how many different amino acids are there

There are 20 standard amino acids used to build proteins in your body.

Quick Scoop: How many amino acids are there?

If someone asks in a biology or biochemistry context, “how many different amino acids are there?”, they usually mean:

• 20 standard (protein-building) amino acids encoded directly by the genetic code.

• These 20 are the basic “alphabet” that make up almost all proteins in humans and most life on Earth.

However, you’ll also see slightly different numbers in more detailed discussions:

• 21 proteinogenic amino acids if you include selenocysteine , which is built into certain special proteins using a modified translation mechanism.

• Hundreds in nature overall – roughly 500 different amino-acid-like molecules have been identified in nature, but most are not used directly to build standard proteins.

So for a straightforward answer:

For standard protein building in humans, there are 20 different amino acids, with a 21st special one (selenocysteine) sometimes counted separately.

Mini breakdown: types of those amino acids

Among the 20 standard amino acids in human proteins:

• 9 are essential (you must get them from food).

• The rest are nonessential or conditional , which your body can usually make on its own.

Some examples of essential amino acids include histidine, leucine, lysine, and tryptophan.

HTML table: key counts

html

<table>
  <thead>
    <tr>
      <th>Category</th>
      <th>Number</th>
      <th>What it means</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Standard protein-building amino acids</td>
      <td>20</td>
      <td>Encoded by the genetic code and used to build most proteins in humans and other organisms. [web:5][web:7]</td>
    </tr>
    <tr>
      <td>Proteinogenic amino acids including selenocysteine</td>
      <td>21</td>
      <td>Same 20 plus selenocysteine, a special case inserted into some proteins via a modified mechanism. [web:1][web:10]</td>
    </tr>
    <tr>
      <td>Essential amino acids (within the 20)</td>
      <td>9</td>
      <td>Cannot be synthesized by the body; must come from diet. [web:7][web:9]</td>
    </tr>
    <tr>
      <td>Different amino-acid-like molecules found in nature</td>
      <td>≈500</td>
      <td>Many exist in nature, but only a small subset (20–21) are used directly to build standard proteins. [web:5][web:6]</td>
    </tr>
  </tbody>
</table>

Forum-style note

On many biology forums, people will say “20” for simplicity, then add “plus selenocysteine makes 21” if they want to be precise. The much larger “about 500” refers to all amino-acid-type molecules known in nature, not just the ones in your DNA’s standard toolkit.

TL;DR: In everyday biology talk, there are 20 different standard amino acids, with a special 21st (selenocysteine) sometimes included for extra accuracy.

Information gathered from public forums or data available on the internet and portrayed here.