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A protein is a chain of amino acids. An amino acid is a
___1___ molecule
that acts as the building block of any protein. Amino
acids provide cells with the building material they need
to grow and maintain their structure. Amino acids ___2___
called "amino acids" because they all contain an amino
group ( NH2 ) and a carboxyl group ( COOH ), which is
acidic. The human body is constructed of 20 different
amino acids. There are two different types of amino
acids : essential and non-essential. Non-essential amino
acids are amino acids that your body can create out of
other chemicals ___3___
in your body. Essential amino acids cannot be created,
and therefore the only way to get them is through food.
Protein in our diet comes from both animal and
vegetable sources. Most animal sources such as meat,
milk and eggs provide complete protein, meaning that
they contain all of the essential amino acids. Vegetable
sources usually are low or are missing certain essential
amino acids. For example, rice is low in isoleucine and
lysine. However, different vegetable sources are
deficient in different amino acids and ___4___
combining different foods you can get all of the
essential amino acids throughout the course of the day.
The digestive system breaks all proteins down into their
amino acids so that they can ___5___
the bloodstream. Cells then use the amino acids as
building blocks. |
