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ESSENTIAL AMINO ACIDS |
NONESSENTIAL AMINO ACIDS |
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Tryptophan |
Alanine |
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Valine |
Proline |
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Threonine |
Tyrosine |
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Isoleucine |
Cysteine |
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Leucine |
Serine |
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Lysine |
Glutamine |
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Phenylalanine |
Glutamic acid |
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Methionine |
Glycine |
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Arginine* |
Asparagine |
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Histidine* |
Aspartic acid |
*essential during growth
What do proteins look like?
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As mentioned above, peptides and proteins are comprised of links of amino acids. Some smaller proteins will exist as a somewhat straight chain of amino acids; however, most proteins will exist in a complex three-dimensional design (see 3D Protein Figure). Links of amino acids will contort themselves based upon the specific sequencing of the amino acids. |
How links of amino acids contort depends on the interaction between the side groups “R” group on the different amino acids. For instance, some amino acids are attracted to other amino acids in the chain while others are repulsed. This is due to either opposing or similar charges. An analogy would be children holding hands to form a chain. As you can imagine, within a short period of time the chain would bend in a manner specific to the children. Some children would want to be closer (or further away) from others. As amino acid chain bends, twists, and warps about three dimensionally, some amino acids will form bonds with other amino acids. This helps stabilize the three-dimensional design.
It will be the final structure that determines the functional properties of a protein. It is interesting that many proteins are actually all globbed up, somewhat like crumpled paper or loosely packed yarn. In fact, the names of some proteins, such as hemoglobin and immunoglobin, reflect their globbed (globular) nature. On the contrary, many proteins have more of a filament design, meaning that they are much longer than they are wide. Many of these proteins are like stretched out coils. This is the case with collagen. In fact, numerous collagen proteins come together, side by side, to form a ropelike fibrous super-protein. Further still, it is possible for a protein to demonstrate both globular and filament attributes as is the case with muscle proteins actin and myosin.
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