BIOB10H3 Lecture Notes - Vacuole, Cell Theory, Archaea
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an instrument that provides a magniﬁed image of a tiny object. Cells are observed through it.
Discovery of cells:
Hooke called the pores cells because they reminded him of the cells inhabited by monks living in a
Anton van Leeuwenhoek
a Dutchman who earned a living selling clothes and buttons, was spending his spare time grinding lenses
and constructing simple microscopes of remarkable quality
Leeuwenhoek was the ﬁrst to examine a drop of pond water under the microscope and, to his amazement,
observe the teeming microscopic “animalcules” that darted back and forth before his eyes. He was also
the ﬁrst to describe various forms of bacteria, which he obtained from water in which pepper had been
soaked and from scrapings of his teeth. His initial letters to the Royal Society describing this previously
unseen world were met with such skepticism that the society dispatched its curator, Robert Hooke, to
conﬁrm the observations.
Theodor Schwann, a German zoologist and colleague of Schleiden’s, published a comprehensive report
on the cellular basis of animal life. Schwann concluded that the cells of plants and animals are similar
structures and proposed these two tenets of the cell theory:
¦ All organisms are composed of one or more cells.
¦ The cell is the structural unit of life.
By 1855, Rudolf Virchow, a German pathologist, had made a convincing
Case for the third tenet of the cell theory:
¦ Cells can arise only by division from a preexisting cell.
The ﬁrst culture of human cells was begun by George and Martha Gey of Johns Hopkins University in
1951. The cells were obtained from a malignant tumor and named HeLa cells after the donor, Henrietta
Lacks. HeLa cells—descended by cell division from this ﬁrst cell sample—are still being grown in the
Organisms are built according to information encoded in a collection of genes. The human genetic
program contains enough information, if converted to words, to ﬁll millions of pages of text. Remarkably,
this vast amount of information is packaged into a set of chromosomes that occupies the space of a cell
Genes are more than storage lockers for information: they constitute the blueprints for constructing
cellular structures, the directions for running cellular activities, and the program for making more of
themselves. The molecular structure of genes allows for changes in genetic information (mutations)
that lead to variation among individuals, which forms the basis of biological evolution