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Endocrinology - Overview

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    ARMANDO HASUDUNGAN:
    Armando Hasudungan Biology
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    Armando Hasudungan.
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    Now, in this video, we will look
    at an overview of transcription
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    and translation in cells.
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    It won't go into a
    whole lot of detail,
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    but just so we get an
    idea of what is happening.
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    So we begin by
    going inside a cell.
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    Here is the membrane of
    the nucleus, not the plasma
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    membrane but the nucleus, where
    our genetic material is stored.
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    And outside this
    nuclear membrane
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    is the cytoplasm, which is
    the fluid within the cell.
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    Now, within the cytoplasm,
    we find many things,
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    including amino acids.
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    And there are many
    types of amino acids.
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    There are 20 in total.
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    Now, going back
    inside the nucleus,
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    we can find our
    genetic material,
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    which are packaged
    up into chromosomes,
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    forming chromosomes.
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    We have 46 chromosomes in total,
    23 pairs, one from each parent.
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    If we unpack this
    particular chromosome,
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    the genetic material is cleverly
    wrapped around these proteins
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    called histones.
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    So pulling out some
    of these histones,
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    our genetic material
    here are organized,
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    wrapped around these
    individual histones.
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    Our genetic material is
    called DNA, or, long,
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    deoxyribonucleic acid.
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    If we unwind the DNA, we can see
    that the DNA is double stranded
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    and is made up of nucleotides.
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    There are four
    types of nucleotides
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    which make up the DNA.
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    So what do we do with this DNA?
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    Well, we can replicate
    it, and we do so
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    during cell division
    called mitosis.
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    And I have a video on that if
    you want to watch it, here.
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    Our DNA also
    contains many genes.
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    Genes are regions in the DNA
    that do things for our body.
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    For example, genes
    make templates
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    for proteins and enzymes.
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    To make proteins and
    enzymes for our body,
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    first, the DNA has to make RNA.
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    RNA stands for ribonucleic acid.
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    Our body makes RNA through the
    help of an enzyme called RNA
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    polymerase.
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    Now, RNA polymerase
    synthesizes an RNA
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    using one of the DNA
    strands as a template.
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    This process of
    synthesizing RNA from DNA
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    is called transcription
    because we are transcribing.
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    RNA typically has a
    poly-A tail, which
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    means it has many adenosine
    nucleotide at one end.
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    And on the other
    end, there is a cap,
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    and we'll talk about
    these features later on.
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    This particular RNA
    that was synthesized
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    by the RNA polymerase
    is a messenger RNA,
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    or mRNA for short.
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    It is a pre-mRNA,
    to be specific,
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    because it has not been
    properly converted to a mRNA.
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    There are actually three
    major types of RNA in humans.
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    These are the messenger RNA,
    mRNA, transfer RNA, tRNA,
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    and ribosome RNA, rRNA.
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    And they are all synthesized
    by different types
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    of RNA polymerases.
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    You have RNA polymerase
    I, II, and III.
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    But we don't have to
    worry about that now.
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    Anyways, let's go back to the
    pre-mRNA that was just made.
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    So now we are focusing
    on messenger RNA.
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    The pre-messenger RNA,
    like all pre-RNAs,
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    are made up of
    nucleotides as well.
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    They also contain regions
    called introns and exons.
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    The pre-mRNA then undergoes
    a process known as splicing.
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    Splicing is basically when
    the regions, called introns,
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    are removed from the pre-mRNA.
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    But the exons, they will stay.
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    And this will form a
    unique type of mRNA
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    and therefore a unique
    type of protein.
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    So after splicing, after
    introns are removed,
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    this will form an mRNA,
    still with the poly-A tail
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    at one end and a
    cap at the other.
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    Now, the mRNA will
    then leave the nucleus
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    through the nuclear pore
    and into the cell cytoplasm.
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    So we know that the
    mRNA has something
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    to do with making proteins.
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    What does it actually do?
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    Well, the mRNA serves as a
    template to form proteins.
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    mRNA is sort of
    like a foreign book
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    that has to be translated
    to make proteins,
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    if that made any sense.
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    Now, let's just pause there
    with the mRNA and look
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    at the other RNAs
    because they are
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    they are important
    as they participate
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    in protein synthesis.
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    So let's go back to the
    nucleus, to the DNA again.
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    A specific type
    of RNA polymerase
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    can synthesize pre-tRNA,
    pre-transfer RNA,
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    through the process
    called transcription.
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    The pre-tRNA is then spliced,
    removing the introns,
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    and then you get a type of tRNA.
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    The tRNA will then leave the
    nucleus to the nuclear pore
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    into the cytoplasm.
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    The tRNA will actually
    fold up into a shape
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    that looks sort of like this.
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    So what do we do
    with these tRNAs?
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    Or what do the tRNAs do?
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    Well, remember that tRNA is
    made up of nucleotides, not
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    amino acids.
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    And what tRNA actually do
    is that every tRNA will
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    attach to one amino acid.
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    Remember, in the cytoplasm,
    there are amino acids.
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    See, in the cytoplasm,
    there is this enzyme called
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    aminoacyl tRNA synthetase.
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    Aminoacyl tRNA
    synthetase essentially
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    attaches an amino
    acid to a tRNA,
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    forming a tRNA
    with an amino acid.
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    So now what we have
    in the cytoplasm
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    is tRNA with different
    types of amino acids.
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    Then we have an mRNA, which
    is a template for the tRNA
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    with the amino acid.
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    So what is missing?
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    Well, the only thing
    that is missing
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    is an enzyme that
    actually connects the two,
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    connects the tRNA with the mRNA.
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    This enzyme is
    called a ribosome,
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    and a ribosome is made from
    rRNA, our last type of RNA.
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    So let's go back to
    the nucleus and see
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    how we form this ribosome.
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    But before that, please remember
    that all these RNA, tRNA, mRNA,
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    they are all RNAs.
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    They are all made up of
    nucleotides, not amino acids.
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    So we are back in the
    nucleus to form ribosomes.
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    We actually have to dig
    deeper into the nucleus,
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    a region called the nucleolus.
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    Our DNA in the nucleolus
    have genes to make ribosomes.
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    A special RNA polymerase
    called RNA polymerase
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    I will synthesize
    rRNA, ribosome RNA.
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    And if I have not
    mentioned earlier,
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    the RNA polymerase
    that synthesizes tRNA
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    is RNA polymerase III.
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    Anyways, let's go
    back to the nucleolus.
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    RNA polymerase I will synthesize
    pre-rRNA, pre-ribosome RNA,
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    which will be spliced to
    form two rRNA strands.
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    One is small, and
    the other one is big.
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    The small and the
    big rRNA strands
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    will eventually form the
    small and large subunit
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    of the ribosome.
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    These strands will then
    leave the nucleolus,
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    where they will fold to form
    a small and large subunit
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    of the ribosome.
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    The subunits are still termed
    pre-ribosome in the nucleus.
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    The pre-ribosome can then leave
    the nucleus into the cytoplasm.
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    Within the cytoplasm, the
    small and large subunit
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    will attach to the cap
    end of the mRNA, like so.
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    So here we have a
    functioning ribosome
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    with its large and
    small subunit attaching
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    to the cap region of the mRNA.
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    The ribosome has
    three special sites
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    within it, the E, P, A site.
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    Now, each of these
    mean something.
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    But just for simplicity,
    you can think
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    of A as attachment, E as exit.
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    So anyways, the ribosome will
    move towards the poly-end
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    of the mRNA like so.
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    During its movement,
    the ribosome
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    will act like a factory
    for protein synthesis.
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    It will attach tRNA
    with mRNA, essentially.
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    Remember, the tRNA is
    made up of nucleotides,
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    so all these are nucleotides.
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    Three nucleotides down
    this end of the tRNA
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    is special because it is
    what will bind to three
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    nucleotides on the mRNA.
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    These three nucleotides
    are called codons
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    in mRNA and anticodons in tRNA.
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    So, for example, if
    this tRNA anticodon
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    matches this codon
    of the mRNA, it
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    will bind on the A
    site of the ribosome.
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    The ribosome will
    then keep moving,
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    and then the tRNA will then be
    on the P site of the ribosome.
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    The ribosome will
    release the amino acid
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    from the tRNA in the P site.
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    And then as the
    ribosome keeps moving,
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    the tRNA then will exit
    through the E site.
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    The amino acid that was
    released from the tRNA
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    will join with other amino
    acids from other tRNAs
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    to form a polypeptide
    or protein.
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    Now, this whole process
    is known as translation.
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    So what the ribosomes
    are doing is
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    that the ribosomes are
    translating the mRNA
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    to make proteins.
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    Now, just for your
    interest, this protein
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    that is just synthesized by the
    ribosome or any other proteins
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    for that matter can be broken
    down into amino acids again,
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    and then the cycle can continue.
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    What is important
    to understand here
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    is that amino acids,
    tRNA, mRNA, and rRNA
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    are critical in
    synthesizing proteins.
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    Also, many enzymes in our
    body are made up of proteins.
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    They're proteins.
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    However, a ribosome is not
    made up of amino acids.
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    It is made up of nucleotides.
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    Quite unique.
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    Thank you for watching.
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    Hope you enjoyed
    this short overview
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    on translation
    and transcription.
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    Bye.
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Title:
Endocrinology - Overview
Description:

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Video Language:
English
Duration:
21:16
steven.yi edited English subtitles for Endocrinology - Overview Jan 31, 2025, 7:08 AM
steven.yi edited English subtitles for Endocrinology - Overview Jan 31, 2025, 7:06 AM

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