L2 | CELL THEORY

• TRADITIONAL CELL THEORY

  1. all living organisms are made of one or more cells.
  2. cells are the basic units of structure and function in all living things.
  3. cells come only from pre-existing cells.
• ARISTOTLE (334 BCE)

  • Sets the standard for biology
  • Observe nature directly 
  • Classified all known organisms on either plants / animals
• PLANTS

  • Non-mobile but color green
• ANIMALS

  • In terms of habitat: terrestrial, aquatic, aerial
• HANS AND ZACHARIAS JANSSEN (1595)

  • Produced the first compound microscope by lining up 2 lenses
  • Marketed their product to scientist
• ROBERT HOOKE (1665)

  • Set the trend about cells
  • Observed living matter from a piece of cork through a compound microscope, revealing empty cells.
  • Described it as consisting of “a great many little boxes”
  • Little boxes reminded him of the cubicles or “cells” in which monks lived, so he called them cells.
• ROBERT HOOKE (1665)

  • First to call the spaces in the cork “cells” = little rooms
  • “Cellula”= tiny compartment with boundaries
  • described the cells as tiny boxes or a honeycomb 
  • He thought that cells only existed in plants and fungi
  • Observed the remains of a dead plant cells
• ANTON VAN LEEUWENHOEK (1673)

  • Used a handmade microscope to observe pond scum & discovered single-celled organisms
  • observed blood cells from fish, birds, frogs, dogs, and humans
  • was the first to observe living cells in microorganisms;
  • called these organism animalcules ~ we now call them protists.
• ANTON VAN LEEUWENHOEK (1673)

  • Considered the “Father of Microbiology”
• 150-200 YEAR GAP

  • Between the Hooke / Leeuwenhoek discoveries and the mid 19th century, very little cell advancements were made.
• 19TH CENTURY ADVANCEMENT

  • Much doubt existed around Spontaneous Generation and was conclusively disproved by Louis Pasteur
• MATTHIAS SCHLEIDEN (1838)

  • German botanist, concluded that all plant parts are made of cells
• THEODOR SCHWANN (1839)

  • German physiologist stated that all animal tissues are composed of cells.
• RUDOLPH VIRCHOW (1858)

  • German physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells.
  • Tested with his skin
  • Opened the door for cellular reproduction.
• MODERN CELL THEORY

  1. The cell contains hereditary information (DNA) which is passed on from cell to cell during cell division.
  2. All cells are basically the same in chemical composition and metabolic activities.
  3. All basic chemical & physiological functions are carried out inside the cells.
  4. Cell activity depends on the activities of sub-cellular structures within the cell
• CELLS

  Basic unit of life
• SINGLE CELLS

  • Microorganisms such as bacteria, yeast, and amoebae
• • Adult human is made up of about 30 trillion cells (1 trillion = 10^12) which are mostly organized into collectives called tissues.
• CELL SHAPE

  • reflects its function.
• CELL SIZE

  • limited by a cell’s surface area–to volume ratio.
  • differs amongst species
  • Unicellular organisms are made up of one cell. 
  • Multicellular organisms are made up of many cells that often specialize according to function.
• PROKARYOTIC CELLS

  • said to be prokaryotic (Greek for “before nucleus”) because they have very little visible internal organization so that, for instance, the genetic material is free within the cell.
  • small, the vast majority being 1-2 µm in length.
• EUKARYOTIC CELLS

  • eukaryotic (Greek for “with a nucleus”).
  • generally larger (5-100 µm, although some eukaryotic cells are large enough to be seen with the naked eye) and structurally more complex.
  • contain a variety of specialized structures known collectively as organelles, surrounded by a viscous substance called cytosol. 
• PROKARYOTIC

  • earth's first cell
  • includes bacteria
  • Can survive in a variety of environments 
  • Earth’s most abundant inhabitants and the simplest cellular life form.
  • Largest group
  • Lack nuclei and membrane-bound organelles