The Chemistry of Organic Molecules (Chapter 3)

Vocabulary flashcards covering core concepts from the notes on organic molecules, their structures, functions, and essential biochemical processes.

Biomolecules

The four major classes of organic molecules in living organisms: carbohydrates, lipids, proteins, and nucleic acids.

Organic molecule

Molecule that contains carbon and hydrogen atoms; carbon commonly forms up to four covalent bonds.

Carbon’s bonding versatility

Can form single, double, or triple bonds; can create long chains, rings, and diverse structures; bonds can be polar or nonpolar.

Line-angle formula

A schematic where line endpoints imply carbons; hydrogen attached to carbons is usually omitted.

Functional group

Atoms or groups with characteristic chemical behavior that determine reactivity and polarity of organic molecules.

Hydroxyl group

R–OH; polar; forms hydrogen bonds; common in sugars and some amino acids.

Carbonyl group

C=O; includes aldehydes (R–CHO) and ketones (R–CO–R); polar; present in sugars.

Carboxyl group

–COOH; acidic; polar; found in fatty acids and amino acids.

Amino group

–NH2; polar; basic; present in amino acids.

Sulfhydryl group

–SH; thiol; forms disulfide bonds; present in some amino acids.

Phosphate group

–O–P(=O)(–OH)–; polar; acidic; found in nucleotides and phospholipids.

Isomer

Molecules with identical formulas but different arrangements of atoms.

Monomer

A single subunit that can join with others to form polymers (e.g., amino acids, monosaccharides, nucleotides).

Polymer

A large molecule made of repeating monomers; lipids are not true polymers.

Dehydration synthesis

Joining monomers with removal of water to form covalent bonds.

Hydrolysis

Breaking covalent bonds by adding water to polymers.

Enzyme

Biological catalyst; speeds up reactions without being consumed or permanently altered.

Lactose intolerance

Inability to digest lactose due to insufficient lactase enzyme.

Carbohydrate functions

Energy source and building material; general formula Cn(H2O)n; 1:2:1 ratio.

Monosaccharide

Single sugar; 3–7 carbon atoms; e.g., glucose, fructose, galactose; hexoses and pentoses.

Disaccharide

Two monosaccharides joined by dehydration; e.g., lactose, sucrose, maltose.

Polysaccharide

Polymers of monosaccharides; includes starch, glycogen, cellulose, chitin, peptidoglycan.

Starch

Plant polysaccharide for energy storage (amylose and amylopectin).

Glycogen

Animal storage polysaccharide for energy.

Cellulose

Structural polysaccharide in plant cell walls; indigestible by most animals.

Chitin

Structural polysaccharide in fungal cell walls and some animal exoskeletons.

Peptidoglycan

Structural polysaccharide in bacterial cell walls.

Lipids

Large, nonpolar molecules insoluble in water; include fats, oils, phospholipids, steroids, waxes; diverse functions.

Triglyceride

Glycerol linked to three fatty acids via dehydration synthesis; main long-term energy storage form.

Fatty acid saturation

Saturated: no double bonds, usually solid; Unsaturated: one or more double bonds, usually liquid; cis/trans configurations affect properties.

Phospholipid

Glycerol + two fatty acids + a phosphate-containing head; hydrophobic tails and hydrophilic head; form phospholipid bilayers.

Steroid

Four fused carbon rings; cholesterol as membrane component; precursors to hormones like testosterone and estrogen.

Waxes

Long-chain fatty acids linked to alcohols; waterproof, protective molecules.

Proteins

Polymers of amino acids joined by peptide bonds; polypeptides fold into functional proteins.

Amino acid

Amino group + carboxyl group + unique R group; 20 standard amino acids with varying properties.

Peptide bond

Covalent bond linking amino acids via dehydration synthesis.

Primary structure

Linear sequence of amino acids in a polypeptide.

Secondary structure

Alpha helices or beta pleated sheets stabilized by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a protein due to hydrophobic, ionic, hydrogen, and covalent interactions.

Quaternary structure

Two or more polypeptides arranged to form a functional protein.

Chaperone proteins

Molecules that assist protein folding and can help prevent misfolding.

Prions

Misfolded proteins linked to fatal brain diseases (transmissible spongiform encephalopathies).

Nucleic acids

DNA and RNA; polymers of nucleotides; store/express genetic information.

Nucleotide

Phosphate group + pentose sugar + nitrogenous base; building block of nucleic acids.

Purines

Adenine and Guanine; larger, two-ring bases.

Pyrimidines

Cytosine, Thymine (DNA), and Uracil (RNA); single-ring bases.

Complementary base pairing

Adenine pairs with Thymine (DNA) or Uracil (RNA); Guanine pairs with Cytosine; bases pair to form DNA/RNA structure.

DNA structure

Double helix with sugar–phosphate backbone; base pairing A–T and G–C; antiparallel strands.

RNA structure

Single-stranded nucleic acid; sugar is ribose; bases A, G, C, U.

ATP (adenosine triphosphate)

High-energy nucleotide with three phosphate groups; hydrolysis releases energy for cellular work.

ADP

Adenosine diphosphate; product of ATP hydrolysis plus an inorganic phosphate.