BackChemistry of Microbiology: Atomic Structure, Elements, and Chemical Bonds
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Chemistry of Microbiology
Introduction to Matter and Atoms
The study of microbiology requires a foundational understanding of chemistry, as all living organisms are composed of chemical substances. Matter and atoms are the basic building blocks of all substances.
Matter: Anything that takes up space and has mass.
Atoms: The smallest chemical units of matter, consisting of a nucleus (containing protons and neutrons) and electrons that orbit in electron shells.
Proton (p+): Positively charged particle in the nucleus.
Neutron (n0): Neutrally charged particle in the nucleus.
Electron (e-): Negatively charged particle found in electron shells around the nucleus.
Example: The diagram of an atom shows electrons in shells around a nucleus made of protons and neutrons.
Essential Elements of Life
Elements Required for Living Organisms
Only a subset of the elements found on Earth are essential for life. These elements are fundamental to the structure and function of biological molecules.
About 25 out of 92 naturally occurring elements are essential to life.
Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N), Phosphorus (P), and Sulfur (S) make up approximately 99% of the dry weight of living matter.
Other important elements include Calcium (Ca), Potassium (K), Zinc (Zn), Iron (Fe), Sodium (Na).
Example: The periodic table highlights the elements most commonly found in living organisms.
Chemical Bonds
Covalent Bonds
Chemical bonds are the forces that hold atoms together in molecules. Covalent bonds are especially important in biological molecules.
Covalent Bond: The sharing of a pair of electrons by two atoms.
Electronegativity: The attraction of an atom for electrons; the more electronegative an atom, the greater the pull its nucleus exerts on electrons.
Example: Two hydrogen atoms share electrons to form a hydrogen molecule (H2); two oxygen atoms share electrons to form an oxygen molecule (O2).
Preferred Covalent Bonds in Biochemistry
Biological molecules are formed by atoms that have characteristic numbers of covalent bonds.
Atom | # Covalent Bonds |
|---|---|
Sulphur (S) | 2 |
Phosphorus (P) | 5 |
Oxygen (O) | 2 |
Nitrogen (N) | 3 |
Carbon (C) | 4 |
Hydrogen (H) | 1 |
Example: The acronym "SPONCH" helps remember the main atoms in biochemistry and their bonding patterns.
Nonpolar Covalent Bonds
Nonpolar covalent bonds occur when electrons are shared equally between atoms with similar electronegativities. These bonds are important in organic molecules.
Nonpolar Covalent Bond: Shared electrons spend equal amounts of time around each nucleus; no poles exist.
Carbon atoms: Critical to life; form four nonpolar covalent bonds with other atoms.
Organic Compounds: Molecules that contain both carbon and hydrogen atoms.
Example: Hydrogen gas (H2) is formed by two hydrogen atoms sharing electrons equally.
*Additional info: These foundational concepts are essential for understanding the molecular basis of microbial life, including the structure and function of biomolecules such as proteins, nucleic acids, carbohydrates, and lipids.*
