4 min read•june 18, 2024
Danna Esther Gelfand
Jillian Holbrook
Danna Esther Gelfand
Jillian Holbrook
Organisms, such as ourselves, are made up of , which takes up space and has mass. Matter is made up of tiny particles called , which are made up of even smaller particles called , , and . Atoms can be combined in various ways to form different types of matter, such as solids, liquids, and gases, and to make up different elements, which are substances that cannot be broken down further by chemical reactions. Although there is an entire Periodic Table of Elements, for AP Biology, the essential elements to know are , , , , , , , , , , and .
are substances that can be broken down further by chemical reactions because they are made of two or more elements that are in a fixed ratio to each other. For example, we learned previously that water, H2O, is made of two hydrogens and one oxygen. Because there is a fixed ratio of hydrogens and oxygen, water is a compound.
Living systems and the organisms in them require constant exchanges of energy and . Exchanging matter is what allows an organism to grow and reproduce. By understanding atoms and molecules, we can understand the basis of the elements of life!
An element's properties are retained by the smallest unit of mass, called an atom. The subatomic particles that compose atoms are protons (positive charge), neutrons (neutral/no electrical charge), and electrons (negative charge).
The of an element is determined by the number of protons in the nucleus. In the figure below, the number six is the atomic number of carbon. The is the sum of the protons and neutrons in the nucleus. The atomic mass number from the figure is 12.011.
are two atoms of an element that have a different number of neutrons. are used for processes that include fossil dating and medical imaging. They decay spontaneously and release energy. An example of a radioactive isotope that is used for dating sites, fossils, and artifacts is , or , which has an atomic nucleus containing six protons and eight neutrons.
An electron's potential energy (location/structure) is called an or electron shell. When electrons absorb energy, they move up or jump an energy level farther away from the nucleus. When electrons release energy, they move closer to the nucleus.
Carbon is the building block of the major macromolecules/organic molecules: carbohydrates, lipids, proteins, and . It is a major component of compounds and helps form cells in organisms.
Why is carbon such an important biological element? Carbon has the unique ability to form four covalent bonds, which is known as . The goal for all atoms is to be stable, and carbon is a stable element that readily bonds with a variety of other elements. Carbon must find four more electrons to fill its outer shell, giving a total of eight electrons to satisfy the . The octet rule states that atoms will lose, gain or share electrons to achieve an electron configuration of eight valence electrons. (e.g CH4 methane)
Nitrogen is a building block in proteins, nucleic acids, , and . These molecules play crucial roles in many biological processes, including metabolism, cell division, and DNA replication. Nitrogen is even a component of many hormones, such as and .
In addition to its role in the synthesis of biological molecules, nitrogen is also important in the environment. Nitrogen is a key element in the , which plays a crucial role in the balance of nutrients in ecosystems. While nitrogen is primarily in the atmosphere as a gas, plants and some microorganisms can convert atmospheric nitrogen into a usable form for other organisms through , which is essential for the overall functioning of ecosystems.
is also a useful element in biology because it is a key component of nucleic acids, certain proteins, and lipids. Beyond its role in , which are essential components of the genetic material in all living organisms, phosphorus is also involved in biological processes like energy production. It also plays a crucial role in the balance of nutrients in ecosystems.
are accessory elements that give molecules a different structure, therefore, a different function. They can be classified as hydrophobic or hydrophilic based on their charge and polarity characteristics.
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Check out the AP Bio Unit 1 Replays or watch the 2021 Unit 1 Cram