Biochemistry Basics for Microbiology

Biochemistry Basics

Atoms and Elements

Atoms are the fundamental units of matter, forming the basis of all chemical substances. Understanding their structure and properties is essential for studying biological molecules and processes.

• Atom: The smallest unit of an element, composed of protons (positively charged), neutrons (neutral), and electrons (negatively charged).

• Atomic Number: The number of protons in an atom; determines the element's identity.

• Atomic Mass: The sum of protons and neutrons in an atom's nucleus.

• Chemical Symbol: The one- or two-letter abbreviation for an element (e.g., Co for cobalt).

Example: Cobalt (Co) has an atomic number of 27 and an atomic mass of 58.933.

Ions and Isotopes

Ions and isotopes are variations of atoms that play important roles in biological and medical contexts.

• Anion: A negatively charged ion formed by gaining electrons.

• Cation: A positively charged ion formed by losing electrons.

• Isotope: Atoms of the same element with different numbers of neutrons. Some isotopes are radioactive and are used in medical diagnostics and treatments.

Example: Radioactive isotopes are used in imaging and cancer therapy.

Molecules, Compounds, and Isomers

Chemical substances can be classified based on their composition and structure.

• Molecule: Two or more atoms bonded together.

• Compound: Molecules composed of more than one type of element.

• Isomer: Molecules with the same molecular formula but different structural arrangements.

Organic vs. Inorganic Compounds

Compounds are categorized based on the presence of carbon and hydrogen.

• Organic Compounds: Contain both carbon and hydrogen (e.g., glucose).

• Inorganic Compounds: May contain carbon or hydrogen, but not both together (e.g., CO2).

Acids, Bases, and pH

Acids and bases influence the pH of solutions, which is critical for biological systems.

• Acid: Releases hydrogen ions (H+) in solution, lowering pH.

• Base: Accepts hydrogen ions or releases hydroxide ions (OH-), raising pH.

pH Scale: Measures the acidity or alkalinity of a solution (0 = most acidic, 14 = most basic).

Chemical Bonds

Ionic and Covalent Bonds

Chemical bonds hold atoms together in molecules and compounds.

• Ionic Bonds: Formed by the transfer of electrons from one atom to another, resulting in attraction between oppositely charged ions. Typically occur between metals and nonmetals.

• Covalent Bonds: Formed when atoms share electrons. Usually occur between nonmetals.

Polar Covalent Bonds and Hydrogen Bonds

Polarity and hydrogen bonding are crucial for the structure and function of biological molecules.

• Polar Covalent Bond: Unequal sharing of electrons creates partial charges within a molecule, leading to polarity.

• Hydrogen Bond: A noncovalent electrostatic attraction between a hydrogen atom (with a partial positive charge) and an electronegative atom (like oxygen or nitrogen) in another molecule or region.

Example: Hydrogen bonds stabilize the structure of DNA and proteins.

Hydrophobic, Hydrophilic, and Amphipathic Substances

• Hydrophobic: Substances that do not readily form hydrogen bonds with water ("water-fearing").

• Hydrophilic: Substances that readily form hydrogen bonds with water ("water-loving").

• Amphipathic: Molecules with both hydrophilic and hydrophobic regions (e.g., phospholipids).

Chemical Reactions

Reactants, Products, and Catalysts

Chemical reactions involve the transformation of reactants into products, often facilitated by catalysts.

• Reactants: The starting substances in a chemical reaction.

• Products: The substances formed as a result of the reaction.

• Catalyst: A substance that increases the rate of a reaction without being consumed.

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis: A reaction that builds complex molecules by joining smaller units and releasing water.

• Hydrolysis: A reaction that breaks down complex molecules by adding water to split covalent bonds.

Activation Energy and Enzymes

• Activation Energy: The minimum energy required to initiate a chemical reaction.

• Enzymes: Biological catalysts that lower activation energy, speeding up biochemical reactions.

Equation:

$\Delta G = G_{products} - G_{reactants}$

(Where $\Delta G$ is the change in free energy.)

Endergonic vs. Exergonic Reactions

• Endergonic Reactions: Require energy input; products have higher energy than reactants.

• Exergonic Reactions: Release energy; products have lower energy than reactants.

Biologically Important Macromolecules

Major Classes and Their Building Blocks

Biological macromolecules are essential for life and are built from smaller subunits.

Macromolecule	Building Block
Carbohydrates	Monosaccharides (simple sugars)
Lipids	Glycerol and up to 3 fatty acids
Nucleic Acids	Nucleotides
Proteins	Amino acids

Types of Bonds in Macromolecules

• Glycosidic Bond: Covalent bond linking monosaccharides in carbohydrates; formed by dehydration synthesis, broken by hydrolysis.

• Peptide Bond: Covalent bond linking amino acids in proteins; formed by dehydration synthesis between amino and carboxyl groups.

• Phosphodiester Bond: Covalent bond linking nucleotides in nucleic acids; forms the sugar-phosphate backbone of DNA and RNA.

Structural and Functional Characteristics

• Carbohydrates: Composed of carbon, hydrogen, and oxygen. Functions include energy storage, structural support, and cell recognition.

• Lipids: Mostly carbon and hydrogen; include fats, oils, and phospholipids. Functions include long-term energy storage, insulation, membrane structure, and signaling.

• Nucleic Acids: Made of nucleotide subunits. DNA and RNA store and transmit genetic information and direct protein synthesis.

• Proteins: Made of amino acids. Functions include catalysis (enzymes), structure, transport, signaling, movement, and immune defense.

Deoxyribonucleotides vs. Ribonucleotides

Feature	Deoxyribonucleotide (DNA)	Ribonucleotide (RNA)
Sugar	Deoxyribose	Ribose
Location	DNA	RNA
Function	Genetic information storage	Genetic information transfer and protein synthesis

Lipid Saturation

• Saturated Lipids: No double bonds; straight chains; solid at room temperature.

• Unsaturated Lipids: One or more double bonds; bent chains; liquid at room temperature.

Levels of Protein Structure

• Primary Structure: Sequence of amino acids in a polypeptide chain.

• Secondary Structure: Local folding into alpha helices and beta sheets via hydrogen bonds.

• Tertiary Structure: Overall 3D shape of a single polypeptide chain.

• Quaternary Structure: Association of multiple polypeptide chains into a functional protein.

Example: Hemoglobin has quaternary structure, consisting of four polypeptide subunits.