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
which is an intermediate
from the pentose phosphate,
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
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.
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, that
aborted process does not occur.
The entire transcription of
the entire operon occurs.
So this process is attenuation.
Very interesting way of controlling
synthesis of a set of genes.
The molecules made from tryptophan
are shown in the screen here.
They include melatonin.
And melatonin is important for
circadian rhythm sensing.
It affects our mood, it affects our
sleep, affects our blood pressure.
Melatonin is used in some
sleeping treatments actually.
The production of melatonin, we know
now, is affected by blue light.
And the more blue light we have,
especially later in the evening,
the less melatonin we produce.
The less melatonin we produce, the
more sleeping difficulty we have.
So one suggestion people have is not to use
your computer monitor too much at night
or to use a computer program
that actually reduces the
amount of blue light being
produced by your computer screen.
Serotonin is what people refer
to as the happy hormone.
It's a neurotransmitter.
It causes vasoconstriction, which
actually increases blood pressure,
and then enhances memory, learning and
it's a contributor to happy feelings.
When you're feeling well, feeling happy,
you're probably producing serotonin.
Niacin we can see is
one of our vitamins.
It's known as vitamin B3.
It's important component
And nicotinamide is used to make
NAD, NADH, NADP, and NADPH.
A deficiency of vitamin
B3 is very severe
and leads to the disease
known as an pellagra.
The last of the molecules made from
tryptophan is that the auxins.
There are families of
molecules and indole-3-acetic
acid is the most important
and the most common one.
It is a plant hormone and was in fact the
first plant hormone that was discovered.
It's used in plants to stimulate cell
division and causes rooting in the plants.