic Reticulum
- Mitochondria
- Vacuole
- Cytosol
- Lysosome
- Centrioles within centrosome
- Cell membrane
Cell type
Bases on internal complexity it is two types
- Prokaryotic cell
- Eukaryotic cell
Prokaryotic cell
In this cell Membrane-bounded cell organelles are absent
Example: bacteria, Archaebacteria.
Eukaryotic cell
In this cell membrane-bound organelles are present
Examples: plant cell, animal cell, fungi, protists.
Compartmentalization is seen in eukaryotic cells.
Size of cells
Cells exist in a variety of shapes and sizes.
Shapes of cells
The shape of cells varies with the functions which they perform.
Classification of organisms bases on the number of cells
- Unicellular organisms: single cells organisms called unicellular organisms.
- Multicellular organisms: multiple cell organisms called multiplecellular organisms.
Unicellular organisms
- Single-cell constitute the organism
- Single-cell performs the basic functions that are characteristics of organisms cell has changed shape
- Example: Amoeba, Chlamydomonas, paramecium, bacteria.
Multiple cellular organisms
- Multi cells constitute the organism.
- There is a division of labor in multicellular organisms.
- Some organisms have cells of various kinds.
Eukaryotic cells
Characteristics
- Membrane-bound organelles are present.
- Cell compartmentalization is present
- Membrane-bound nucleus is present.
- Locomotive and cytoskeleton structures are present.
- Genetic material is well organized.
Where do we see eukaryotic cells?
- Kingdom protists
- Fungi
- Plantar
- Animalia
What are cell organelles?
- A cell is made up of components called cell organelles.
- A cell bus able to live and perform all its functions because of these organelles.
- All cells have less/more same organelles, irrespective of their function and organism they are found in.
- Same as compartmentalization of cell.
Difference between plant cell and animal cell?
Plant cell
- the cell wall is present
- Vacuoles are big and lesser in number.
- Plastids are present.
- Simple distributed Golgi apparatus lysosomes
- Centrioles are absent
- Large in size
Animal cell
- The cell wall is absent
- Vacuoles are many and small (not necessarily all animal cells have it).
- Plastids are absent (exception: euglena)
- Single complex prominent Golgi apparatus.
- Centrioles are present.
- Small in size.
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Experiment with a sample of onion peel
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Structure of a cell
Plasma membrane
- Plasma membrane/cell membrane
- Cell wall (only in plant cells)
- Nucleus
- Cytoplasm
- Cell organelles
Cell membrane
- It is thin, delicate and living in an outermost covering of the cell.
- It ensures the protection of the cell.
- It is a selectively permeable membrane
Plasma membrane: Selectively permeable membrane
Movement of substance in and out of the cell
Diffusion
The gaseous exchange between cells as a cell and it's the external environment.
Osmosis
The Water exchange between cells as a cell and it's the external environment.
Plasma membrane: Active and passive transport
Transport
It is Movement of molecules across the plasma membrane.
Two modes of transport
- Passive transport
- Active transport
Plasma membrane: passive transport
- Passive transport is the movement of the molecules across the membrane that require no energy from the cell.
- The movement occurs along the concentration gradient by diffusion/osmosis.
Two types of diffusion can take place
Simple diffusion
- Particles directly move across the membrane.
- Facilitated diffusion
- The transport protein help particles move across the membrane.
Plasma membrane: active transport
- Movement of molecules across membrane require energy from cell.
- Movement occurs against the concentration gradient.
- Carrier protein of the cell membrane act as a pump.
- ATP provides the energy input from the cell.
Plasma membrane structure
- The plasma membrane is made of lipids and proteins.
- Structure saw only through an electron microscope.
- Lipid bilayer structure.
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