Rucete ✏ Campbell Biology In a Nutshell
At its core, everything in the universe—living or non-living—is made of matter. Whether it’s a towering redwood tree, a drop of water, or the air we breathe, it all boils down to chemical elements and compounds. Understanding these fundamental substances helps us grasp how life functions at a molecular level.
Unit 1 THE CHEMISTRY OF LIFE
Concept 2.1 Matter consists of chemical elements in pure form and in combinations called compounds
What is Matter?
Matter is anything that takes up space and has mass. It exists in many forms—solids, liquids, gases—and makes up everything around us, including our own bodies.
But what’s matter made of? Elements.
Elements: The Purest Forms of Matter
An element is a pure substance that cannot be broken down into simpler substances by chemical reactions. Each element is made up of one type of atom, and there are 92 naturally occurring elements on Earth.
Some common examples include:
- Oxygen (O) – Found in the air and vital for respiration
- Carbon (C) – The backbone of all life
- Hydrogen (H) – Found in water and organic molecules
- Nitrogen (N) – Essential for DNA and proteins
Together, these four elements—oxygen, carbon, hydrogen, and nitrogen—make up about 96% of all living matter. The remaining 4% consists of elements like calcium (Ca), phosphorus (P), potassium (K), and sulfur (S), which are also crucial for life.
Compounds: When Elements Team Up
A compound is a substance formed when two or more elements combine in a fixed ratio. The properties of a compound are often very different from the properties of the elements that make it up.
Take table salt (NaCl) as an example:
- Sodium (Na) is a highly reactive metal.
- Chlorine (Cl) is a toxic gas.
- But together, they form sodium chloride, a safe and essential compound for life.
Another key example is water (H₂O):
- Hydrogen is a flammable gas.
- Oxygen is needed for combustion.
- Combined, they form water, which is vital for life.
This concept is known as emergent properties—when substances form compounds, they can have characteristics that neither of the individual elements had before.
Essential and Trace Elements: What Life Needs
Of the 92 natural elements, only about 20-25% are essential for life. These are called essential elements, meaning that organisms cannot survive without them.
In addition to major elements, some elements are only needed in tiny amounts but are still crucial for survival. These are known as trace elements.
For example:
- Iron (Fe) – Required for oxygen transport in red blood cells.
- Iodine (I) – Essential for thyroid function. Without enough iodine, a person can develop goiter, a condition where the thyroid gland swells.
- Zinc (Zn) – Important for immune function and enzyme activity.
Even though trace elements make up less than 0.01% of body mass, they can have major effects on health and biological function.
When Elements Become Toxic
While some elements are necessary for life, others can be toxic in high amounts. For example:
- Arsenic (As) – Found naturally in some groundwater, it has been linked to severe health issues in humans.
- Lead (Pb) – Can cause neurological damage, especially in children.
- Mercury (Hg) – Can accumulate in fish and harm the nervous system when consumed in high amounts.
Some plants and bacteria have evolved to tolerate or even thrive in environments with high levels of toxic elements, showing how life can adapt over time.
Case Study: Evolution of Tolerance to Toxic Elements
Certain plant species have adapted to grow in serpentine soils, which contain toxic levels of chromium, nickel, and cobalt. Most plants cannot survive in these conditions, but a few have evolved mechanisms to detoxify or store these elements safely.
Scientists believe that natural selection favored random mutations that allowed some plants to survive in these extreme environments. Over time, these plants thrived while others perished, leading to new plant species that are uniquely adapted to these toxic soils.
This is a great example of how evolution shapes life in response to environmental challenges.
In a nutshell - Why This Matters
Understanding elements and compounds is fundamental to biology, chemistry, and life itself. From the air we breathe to the food we eat, everything is made up of combinations of elements that interact in unique ways.
Key takeaways:
✔ Matter is made of elements, which cannot be broken down further.
✔ Compounds form when elements combine, creating substances with new properties.
✔ Essential elements are needed for life, while trace elements are required in small amounts but remain crucial.
✔ Some elements are toxic, but certain organisms have adapted to tolerate them.
In the end, life is just a beautifully complex arrangement of atoms and molecules—and understanding them helps us unlock the mysteries of biology.