What determines the quality of protein in food. Quality of protein is not about the amount of protein in a food and is not related to other nutrients in the food, such …
Students frequently have problems
understand the concept of quality of protein
so this video is to help you visualize
what this means.
As you know, when we eat foods, our foods are going to be digested.
We are going to eat it and we are going to end up, we are going to unfold it in the stomach.
And we will end up with those end products of digestion in the small intestines to the single amino acids.
Then these amino acids will be
absorbed and put into that amino acid pool.
Absorption. I want to remind you that there is no specific place in the body
that has an amino acid pool. It is just
a way to visualize it, to think about these
single amino acids and that the body
will use these amino acids to actually
pull from to produce a protein. So, we're
going to pull from that, whether it's
from a blood or from a cell itself, we'll
pull from this pool of amino acids to
create a body protein And so, this is
going to be our goal protein and with
this example I've been using letters to
represent amino acids. Though we know
that the sequence of amino acids is
going to be important. We have got to have
the sequence, determined by the
DNA, to give us our structure of
protein that we need eventually.
With this example, I am using some
color coding here.
If the letter is gray, we are going to say it is a non-essential amino acids.
If a letter has a color to it, we will say that it is an essential amino acid.
and how that makes a difference when it comes to what happens
when you don't have enough of one or the other.
If we're going to build this sequence
of amino acids, we have to come from our pool.
We can see that we have the letter C.. so
we'll just make a mark…, but we don't have
we have one letter G…will make a mark by that G and say yeah we've got that.
We have got plenty of letter E's.
So, we're going to mark our letter E's. We've got letter S's. We only had the one letter G, so we now
have a problem. We do not have another letter G. We have plenty of letter T's and we're going to see
we've got the rest of these letters. We are doing fine.
We have a letter C's. We don't have a letter P.
If we look at our pool amino
acids, there's not a letter P, but we do have
plenty of letter S's and again we know we have run out of our G's.
So, now we have a situation where we
don't have all the amino acids needed
produce our protein.
You must have all amino acids before you
can produce a protein.
If it is a non-essential amino acid, it is no problem.
We can convert… If a non-essential amino acid is missing,
we'll just convert, one non-essential amino acid to another non-essential amino acid.
So, we can just take an extra "T" for an
example and will convert that to a "P."
There will be no problem. We can
continue to produce our protein because
we can actually get our "P" from another
non-essential amino acid.
But let's take a look at what happens if there isn't enough essential amino acids.
We know here that there's inadequate, in this example, there is inadequate "G's."
And with that "G," it is an essential
amino acid. (It is a colored letter in this example.)
We cannot produce, because by definition essential means we must eat it.
In this instance, we will actually stop protein production.
That can lead to problems. It can lead to lack of health. We can't produce our immune antibodies.
We can't produce growth because we can't grow enough tissue.
So that amount of essential amino acids in the original food… we come back to the original food.
We have to look at the types of amino acids that are in there because that is going to be what gives
us the pool of amino acids to pull from
to make our protein. So, we can come back to,
how do we measure the quality of a
protein? Protein quality is the measure of
how well the protein in a food provides
those essential amino acids to meet
protein production needs. If we don't have enough essential amino acids our
protein production will be limited or
stopped. So, non-essential amino acid
no problem, but essential amino acid
we will have a health problems or just
won't be able to produce enough of
the protein to maintain body structure.