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Aromatic Family: Tryptophan

by Kevin Ahern, PhD
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    The aromatic family is next stem we will consider, the synthesis of. These include the amino acids: tryptophan, phenylalanine and tyrosine. Each of these amino acids is derived from some very simple precursors. Phosphoenolpyruvate which is an intermediate in the glycolysis pathway and erythrose-4-phosphate which is an intermediate from the pentose phosphate, phosphate pathway. The synthesis pathways are complex. And again, I'm not going to go into individual reactions other than to show you the schematic that we see here. Each of the synthetic pathways involves the production of shikimic acid and chorismic acid. We can see the chorismate or the chorismic acid in the schematic here. Phenylalanine and tyrosine pathways overlap because tyrosine can be produced directly from phenylalanine. It can also be produced independently of it as well. Hormones and neurotransmitters are made from each of these amino acids. So this aromatic family has a lot of connections to other things that cells need. Now the synthesis of tryptophan is interesting. Its regulated synthesis and bacteria has a very interesting mechanism known as attenuation. Attenuation is a way of controlling an entire operon. Now an operon is a set of five genes. Making five genes takes a lot of energy. So cells only want to be synthesizing those five genes to make tryptophan when tryptophan is itself needed. If tryptophan is available, making those genes waste energy. So they have involved a way of controlling whether or not those five genes are made or not made depending upon whether tryptophan is present or not present. When tryptophan concentration is high, then the transcription of the operon to make those five genes actually aborts. It starts, but it aborts. That prevents these five genes from being made and saves energy because tryptophan is available. When tryptophan supply is slow,...

    About the Lecture

    The lecture Aromatic Family: Tryptophan by Kevin Ahern, PhD is from the course Amino Acid Metabolism.


    Included Quiz Questions

    1. ...is synthesized from phosphoenolpyruvate (PEP) and erythrose-4-phosphate.
    2. ...includes phenylalanine, tyrosine, and histidine.
    3. ...is made primarily from neurotransmitters.
    4. All of the answers are true.
    5. None of the answers are true.
    1. All of the answers are correct.
    2. It is partly regulated by attenuation in bacteria.
    3. It is a precursor of plant hormones.
    4. It is a precursor of a vitamin.
    5. None of the answers are true.

    Author of lecture Aromatic Family: Tryptophan

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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