Chemistry of Microbiology Chapter 2

Chapter 2: Chemistry of Microbiology

• Atoms are the fundamental units of matter
• Matter is anything that occupies space and has mass
• Atomic structure includes the nucleus (containing protons and neutrons), and electrons orbiting the nucleus in electron shells
• Electrons determine an atom's chemical behavior
• Electrons occupy electron shells
• Valence electrons interact with other atoms
• The atomic number equals the number of protons in the nucleus
• The atomic mass (atomic weight) is the sum of the masses of protons, neutrons, and electrons
• Isotopes are atoms of the same element that differ in the number of neutrons
• Chemical bonds form when atoms share or transfer valence electrons
• Molecules are formed from two or more atoms held together
• Compounds are molecules consisting of more than one element

Chemical Bonds

• Covalent bonds involve the sharing of electron pairs between atoms.
• Nonpolar covalent bonds involve equal sharing of electrons resulting in no poles
• Polar covalent bonds involve unequal sharing of electrons resulting in partial charges
• Electronegativity is the attraction of an atom for electrons
• The more electronegative an atom, the greater the pull exerted on electrons
• Ionic bonds form when electrons are transferred from one atom to another, creating ions that attract each other
• Cations are positively charged ions, anions are negatively charged ions
• Ionic compounds typically form crystalline structures called salts
• Hydrogen bonds are weak attractions between a hydrogen atom carrying a partial positive charge and an atom with a partial negative charge

Chemical Reactions

• Chemical reactions involve the making or breaking of chemical bonds between molecules
• Reactants are substances that enter into a chemical reaction
• Products are substances that are formed by the reaction
• Synthesis reactions form larger molecules from smaller ones
• Common type is dehydration synthesis
• Decomposition reactions break down larger molecules into smaller ones
• Common type is hydrolysis

Water, Acids, Bases, and Salts

• Water is the most abundant substance in organisms
• Water's special properties arise from its polar covalent bonds
• Water's cohesiveness leads to surface tension
• Water is an excellent solvent
• Water remains liquid across a wide temperature range
• Water can absorb significant heat energy without changing temperature
• Water participates in many chemical reactions
• Salts are compounds that dissociate in water into cations and anions other than H+ and OH-
• Salt cations and anions are electrolytes, creating electrical differences in the cell
• Electrolytes transfer electrons and form components of many enzymes

Organic Macromolecules

• Lipids are hydrophobic and include fats, terpenes, phospholipids, and waxes

• Fats (triglycerides) consist of glycerol and fatty acids

• Phospholipids have a hydrophilic head and hydrophobic tails, forming bilayers in cell membranes

• Waxes contain long-chain fatty acids covalently linked to long-chain alcohols; they are hydrophobic and insoluble in water

• Carbohydrates serve as energy sources and structural components, including monosaccharides, disaccharides, and polysaccharides

• Monosaccharides are simple sugars such as glucose

• Disaccharides are formed from two monosaccharides linked together via dehydration synthesis (e.g., sucrose)

• Polysaccharides are long chains of monosaccharides (e.g., cellulose, starch, glycogen)

• Proteins are composed mostly of carbon, hydrogen, oxygen, nitrogen, and sulfur

• Proteins play various roles like structure, catalysis, regulation, transport, and defense

• Amino acids are the building blocks of proteins

• Side groups of amino acids affect protein interactions

• Covalent peptide bonds link amino acids

• Protein structure has four levels: primary (amino acid sequence), secondary (alpha helix and beta sheets), tertiary (3D shape), and quaternary (multiple polypeptide chains)

• Nucleic acids store and transmit genetic information, including DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

• DNA is a double helix, while RNA typically is single-stranded

• Nucleotides are the building blocks of nucleic acids consisting of a phosphate group, a pentose sugar, and a nitrogenous base

• ATP (adenosine triphosphate) is a nucleotide that stores and releases energy in cells