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


  • 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


  • 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


  • 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
Surface Volume Ratio of Image - 1 for Cell Introduction
Surface Volume Ratio of Image - 2 for Cell Introduction
Surface Volume Ratio of Image - 3 for Cell Introduction

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)

Frequently Asked Questions (FAQs)

  • zacharias janssen translate in sindhi

    ( - kk...@ on )

    1 Answer

    To translate the contents into Sindhi you just need to visit the same link.Once the page is open look at the bottom corner of the rightmost side of page.You will see an option called Translate,just click on it.Then at the leftmost bottom corner of the page u will get a pop up 'select language'.From there you can choose the language of your choice.

    - kk...@ on

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