Lecture Notes: Molecular Biology - Vocabulary Flashcards

Vocabulary flashcards covering key terms from the lecture notes on organic molecules, biomolecules, and lipids.

Carbon

Element central to organic molecules; tetravalent and forms up to four covalent bonds.

Valence

The number of bonds an element can form; carbon has valence 4.

Lewis dot structure

Diagram showing valence electrons around an atom.

Valence electrons

Electrons in the outermost shell that participate in bonding.

Covalent bond

Bond formed by sharing electrons between atoms.

Methane

CH4; simplest hydrocarbon, illustrating carbon’s tetravalence.

Hydrocarbon

Organic compound composed only of carbon and hydrogen.

Isomer

Compounds with the same molecular formula but different structures.

Unbranched

Linear carbon chain with no side branches.

Branched

Carbon chain with side branches.

Cyclohexane

Cycloalkane with a six-member ring.

Aromatic

Ring structure with delocalized electrons (e.g., benzene).

Functional group

Atom group that imparts characteristic properties and reactivity.

Hydroxyl group

–OH; polar; forms hydrogen bonds; hydrophilic.

Carbonyl group

C=O; polar; present in ketones and aldehydes.

Aldehyde

Carbonyl group at the end of a carbon chain (R-CHO).

Ketone

Carbonyl group within a carbon chain (R-CO-R').

Carboxyl group

–COOH; acidic; ionizes to –COO−; hydrophilic.

Amino group

–NH2; acts as a base; hydrophilic; present in amino acids and proteins.

Amide group

–C(=O)NH–; polar; hydrophilic; found in proteins.

Phosphate group

–OPO3H2; hydrophilic; ionizes; found in phospholipids, nucleic acids, ATP.

Sulfhydryl group

–SH; weakly polar; reactive; forms disulfide bonds in proteins.

Methyl group

–CH3; nonpolar; influences structure and reactivity.

Polar

Molecule with partial charges; interacts with water.

Hydrophilic

Water-loving; polar or charged; dissolves in water.

Hydrophobic

Water-fearing; nonpolar; resists mixing with water.

Steroid

Lipid with four fused carbon rings; signaling molecules (e.g., testosterone, estradiol).

Carbohydrates

Saccharides; polymers; primary energy source and structural components; C:H:O = 1:2:1; CnH2nOn.

Monosaccharide

Single sugar unit; e.g., glucose; simplest carbohydrate.

Disaccharide

Two monosaccharides linked; e.g., maltose, lactose, sucrose.

Polysaccharide

Many sugar units; starch, glycogen, cellulose.

Glycosidic linkage

Bond joining sugar units; examples: 1-4, 1-2 linkages.

Starch

Plant energy storage polysaccharide; consists of amylose (unbranched) and amylopectin (branched).

Amylose

Unbranched component of starch.

Amylopectin

Branched component of starch.

Glycogen

Animal storage polysaccharide; highly branched.

Cellulose

Plant structural polysaccharide; unbranched; forms plant cell walls.

Glucose

C6H12O6; primary energy source; simple sugar.

Proteins

Macromolecules with diverse functions: enzymes, defense, transport, etc.

Amino acid

Monomer of proteins; contains amino group, carboxyl group, and an R group.

R group

Variable side chain; determines properties of amino acids.

Nonpolar (hydrophobic) side chains

Gly, Ala, Val, Leu, Ile, Met, Phe, Trp, Pro; hydrophobic.

Polar (hydrophilic) side chains

Ser, Thr, Cys, Tyr, Asn, Gln; hydrophilic.

Basic (positively charged) side chains

Lys, Arg, His; positively charged at physiological pH.

Acidic (negatively charged) side chains

Asp, Glu; negatively charged at physiological pH.

Peptide bond

Covalent bond linking amino acids via dehydration synthesis.

N-terminus

Free amino end of a polypeptide.

C-terminus

Free carboxyl end of a polypeptide.

Nucleic acids

Informational polymers made of nucleotides.

Nucleotide

Monomer of nucleic acids; sugar + phosphate + nitrogenous base.