The Structure and Function of Large Biological Molecules

Vocabulary flashcards covering key terms from the lecture notes on macromolecules, their building blocks, structures, and nucleic acids.

Macromolecule

A very large molecule such as a protein, carbohydrate, lipid, or nucleic acid—typically a polymer made of many monomers.

Monomer

A small subunit that can join with others to form a polymer.

Polymer

A large molecule composed of many repeated subunits (monomers) linked by covalent bonds.

Dehydration reaction

A reaction that links monomers by removing a water molecule, forming a covalent bond.

Hydrolysis

A reaction that breaks polymers into monomers by adding a water molecule.

Carbohydrates

Sugars and their polymers; provide energy and structural support; include monosaccharides, disaccharides, and polysaccharides.

Monosaccharide

The simplest carbohydrate; a single sugar molecule (e.g., glucose) with formula typically CH2O.

Glucose

Most common monosaccharide; chemical formula C6H12O6; major cellular fuel.

Glycosidic linkage

Covalent bond joining monosaccharides to form disaccharides and polysaccharides.

Disaccharide

A carbohydrate composed of two monosaccharides (e.g., sucrose).

Polysaccharide

A polymer composed of many sugar monomers joined by glycosidic linkages.

Starch

Plant storage polysaccharide made of glucose; stored in plastids.

Glycogen

Animal storage polysaccharide made of glucose; stored mainly in liver and muscles.

Amylose

Unbranched storage polysaccharide in starch; forms a helix.

Amylopectin

Branched storage polysaccharide in starch.

Cellulose

Structural polysaccharide in plant cell walls; most abundant organic molecule on Earth.

Chitin

Structural polysaccharide in arthropod exoskeletons and fungal cell walls; similar to glucose with an N-containing group.

Lipids

Hydrophobic organic molecules not true polymers; include fats, phospholipids, and steroids.

Fats (triglycerides)

Energy-storing lipids built from glycerol and three fatty acids via ester linkages.

Glycerol

Three-carbon alcohol that bears a hydroxyl group on each carbon.

Fatty acid

Hydrocarbon with a terminal carboxyl group; varies in length and degree of unsaturation.

Saturated fatty acid

Fatty acid with only single bonds; packs tightly; solid at room temperature.

Unsaturated fatty acid

Fatty acid with one or more double bonds; creates kinks and liquids at room temperature.

Ester linkage

Bond linking a glycerol to a fatty acid in fats.

Phospholipids

Major structural component of cell membranes; glycerol with two fatty acids and a phosphate group; hydrophobic tails, hydrophilic heads.

Phospholipid bilayer

Double-layered membrane formed by phospholipids; hydrophobic tails inward, hydrophilic heads outward.

Steroids

Lipids with a four-ring carbon skeleton; include cholesterol and hormones.

Cholesterol

An essential membrane component in animals; precursor to other steroids; can contribute to disease at high levels.

Protein

Macromolecule with diverse functions; enzymes, storage, hormones, transport, defense, structure, and more.

Amino acid

Basic building blocks of proteins; contain amino group, carboxyl group, hydrogen, and a variable R group.

Peptide bond

Covalent bond formed by a dehydration reaction between the carboxyl of one amino acid and the amino group of another.

Polypeptide

A polymer of amino acids linked by peptide bonds; can be 40 to thousands of residues long.

Primary structure

Linear sequence of amino acids in a polypeptide.

Secondary structure

Regular folds along the backbone (alpha helix and beta pleated sheet) formed by hydrogen bonds.

Alpha helix

A right-handed helical secondary structure in proteins.

Beta pleated sheet

A secondary structure with strands connected by hydrogen bonds, forming a sheet.

Tertiary structure

Overall three-dimensional shape of a polypeptide arising from R-group interactions.

Disulfide bridge

Strong covalent bond between sulfhydryl (-SH) groups of cysteine residues, stabilizing structure.

Quaternary structure

Structure formed when two or more polypeptide subunits assemble into a functional protein.

Hemoglobin

Globular protein with four subunits; each has a heme group with iron that binds oxygen.

Collagen

Fibrous protein consisting of three polypeptides; provides connective tissue support.

Sickle-cell disease

Inherited disorder caused by a single amino acid substitution in hemoglobin; deforms red blood cells and impairs oxygen transport.

Denaturation

Unfolding of a protein due to changes in pH, salt, or temperature; loss of function.

DNA

Deoxyribonucleic acid; hereditary material; polymer of nucleotides; stores genetic information.

RNA

Ribonucleic acid; assists in building proteins and regulating gene expression; polymer of nucleotides.

Nucleotide

Monomer of nucleic acids; consists of sugar, nitrogenous base, and phosphate group.

Nucleic acid

Polymers of nucleotides; includes DNA and RNA.

Deoxyribose

Five-carbon sugar in DNA.

Ribose

Five-carbon sugar in RNA.

Complementary base pairing

A pairs with T (or U in RNA) and G pairs with C via hydrogen bonds.