History – Introduction to Biochemistry

by Kevin Ahern, PhD

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    00:01 Now our perspective of life has changed considerably over the years. Dating back to the Renaissance, there was a considerable interest in understanding life by understanding anatomy. So dissections became very common, because people were interested in understanding what did it mean to be alive by understanding how did an organ or how did a tissue function. So one of the common beliefs that has been held by people over thousands of years has actually been the principle of vitalism. Vitalism states that what happens in a living cell is unique to a living cell and can't be duplicated elsewhere in the universe. That idea was basically proven to be false by the person shown on the screen, Friedrich Wöhler. Wöhler was able to show, using ordinary chemistry that he could make urea, a compound that was known to be made by living organisms, and prior to his discovery was believed only made to be possible by cells. Thanks to the discovery of vitalism, we now realize that what happens with cells is the same thing that happens in the rest of the universe, although perhaps in a different way.

    01:07 Now the discoveries of life and the molecular nature of life have been totally dependent upon technology. The first technological advance that had importance in helping us to understand cells was the invention of the microscope. Anton Van Leeuwenhoek in the 1650's invented the very first microscope and he was the first person ever to see single cell organisms, organisms that he called animalcules. He was very, very intrigued by these cells.

    01:35 Robert Hooke made some significant improvements on the Van Leeuwenhoek microscope and was able to make some very interesting discoveries, including something that we carry forward today which was the cell basis of life. His anatomical drawings of cork, as seen on the screen here, showed individual cells and reminded us that every living cell came from a previously living cell. By the 1850s, the discovery of the molecules that are important for the molecular basis of life came into being. Friedrich Miescher discovered a compound, working in the 1850s, that he called nucleon. Now he was interested in studying proteins but what he did was he isolated nuclei and when he isolated nuclei of cells, he discovered it contained a substance that had some very unusual properties. He didn't know what those properties were, but he knew he had discovered something new and important that he called nucleon. We know today of course the nucleon is DNA. The Augustine monk Gregor Mendel was interested and he was studying about at the same time as Miescher. Gregor Mendel was interested in studying the inheritance of traits from one generation of peas to another generation and he made very, very careful studies and in his studies realize that there was genetic information that was being transferred from one generation to the next. And further that that genetic information had properties that he called recessiveness and dominance, traits that we associate with genes. Mendel's work was largely undiscovered for about 30 years, but when it became to be discovered, it was revealed as quite a revolutionary finding, certainly for its time.

    03:15 By the 1930s, the idea of the molecular basis of life started to come to fruition.

    03:20 Erwin Schrödinger, the famous physicist, wrote a book called 'What is life?' and in his book he posed the question that the cell was not the most fundamental thing with respect to life. Instead he said that the molecular basis of life within molecules that the basis of life was in molecules. And within those molecules we can find every trait that would ever occur in biology. His idea was radical at the time, but in fact it had great influence over many people who later made giant discoveries including Watson and Crick in their discovery of DNA.

    03:56 We know today that Schrödinger was basically correct, that is, that life has a molecular basis. Avery, MacLeod and McCarty in 1944 did a series of experiments that proved definitively, for the first time, that the genetic information that was being transferred between generations of cells was in fact DNA. Only a few years later in 1953, Watson and Crick standing on the shoulders of giants and borrowing the data of Rosalind Franklin, were able to show for the first time the structure of DNA.

    04:31 The beautiful double helical molecule with a complementary basis inside was a revelation, because upon seeing it people quickly realized how one strand could specify the replication of another strand. And through that replication genetic information could be transferred identically from one cell to the next generation. The central dogma states that DNA makes RNA, makes protein and that happens because of the way information is transferred in cells.

    05:00 We've modified the central dogma since it was first described in the early 60's to incorporate some other things about RNA that we know today that we didn't know then. But the central dogma and its description of the transfer of information within cells is central to everything that we do. Whether we're studying genomics, whether we're studying transcriptomics or whether we're studying metabolomics, the central dogma is as relevant today as it was when it was first described.

    05:25 Now in concluding this talk, I want to leave you with some thoughts relevant to the structure of bacteria that I mentioned earlier, “Excuse me for feeling superia, to all of the lowly bacteria. You should know very well, there is no organelle, inside of their tiny interia”

    About the Lecture

    The lecture History – Introduction to Biochemistry by Kevin Ahern, PhD is from the course Biochemistry: Basics.

    Included Quiz Questions

    1. Antonie van Leeuwenhoek
    2. Zacharias Janssen
    3. Robert Hooke
    4. Gregor Mendel
    5. Galileo Galilei
    1. Erwin Schrödinger — micrographia
    2. Antonie van Leeuwenhoek — discovery of microbes
    3. Robert Hooke — coined term cell
    4. Gregor Mendel — father of modern genetics
    5. Friedrich Miescher — isolation of nucleic acid

    Author of lecture History – Introduction to Biochemistry

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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