Overview – Introduction to Biochemistry

by Kevin Ahern, PhD

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    00:02 Increasing scientific knowledge and improved technology has played significant roles in helping us to better understand the molecular basis of life. In this lecture I will go through a brief overview of the summary of our understanding and our perspective of living system, from ancient times up until today. Life is abundant on planet Earth and as far as we know in the universe that's the only place it exists, although likely it exists in other places as well. Life is diverse and life is widespread. From the deserts in Africa to the farmlands of America. Life has found niches in every land system on earth. In the sea we can look in the deep sea thermal vents, we can look in the top of the ocean and everywhere we look, we see aquatic life. In the air we see birds, we see insects, we see microbes that are floating around. Every available ecosystem on earth that we've examined is abundant with life.

    01:02 Now human beings are people who organize and categorize things, and it's only natural therefore that we should be categorizing life systems as well. And one of the things that has happened in the organization of life systems is to create a hierarchical scheme. On the screen you can see one hierarchical scheme that is used to describe essentially every living organism on earth. Starting at the top with the most broad view and narrowing down as we go down through the names, domains of course relate to the very, very broad regions, relating to living systems. Kingdoms are a subdivision of that and phylum are a subdivision of the kingdoms, followed by class, order, family, genus and species. Now it's important to recognize that every life form on earth can be described by this hierarchical system.

    01:54 Another system for organizing life is that's shown the screen based on evolutionary distance.

    01:59 We think that all life on earth ultimately came from one primordial cell, and that one primordial cell evolved and gave rise to all the life forms that we see today. This plot shows as lines the evolutionary distance each living system is from that primordial cell and by extension how far each living system is evolutionarily from each of the other systems on the screen. On the lower left we can see bacteria. Bacteria of course are the single celled organisms that contain no organelles, they are very simple in their structure and they are very tiny. One of the ways people view bacterias as a bag of enzymes and nucleic acid and that's about what we find in bacteria. The archaeans are the more recently described types of life and they actually exist in some of the most inhospitable places on the planet.

    02:53 Environments that other cells would find toxic, the archaeans find home. Like bacteria, they're very simple as well. The eukarya shown on the right include the multicellular organisms we see on eart. This includes the animals, the fungi, the plants and many other multicellular and a few unicellular forms as well. One unicellular form we see in the eukaryotes includes the yeast, makers of bread and ethanol. Now the eukaryotic cells differ from the prokaryotic cells and the archaeon cells in first of all generally being considerably larger than them and second of all, in containing specialized organelles, like the nucleus and like the mitochondrion. These specialized organelles play distinct functions in these cells that are distributed otherwise throughout the entire bacterial or archaean cell.

    About the Lecture

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

    Included Quiz Questions

    1. Species
    2. Kingdom
    3. Family
    4. Domain
    5. Genus
    1. Yeast
    2. Fungi
    3. Bacterium
    4. Archaeon
    5. Virus

    Author of lecture Overview – Introduction to Biochemistry

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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