Cell Introduction YouTube Lecture Handouts
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Cell Introduction YouTube Lecture Handouts
Cell: An Introduction
Introduction
- Lamarck: no body can have life, if no cells
- Cytology: Study of form, structure & composition of cell
- Cell Biology: Deals with structure, chemistry & functioning of cell
- Unicellular: Amoeba, bacteria, yeast, acetabularia – independent existence & perform all essential functions
- Multicellular: made of many cells (new born infant - cells to 100 trillion in 60 kg man)
- Large organism – not have large-sized cells but more cells
Cell
- Structural unit
- Functional Unit
- Building blocks
- Smallest unit capable of independent existence
- Totipotent: Single cell can form whole organism
- Cell Tissue Organ Organ System (division of labour)
- Pasteur – life originates from life
- Haeckel – nucleus stores and transmits hereditary
Microscope
- 1st by Zacharias Janssen – 1590
- Modified by Galileo
- Then by Robert Hooke – new microscope – study of cork cells
- Hooke – book – Micrographia- honey comb structure called it cellula
- Malphighi – called it saccules & utricles
- Leeuwenhoek – 1st to observe, describe & sketch free living cell
- Robert Brown – disc. nucleus in cell
- Dujardin – living semifluid substance as sarcode
- Purkinje & von Mohl – called sarcode as protoplasm
- Schwann – disc. cell membrane
- Nageli & Cramer – named it as cell membrane
Cell Theory
- By Schleiden & Schwann
- Schwann – animal cells don՚t have cell wall
- Organism made of cells
- Cells are units of structure and function of living organisms
- New cells from pre-existing cells
- Each cell has protoplasm
- All cells are alike in chemistry & physiology
- Activity of organism are sum total of activities of cell
Modern Cell Theory or Cell Doctrine
- All living beings have cells
- Cells are units of structure & function
- Cell can survive independently, organelle cannot
- Cells have fundamental similarity
- Life exists in cells
- Cells can be modified (elongated in muscle & nerve cell)
- Cell grows & multiplies
- Life passes to next generation as cell
- New cells from pre-existing cells
- All cells have common ancestry
- Cells are totipotent
- No organism can have activity that is absent in its cell
Objections to Modern Cell Theory
- Virus are a cellular
- Some organisms – body is not differentiated in cells (e. g. rhizopus)
- Protozoa have uninucleate differentiated body
- Bacteria & cyanobacteria don՚t have nucleus
- RBCs & sieve tube cells are without nucleus
- In skin & cork – protoplasm is replaced by nonliving material
Surface Volume Ratio
- Small cells – higher surface volume ratio
Types of Cells
- Undifferentiated⟋Stem Cells: Unspecialized and have power of division – stem apical meristem
- Differentiated⟋Post-mitotic Cells: Specialized for better organization and avoid duplication
- Dedifferentiated Cells: Differentiated cell which revert to undifferentiated state and loose specialization - cork cambium of plant, healing of wound, regeneration in animals and vegetative propagation in plants
Compartmentalization of Cellular Life
- Separation from extracellular medium
- Selective permeability
- Accumulation
- Interconnections
- Recognition
- Communication & exchange
- Intracellular compartmentalization
Cell Sizes
- Smallest cell – Mycoplasma
- RBC is 7 in diameter
- Lymphocytes are 6
- Kidney, liver and intestine are 20 - 30
- Longest human cell – nerve cell of 90 cm
- Egg cells are large sized cells – store food for embryo
- Avian eggs are largest
Cell Shapes
- Surface cells – flat
- Cortex – polygonal
- RBC – biconcave
- Nerve cells – long
- Sperms – tail for mobility
Prokaryotic & eukaryotic cells (to be discussed in next lesson)
- Dr. Manishika Jain, NTSE Scholar, UGC NET JRF, CSIR NET JRF Gold Medalist, Jawaharlal Nehru University, Delhi
✍ Manishika