Cell Introduction YouTube Lecture Handouts

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Cell Introduction YouTube Lecture Handouts

Cell: An Introduction

Illustration: 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
Illustration: Surface Volume Ratio
Illustration: Surface Volume Ratio
Illustration: 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

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