Cell Introduction YouTube Lecture Handouts
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Cell Introduction YouTube Lecture Handouts
Cell: An Introduction

Structure of Cell for Cell Introduction of Image -1
Structure of Cell For Cell Introduction of Image -1
Introduction
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Lamarck: no body can have life, if no cells
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Cytology: Study of form, structure & composition of cell
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Cell Biology: Deals with structure, chemistry & functioning of cell
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Unicellular: Amoeba, bacteria, yeast, acetabularia – independent existence & perform all essential functions
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Multicellular: made of many cells (new born infant - cells to 100 trillion in 60 kg man)
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Large organism – not have large-sized cells but more cells
Cell
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Structural unit
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Functional Unit
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Building blocks
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Smallest unit capable of independent existence
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Totipotent: Single cell can form whole organism
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Cell Tissue Organ Organ System (division of labour)
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Pasteur – life originates from life
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Haeckel – nucleus stores and transmits hereditary
Microscope
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1st by Zacharias Janssen – 1590
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Modified by Galileo
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Then by Robert Hooke – new microscope – study of cork cells
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Hooke – book – Micrographia- honey comb structure called it cellula
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Malphighi – called it saccules & utricles
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Leeuwenhoek – 1st to observe, describe & sketch free living cell
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Robert Brown – disc. nucleus in cell
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Dujardin – living semifluid substance as sarcode
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Purkinje & von Mohl – called sarcode as protoplasm
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Schwann – disc. cell membrane
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Nageli & Cramer – named it as cell membrane
Cell Theory
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By Schleiden & Schwann
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Schwann – animal cells don’t have cell wall
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Organism made of cells
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Cells are units of structure and function of living organisms
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New cells from pre-existing cells
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Each cell has protoplasm
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All cells are alike in chemistry & physiology
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Activity of organism are sum total of activities of cell
Modern Cell Theory or Cell Doctrine
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All living beings have cells
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Cells are units of structure & function
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Cell can survive independently, organelle cannot
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Cells have fundamental similarity
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Life exists in cells
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Cells can be modified (elongated in muscle & nerve cell)
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Cell grows & multiplies
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Life passes to next generation as cell
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New cells from pre-existing cells
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All cells have common ancestry
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Cells are totipotent
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No organism can have activity that is absent in its cell
Objections to Modern Cell Theory
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Virus are a cellular
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Some organisms – body is not differentiated in cells (e.g. rhizopus)
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Protozoa have uninucleate differentiated body
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Bacteria & cyanobacteria don’t have nucleus
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RBCs & sieve tube cells are without nucleus
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In skin & cork – protoplasm is replaced by nonliving material
Surface Volume Ratio
Small cells – higher surface volume ratio

Surface Volume Ratio of Image - 1 for Cell Introduction
Surface Volume Ratio of Image - 1 For Cell Introduction

Surface Volume Ratio of Image - 2 for Cell Introduction
Surface Volume Ratio of Image - 2 For Cell Introduction

Surface Volume Ratio of Image - 3 for Cell Introduction
Surface Volume Ratio of Image - 3 For Cell Introduction
Types of Cells
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Undifferentiated / Stem Cells: Unspecialized and have power of division – stem apical meristem
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Differentiated / Post-mitotic Cells: Specialized for better organization and avoid duplication
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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
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Separation from extracellular medium
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Selective permeability
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Accumulation
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Interconnections
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Recognition
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Communication & exchange
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Intracellular compartmentalization
Cell Sizes
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Smallest cell – Mycoplasma
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RBC is 7 in diameter
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Lymphocytes are 6
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Kidney, liver and intestine are 20-30
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Longest human cell – nerve cell of 90 cm
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Egg cells are large sized cells – store food for embryo
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Avian eggs are largest
Cell Shapes
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Surface cells – flat
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Cortex – polygonal
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RBC – biconcave
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Nerve cells – long
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Sperms – tail for mobility
Prokaryotic & eukaryotic cells (to be discussed in next lesson)
-Manishika