Biology Chapter: The Cell and its Discovery

The Cell and its Beginning

• Life originated as primitive cells, called protocells, from inorganic and organic molecules in Earth's prebiotic oceans.
• This occurred approximately 3.5 to 4 billion years ago.
• Mitochondria are believed to have evolved from bacteria that were incorporated into larger cells.

How Did Scientists Discover Cells?

• Robert Hooke (1635-1703) was the first to describe cells.

• He observed cork cells using a microscope and noted their honeycomb-like structure.

• He termed the structures "cells" because they resembled the small rooms where monks lived.

• Hooke's observations were published in Micrographia in 1665.

• Anton van Leeuwenhoek (1632-1723) discovered and described bacteria and other microorganisms.

• Leeuwenhoek created simple microscopes with single lenses, capable of magnifying objects up to 270 times.

• He observed living cells in pond water, blood, and other samples.

The Cell Theory

• Matthias Jakob Schleiden (1804-1881) focused on studying plant cells.
• Theodor Schwann (1810-1862) studied animal cells.
• Both Schleiden and Schwann confirmed that cells are the fundamental units of life and every living organism consists of one or more cells.
• Rudolf Carl Virchow (1821-1902), in 1858, proposed that all cells originate from pre-existing cells.

Cell Theory Summary

• All organisms are composed of one or more cells.
• Cells are the basic units of structure and function in organisms.
• Cells arise from pre-existing cells through cell division.

Types of Microscopes

• Compound Microscope: Used to view cells and tissue sections, illuminating the object with sunlight or artificial light.
• Stereomicroscope: Examines the external structures of specimens, like insects.
• Phase-contrast Microscope: Useful for viewing highly transparent objects, such as unstained cells, offering a greater degree of detail.
• Electron Microscope: Uses streams of electrons to enlarge objects up to 10 million times. Subtypes exist:
  • Transmission Electron Microscope (TEM): examining internal structures of cells by sectioning specimens,
  • Scanning Electron Microscope (SEM): examining the 3D structure or shape of objects like viruses.
• Fluorescent Microscope: extensively used to study the location of certain organelles or substances within cells, using fluorescence labelling of structures.
• Confocal Scanning Microscope: Used to view three-dimensional structures of cells or organelles without sectioning the specimen.

Explore the origins of life and the development of cell theory in this quiz. Learn about the early protocells, the contributions of Robert Hooke and Anton van Leeuwenhoek, and the impact of their discoveries on our understanding of biology. Test your knowledge of foundational concepts in cellular biology.