BIO 205 — Introductory Developmental / Cell Biology: Lecture Note

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BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: BIO 205 Course title: Introductory Developmental / Cell Biology Course credit load: 2 Units Series 1: History and Trends in Cell Biology • Part 1.1: Early History of Cell Biology o Sub Part 1.1.1: Pre-microscopic understanding of life o Sub Part 1.1.2: The invention of the microscope and early cell observations o Sub Part 1.1.3: Formulation of the cell theory • Part 1.2: Development of Microscopy and Cell Study Techniques o Sub Part 1.2.1: Light microscopy and histological methods o Sub Part 1.2.2: Electron microscopy and ultrastructural studies o Sub Part 1.2.3: Cell fractionation and biochemical approaches • Part 1.3: Milestones in Molecular and Cellular Biology o Sub Part 1.3.1: Discovery of DNA structure and the molecular revolution o Sub Part 1.3.2: Development of cell culture and cloning technologies o Sub Part 1.3.3: Genomics, proteomics, and systems biology • Part 1.4: Current Trends and Frontiers in Cell Biology o Sub Part 1.4.1: Live-cell imaging and super-resolution microscopy o Sub Part 1.4.2: Cell signalling and systems approaches o Sub Part 1.4.3: Stem cells, synthetic biology, and medical applications

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Introduction Cell biology is the branch of biology that studies the structure, function, and behaviour of cells, the fundamental units of life. All living organisms, from the simplest bacteria to the most complex multicellular plants and animals, are composed of cells; understanding the cell is therefore central to understanding all of biology. The history of cell biology is closely tied to the development of technologies that allow scientists to visualise and manipulate cells and their components, from the first primitive light microscopes of the seventeenth century to the cryo-electron microscopes and super-resolution fluorescence systems of the twenty-first century. This Series traces the intellectual and technological history of cell biology from pre-scientific ideas about the organisation of living matter through the formulation of the cell theory in the nineteenth century, the ultrastructural revolution brought about by electron microscopy in the twentieth century, and the molecular revolution that followed the discovery of the DNA double helix; it concludes with a survey of current frontiers, including live-cell imaging, cell signalling networks, stem cell biology, and synthetic biology. This historical context is essential for understanding why modern cell biology is structured the way it is and how today’s experimental tools were developed. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 describe the pre-microscopic understanding of life, explain the key observations made with early microscopes, and state the three tenets of the cell theory (Linked to Part 1.1), • SLO 1.2 describe the development of light microscopy, electron microscopy, and cell fractionation as tools for studying cells, and explain what each technique revealed about cell structure (Linked to Part 1.2), • SLO 1.3 describe the key milestones of the molecular revolution in cell biology, from the discovery of DNA structure to the development of genomics and proteomics (Linked to Part 1.3), and

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS • SLO 1.4 describe current frontiers in cell biology, including super-resolution microscopy, cell signalling, stem cell research, and synthetic biology, and their medical applications (Linked to Part 1.4). 1.1 Early History of Cell Biology 1.1.1 Pre-microscopic understanding of life Before the invention of the microscope, ancient Greek, Roman, and Arab scholars speculated extensively about the organisation and composition of living matter, but without the tools to observe cells directly, their ideas remained largely philosophical. Aristotle (384 to 322 BC) proposed that the body was composed of four humours (blood, phlegm, yellow bile, and black bile) and that living matter was organised into hierarchical levels (organs, tissues), but he had no concept of the cell as the fundamental structural unit. Galen (129 to 216 AD) extended Aristotelian anatomy through animal dissection and recognised that different tissues had different textures and compositions, but again without knowledge of cellular organisation. Islamic scholar Ibn Sina (Avicenna, 980 to 1037 AD) produced encyclopaedic works on medicine and natural history but similarly lacked the technology to observe cells. The dominant pre-microscopic view was that living matter was fundamentally different from non-living matter (vitalism) and was organised as a continuum of tissue types rather than as discrete structural units. The concept of spontaneous generation also pervaded pre-microscopic biology: many philosophers and naturalists believed that living organisms could arise spontaneously from non-living matter (maggots from meat; mice from grain; algae from muddy water). This idea persisted until Francesco Redi (1668) demonstrated experimentally that maggots did not arise on meat protected from flies, and was finally disproved for microorganisms by Louis Pasteur’s swan-neck flask experiments (1859 to 1861). The eventual refutation of spontaneous generation was closely tied to microscopic observations of microorganisms and laid intellectual groundwork for the germ theory of disease and the understanding that all cells come from pre-existing cells (the third tenet of cell theory).

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: Before the microscope, the dominant view of living matter was ________ (the idea that life is fundamentally different from non-living matter and cannot be reduced to simple physical components); the pre-microscopic era lacked the technology to observe cells but generated important anatomical knowledge through dissection and philosophical reasoning. 1.1.2 The invention of the microscope and early cell observations The invention of the compound microscope in the late sixteenth century opened the first window into the microscopic world. The earliest microscopes are attributed to Dutch spectacle makers, including Hans Janssen and his son Zacharias Janssen (around 1590), who combined two lenses in a tube to produce a magnified image. Galileo Galilei also constructed a compound microscope around 1624. However, the first major biological discoveries using the microscope are credited to Robert Hooke (1635 to 1703), an English natural philosopher, who published his observations in Micrographia (1665). Hooke examined thin slices of cork under his compound microscope and observed that the cork was divided into tiny box-like compartments, which he named cells (from the Latin cella, meaning a small room), because they reminded him of the cells of a monastery. Hooke’s cells were in fact the empty cell walls of dead plant cells, as cork is composed of dead cells whose cytoplasmic contents have long since disappeared. The Dutch draper and self-taught microscopist Antonie van Leeuwenhoek (1632 to 1723) made even more remarkable observations. Leeuwenhoek constructed single-lens microscopes of exceptional quality (magnifying up to approximately 270×), far superior to the compound microscopes of his day. Using these instruments, he was the first to observe and describe bacteria (which he called animalcules) in dental scrapings and pond water (1674 to 1683), protozoa, red blood cells, spermatozoa, and the capillary circulation of blood in the tail of a fish. His observations, communicated to the Royal Society of London in a series of letters, established that a rich microscopic world of living organisms existed that was completely invisible to the naked eye. Subsequent microscopists of the seventeenth and eighteenth centuries, including Marcello Malpighi (1628 to 1694; first to describe capillaries in frog lungs, 1661) and Nehemiah Grew (1641 to 1712; described plant cell walls and pores), extended microscopic knowledge of tissues and cells, though the overarching framework of cell theory had not yet been formulated.

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: Robert Hooke named the small box-like compartments he observed in cork ________ (from the Latin for small room) in his 1665 publication Micrographia; Antonie van Leeuwenhoek was the first to observe bacteria, protozoa, and spermatozoa using single-lens microscopes of his own construction. 1.1.3 Formulation of the cell theory The cell theory, one of the great unifying principles of biology, was formulated in the mid-nineteenth century through the work of Matthias Schleiden, Theodor Schwann, and Rudolf Virchow. Matthias Schleiden (1804 to 1881), a German botanist, concluded in 1838 that all plant tissues are composed of cells and that the cell is the basic unit of plant structure. Theodor Schwann (1810 to 1882), a German zoologist and Schleiden’s colleague, extended this conclusion to animal tissues in 1839, proposing that all animals are also made of cells and that the cell is the elementary unit of life. Together, Schleiden and Schwann formulated the first two tenets of the cell theory: (1) All living organisms are composed of one or more cells; (2) The cell is the basic unit of structure and function in all living organisms. Rudolf Virchow (1821 to 1902), a German physician and pathologist, added the third and crucial tenet in 1855: (3) All cells arise from pre-existing cells (Omnis cellula e cellula), rejecting spontaneous generation and establishing that life is a continuous process of cell division from existing cells. The cell theory transformed biology by providing a unifying structural framework: just as

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