00:02
The aromatic family is next stem we
will consider, the synthesis of.
00:06
These include the amino acids:
tryptophan, phenylalanine and tyrosine.
00:12
Each of these amino acids is derived
from some very simple precursors.
00:17
Phosphoenolpyruvate which is an
intermediate in the glycolysis pathway
and erythrose-4-phosphate
which is an intermediate
from the pentose phosphate,
phosphate pathway.
00:27
The synthesis
pathways are complex.
00:29
And again, I'm not going to
go into individual reactions
other than to show you the
schematic that we see here.
00:35
Each of the synthetic
pathways involves the
production of shikimic
acid and chorismic acid.
00:40
We can see the chorismate or the
chorismic acid in the schematic here.
00:44
Phenylalanine and tyrosine
pathways overlap because
tyrosine can be produced
directly from phenylalanine.
00:51
It can also be produced
independently of it as well.
00:55
Hormones and neurotransmitters are
made from each of these amino acids.
00:59
So this aromatic family has a lot of
connections to other things that cells need.
01:05
Now the synthesis of
tryptophan is interesting.
01:07
Its regulated synthesis
in bacteria has a very
interesting mechanism
known as attenuation.
01:14
Attenuation is a way of
controlling an entire operon.
01:17
Now an operon is a
set of five genes.
01:20
Making five genes takes
a lot of energy.
01:23
So cells only want to be
synthesizing those five genes
to make tryptophan when
tryptophan is itself needed.
01:29
If tryptophan is available,
making those genes waste energy.
01:34
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.
01:43
When tryptophan
concentration is high,
then the transcription of the operon to
make those five genes actually aborts.
01:50
It starts, but it aborts.
01:53
That prevents these five
genes from being made and
saves energy because
tryptophan is available.
01:59
When tryptophan supply is slow, that
aborted process does not occur.
02:04
The entire transcription of
the entire operon occurs.
02:07
So this process is attenuation.
02:09
Very interesting way of controlling
synthesis of a set of genes.
02:15
The molecules made from tryptophan
are shown in the screen here.
02:18
They include melatonin.
02:19
And melatonin is important for
circadian rhythm sensing.
02:24
It affects our mood, it affects our
sleep, affects our blood pressure.
02:28
Melatonin is used in some
sleeping treatments actually.
02:33
The production of melatonin, we know
now, is affected by blue light.
02:38
And the more blue light we have,
especially later in the evening,
the less melatonin we produce.
02:44
The less melatonin we produce, the
more sleeping difficulty we have.
02:48
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.
03:00
Serotonin is what people refer
to as the happy hormone.
03:03
It's a neurotransmitter.
03:04
It causes vasoconstriction, which
actually increases blood pressure,
and then enhances memory, learning and
it's a contributor to happy feelings.
03:13
When you're feeling well, feeling happy,
you're probably producing serotonin.
03:19
Niacin we can see is
one of our vitamins.
03:21
It's known as vitamin B3.
03:24
It's important component
of nicotinamide.
03:27
And nicotinamide is used to make
NAD, NADH, NADP, and NADPH.
03:33
A deficiency of vitamin
B3 is very severe
and leads to the disease
known as an pellagra.
03:40
The last of the molecules made from
tryptophan is that the auxins.
03:43
There are families of
molecules and indole-3-acetic
acid is the most important
and the most common one.
03:49
It is a plant hormone and was in fact the
first plant hormone that was discovered.
03:54
It's used in plants to stimulate cell
division and causes rooting in the plants.