You will read in this book about experiments that revealed secrets of cell and molecular biology, many of which earned their researchers Nobel and other prizes. But let’s begin here with a Tale of Roberts, two among many giants of science in the renaissance and age of enlightenment whose seminal studies came too early to win a Nobel Prize.
One of these, Robert Boyle, was born in 1627 to wealthy, aristocrat parents. In his teens, after the customary Grand Tour of renaissance Europe (Greece, Italy…) and the death of his father, he returned to England in 1644, heir to great wealth. In the mid-1650s he moved from his estates to Oxford where he set about studying physics and chemistry. He built a laboratory with his own money in order to do experiments on the behavior of gasses under pressure, and with a little help, discovered Boyle’s Law, confirming that the gasses obey mathematical rules. He is also credited with showing that light and sound could travel through a vacuum, that something in air enables combustion, that sound travels through air in waves, that heat and particulate motion were related, and that the practice of alchemy was bogus! In fact, Boyle pretty much converted alchemy to chemistry by doing chemical analysis, a term he coined. As a chemist, he also rejected the old Greek concept of earth, air, fire and water elements. Instead, he defined elements as we still do today: the element is the smallest component of a substance that cannot be further chemically subdivided. He did this a century before Antoine Lavoisier listed and define the first elements! Based on his physical studies and chemical analysis, Boyle even believed that the indivisible unit of elements were atoms, and that the behavior of elements could be explained by the motion of atoms. Boyle later codified in print the scientific method that made him a successful experimental scientist.
The second of our renaissance Roberts was Robert Hooke, born in 1635. In contrast to Boyle parents, Hooke’s were of modest means. They managed nonetheless to nurture their son’s interest in things mechanical. While he never took the Grand Tour, he learned well and began studies of chemistry and astronomy at Christ Church College, Oxford in 1653. To earn a living, he took a position as Robert Boyle’s assistant. It was with Hooke’s assistance that Boyle did the experiments leading to the formulation of Boyle’s Law. While at Oxford, he made friends and useful connections. One friend was the architect Christopher Wren. In 1662, Boyle, a founding member of the Royal Society of London, supported Hooke to become the society’s curator of experiments. However, to support himself, Hooke hired on as professor of geometry at Gresham College (London). After “the great fire” of London in 1666, Hooke, as city surveyor and builder, participated with Christopher Wren in the design and reconstruction of the city. Always interested in things mechanical, he also studied the elastic property of springs. This led him to Hooke’s Law, which said that the force required to compress a spring was proportional to the length the spring was compressed. In later years these studies led Hooke to imagine how a coil spring might be used (instead of a pendulum) to regulate a clock. While he never invented such a clock, he was appointed to a Royal Commission to find the first reliable method to determine longitude at sea. He must have been gratified to know that the solution to accurate determination of longitude at sea turned out to involve a coil- spring clock! Along the way in his ‘practical’ studies, he also looked at little things, publishing his observations in Micrographia in 1665. Therein, he described microscopic structures of animal parts and even snowflakes. He also described fossils as having once been alive, and compared structures in thin slices of cork that he saw in his microscope to monk’s cells (rooms, chambers) in a monastery. Hooke is best remembered for his law of elasticity, and of course, for coining the word cell, which we now understand as the smallest unit of living things.
Now fast-forward almost 200 years to observations of plant and animal cells early in the 19th century. Many of these studies revealed common structural features including a nucleus, a boundary wall and a common organization of cells into groups to form multicellular structures of plants and animals and even lower life forms. These studies led to the first two precepts of Cell Theory:
(1) Cells are the basic unit of living things;
(2) Cells can have an independent existence.
Later in the century when Louis Pasteur disproved notions of spontaneous generation, and German histologists observed mitosis and meiosis (the underlying events of cell division in eukaryotes) a third precept rounded out Cell Theory: They reproduce.
(3) Cells come from pre-existing cells.
We begin this chapter with a reminder of the scientific method, that way of thinking about our world that emerged formally in the 17th century. Then we take a tour of the cell, reminding ourselves of basic structures and organelles. After the ‘tour’, we consider the origin of life from a common ancestral cell and the subsequent evolution of cellular complexity and the incredible diversity of life forms. Finally, we consider some of the methods we use to study cells. Since cells are small, several techniques of microscopy, cell dissection and functional/biochemical analysis are described to illustrate how we come to understand cell function.
When you have mastered the information in this chapter, you should be able to:
1. compare and contrast hypotheses and theories and place them and other elements of the scientific enterprise into their place in the cycle of the scientific method.
2. compare and contrast structures common to and that distinguish prokaryotes, eukaryotes and archaea, and groups within these domains.
3. articulate the function of different cellular substructures.
4. explain how prokaryotes and eukaryotes accomplish the same functions, i.e. have the same properties of life, even though prokaryotes lack most of the structures.
5. outline a procedure to study a specific cell organelle or other substructure.
6. describe how the different structures (particularly in eukaryotic cells) relate/interact with each other to accomplish specific functions.
7. describe some structural and functional features that distinguish prokaryotes (eubacteria), eukaryotes and archaea.
8. place cellular organelles and other substructures in their evolutionary context, i.e., describe their origins and the selective pressures that led to their evolution.
9. distinguish between the random nature of mutation and natural selection in evolution
10. relate archaea to other life forms and speculate on their origins in evolution.
11. suggest why evolution leads to more complex ways of sustaining life,
12. explain how fungi are more like animals than plants.