BIO 100 - Topic 4: Biological Macromolecules

Organic Molecule

Molecule primarily made of carbon atoms; found in and produced by living organisms

Carbon Versatility

Carbon can form four covalent bonds, allowing for large, complex, and diverse molecules including chains, rings, and branches

Tetravalence of Carbon

Carbon has four valence electrons and can bond with up to four other atoms, creating a tetrahedral geometry

Carbon Skeleton Variations

Can vary in length, branching, double bond position, and ring structures; foundational to organic diversity

Isomer

Compounds with the same molecular formula but different structures and properties

Structural Isomer

Differ in the covalent arrangement of atoms (e.g., straight chain vs branched)

Cis-Trans (Geometric) Isomers

Differ in spatial arrangement around a double bond; cis = same side, trans = opposite sides

Enantiomer

Mirror-image isomers due to an asymmetric (chiral) carbon; differ in biological activity

Chiral Carbon

A carbon bonded to four different atoms or groups; gives rise to enantiomers with different properties

Functional Group

Group of atoms attached to carbon skeletons that affect molecular function and chemical reactivity

Hydroxyl Group (-OH)

Polar functional group; found in alcohols; increases solubility in water

Carbonyl Group (C=O)

Found in aldehydes (end of chain) and ketones (within chain); involved in reactivity

Carboxyl Group (-COOH)

Acts as an acid; found in amino acids and fatty acids; can donate H⁺

Amino Group (-NH2)

Acts as a base; found in amino acids; can pick up H⁺

Sulfhydryl Group (-SH)

Forms disulfide bonds in proteins; stabilizes protein structure

Phosphate Group (-PO4)

Negatively charged; involved in energy transfer (e.g., ATP); contributes to nucleic acid structure

Methyl Group (-CH3)

Nonpolar; affects gene expression when added to DNA (epigenetic regulation)

Macromolecule

Large biological molecule formed by joining smaller organic molecules (monomers) through polymerization

Polymer

Long molecule consisting of many monomers linked by covalent bonds

Monomer

Small, repeating unit that serves as the building block of a polymer

Dehydration Reaction

Chemical reaction that joins monomers by removing a water molecule; builds polymers

Hydrolysis

Chemical reaction that breaks polymers by adding water; used in digestion and decomposition

Carbohydrate

Macromolecule made of carbon, hydrogen, and oxygen; primary source of energy for organisms

Monosaccharide

Simple sugar (e.g., glucose, fructose); monomer of carbohydrates

Glucose

A 6-carbon sugar that is the main source of energy for cells; C6H12O6

Disaccharide

Two monosaccharides joined by a glycosidic linkage (e.g., sucrose = glucose + fructose)

Polysaccharide

Long carbohydrate molecule made of many monosaccharides; used for energy storage or structure

Starch

Storage polysaccharide in plants; composed of alpha-glucose; helical structure

Glycogen

Storage polysaccharide in animals; found in liver and muscle; highly branched structure

Cellulose

Structural polysaccharide in plant cell walls; composed of beta-glucose; straight and rigid

Difference Between Starch and Cellulose

Starch has alpha-1,4 linkages; cellulose has beta-1,4 linkages, making cellulose indigestible to most animals

Lipids

Hydrophobic macromolecules including fats, phospholipids, and steroids; used for energy storage and membrane structure

Fat (Triglyceride)

Consists of glycerol and three fatty acids; formed via dehydration reaction

Saturated Fat

Has no double bonds between carbon atoms in fatty acid chains; solid at room temperature (e.g., butter)

Unsaturated Fat

Has one or more double bonds; causes kinks in fatty acid chains; liquid at room temperature (e.g., olive oil)

Trans Fat

Artificially hydrogenated fat with trans double bonds; raises LDL (bad cholesterol)

Phospholipid

Molecule with a hydrophilic (polar) phosphate head and two hydrophobic fatty acid tails; forms cell membranes

Phospholipid Bilayer

Double layer of phospholipids with heads facing outward and tails inward; forms the structure of cell membranes

Steroid

Lipid with four fused carbon rings; includes cholesterol and hormones like testosterone and estrogen

Cholesterol

Type of steroid in animal cell membranes; maintains fluidity and stability

Proteins

Polymers of amino acids with diverse functions including enzymes, transport, defense, signaling, and structure

Amino Acid

Monomer of proteins; composed of a central carbon, hydrogen, amino group, carboxyl group, and R group

Peptide Bond

Covalent bond formed between amino acids during protein synthesis via dehydration reaction

Polypeptide

Chain of amino acids linked by peptide bonds; folds to form functional protein

Levels of Protein Structure

Primary (sequence), secondary (alpha helix/beta sheet), tertiary (3D folding), quaternary (multiple polypeptides)

Denaturation

Process in which a protein loses its shape and function due to heat, pH, or chemicals disrupting its structure

Chaperonins

Proteins that assist the proper folding of other proteins inside cells

Nucleic Acids

Macromolecules that store genetic information; DNA and RNA

DNA

Deoxyribonucleic acid; double-stranded; stores hereditary information; bases A, T, C, G

RNA

Ribonucleic acid; single-stranded; involved in protein synthesis; bases A, U, C, G

Nucleotide

Monomer of nucleic acids; made of a nitrogenous base, sugar (ribose or deoxyribose), and phosphate group

Phosphodiester Bond

Covalent bond that links nucleotides in nucleic acids between phosphate and sugar groups

Base Pairing in DNA

Adenine pairs with thymine (A-T), cytosine pairs with guanine (C-G)

Gene Expression

The process of converting DNA instructions into functional proteins or RNA