<h2>Molecules for Life</h2>
<p class="para">Although life at the macro level is diverse, the chemistry making up that life is remarkably similar. All living things are made up of basic building blocks called <em class="emphasis">elements</em>. An element is a substance that cannot be broken down into simpler substances using chemical means. Carbon, oxygen, hydrogen, nitrogen, sulfur, calcium, <a data-lesson="mineralocorticoids" data-subject="biology" data-tutorial="excretory-system" href="https://app.ulearngo.com/biology/excretory-system/mineralocorticoids">sodium</a> and iron are examples of elements you will come across in Life Sciences.</p>
<p class="para">Each element is distinguished by the composition of its <em class="emphasis">atom</em>. An atom is the basic unit of matter. <em class="emphasis">Molecules</em> are formed when one or more atoms are covalently bonded together. The atoms of a molecule can be identical, such as \(\text{O}_2\) or \(\text{H}_2\) or differ such as \(\text{H}_2\text{O}\). A <em class="emphasis">compound</em> is formed when atoms of <i class="emphasis">different</i> elements join together.</p>
<div class="ns-tutorial">
<div class="ns-school-defn2">
<h3 class="note-header"><span class="cnx_label">Interesting Fact:</span></h3>
<p class="para">Because all compounds contain more than one atom, all compounds are molecules. However, not all <a data-lesson="first-organic-molecules" data-subject="biology" data-tutorial="evolution-overview" href="https://app.ulearngo.com/biology/evolution-overview/first-organic-molecules">molecules</a> are compounds.</p>
</div>
</div>
<p>Compounds are divided into <em class="emphasis">organic</em> and <em class="emphasis">inorganic</em> compounds. Organic compounds always contain carbon, but not all compounds that contain carbon are organic. A general rule of thumb is that organic compounds contain carbon, with at least one of these carbons bonded to hydrogen atoms. Carbon dioxide is therefore an inorganic compound even though it contains carbon. The major organic compounds found in living organisms include: <em class="emphasis">carbohydrates</em>, <em class="emphasis">fats</em>, <em class="emphasis">proteins</em> and <em class="emphasis">nucleic acids</em>. These will be discussed in detail in the next couple of lessons.</p>
<table>
<tbody>
<tr>
<td>
<h3 class="para">Substance</h3>
</td>
<td>
<h3 class="para">Percentage</h3>
</td>
</tr>
<tr>
<td colspan="2"><strong>Inorganic</strong></td>
</tr>
<tr>
<td>
<p class="para">Water</p>
</td>
<td>
<p class="para">65%</p>
</td>
</tr>
<tr>
<td>
<p class="para">Mineral salts</p>
</td>
<td>
<p class="para">1%</p>
</td>
</tr>
<tr>
<td colspan="2"><strong>Organic</strong></td>
</tr>
<tr>
<td>
<p class="para">Protein</p>
</td>
<td>
<p class="para">18%</p>
</td>
</tr>
<tr>
<td>
<p class="para">Carbohydrate</p>
</td>
<td>
<p class="para">5%</p>
</td>
</tr>
<tr>
<td>
<p class="para">Other organic macromolecules</p>
</td>
<td>
<p class="para">1%</p>
</td>
</tr>
</tbody>
</table>

Biology studies life and living organisms. Biology can be divided into different sections that cover the morphology, physiology, anatomy, behavior, and so on of living organisms.

Biology

Molecules for Life

Discover the fundamental role of chemistry in life, explore the importance of molecules such as water, minerals, and nutrients for plant growth, and learn about the essential organic compounds, such as carbohydrates, lipids, and proteins, as well as enzymes, nucleic acids, and vitamins, and the recommended dietary allowance.


Molecules for Life

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