Chapter 5 – The Structure and Function of Macromolecules

Vocabulary flashcards covering key terms from the lecture on carbohydrates, lipids, proteins, and nucleic acids, their structures, functions, and related biochemical concepts.

Macromolecule

A very large molecule (often >100,000 Da) belonging to one of four major classes: carbohydrates, lipids, proteins, or nucleic acids.

Polymer

A long molecule composed of many similar or identical monomers linked by covalent bonds.

Monomer

A small molecule that serves as a building block of a polymer.

Dehydration (Condensation) Reaction

Chemical process that joins two monomers by removing a water molecule; requires enzymes and energy.

Hydrolysis

Reaction that breaks covalent bonds in polymers by the addition of water; reverse of dehydration.

Carbohydrate

A sugar or sugar polymer that serves as fuel or building material; includes monosaccharides, disaccharides, and polysaccharides.

Monosaccharide

Simple sugar with molecular formula multiples of CH₂O; e.g., glucose (C₆H₁₂O₆).

Disaccharide

Sugar formed by two monosaccharides joined via a glycosidic linkage; e.g., maltose, sucrose, lactose.

Polysaccharide

Polymer of many monosaccharides linked by glycosidic bonds; functions in storage or structural support.

Glycosidic Linkage

A covalent bond joining two monosaccharides after dehydration.

Starch

Storage polysaccharide of plants composed of α-glucose; includes amylose and amylopectin.

Glycogen

Highly branched storage polysaccharide of animals, stored mainly in liver and muscle.

Cellulose

Structural polysaccharide of β-glucose in plant cell walls; forms microfibrils and is indigestible to most animals.

Chitin

Structural polysaccharide with nitrogen appendages; forms arthropod exoskeletons and fungal cell walls.

Lipid

Hydrophobic biological molecule, including fats, phospholipids, and steroids; not true polymers.

Fat (Triacylglycerol)

Lipid consisting of three fatty acids ester-linked to glycerol; energy storage, insulation, cushioning.

Glycerol

Three-carbon alcohol with a hydroxyl group on each carbon; backbone of fats and phospholipids.

Fatty Acid

Long hydrocarbon chain with a terminal carboxyl group; can be saturated or unsaturated.

Saturated Fatty Acid

Fatty acid lacking C=C double bonds; straight chain; produces solid fats at room temperature.

Unsaturated Fatty Acid

Fatty acid with one or more C=C double bonds; kinks prevent tight packing; liquid oils.

Trans Fat

Unsaturated fat with trans double bonds created during hydrogenation; increases atherosclerosis risk.

Hydrogenation

Industrial addition of hydrogen to unsaturated fats, converting them to saturated and trans fats.

Atherosclerosis

Cardiovascular disease characterized by plaque buildup in arteries, promoted by saturated and trans fats.

Phospholipid

Lipid with two fatty acids and a phosphate-containing head; major component of cell membranes.

Micelle

Spherical phospholipid aggregate formed in water with hydrophobic tails inward and hydrophilic heads outward.

Phospholipid Bilayer

Double-layered arrangement of phospholipids with hydrophobic tails inside and hydrophilic heads outside; foundation of membranes.

Steroid

Lipid with four fused carbon rings; functional groups create different steroids.

Cholesterol

Key steroid in animal membranes and precursor of other steroids; excess elevates cardiovascular risk.

Protein

Functional biological molecule made of one or more polypeptides folded into specific conformations.

Amino Acid

Monomer of proteins; contains amino group, carboxyl group, hydrogen, and variable R group around an α-carbon.

Peptide Bond

Covalent bond formed by dehydration between carboxyl of one amino acid and amino of another.

Polypeptide

Polymer of amino acids linked by peptide bonds; folds to form a protein.

Primary Structure

Linear sequence of amino acids in a polypeptide.

Secondary Structure

Regular coils or folds (α-helix, β-pleated sheet) stabilized by hydrogen bonds in the backbone.

Alpha Helix

Right-handed coil secondary structure held by backbone hydrogen bonds.

Beta Pleated Sheet

Sheetlike secondary structure formed by hydrogen-bonded strands; gives silk its strength.

Tertiary Structure

Overall 3-D shape of a polypeptide formed by interactions among R groups (hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals).

Disulfide Bridge

Strong covalent bond between sulfhydryl groups of two cysteines stabilizing tertiary structure.

Quaternary Structure

Protein structure arising when two or more polypeptide subunits assemble; e.g., collagen, hemoglobin.

Denaturation

Loss of protein conformation and function due to pH, salt, temperature, or solvent changes.

Chaperonin (Chaperone Protein)

Protein complex that shelters polypeptides to ensure proper folding without specifying final structure.

Nucleic Acid

Polymer of nucleotides that stores or transmits hereditary information; DNA or RNA.

Nucleotide

Monomer of nucleic acids; composed of a nitrogenous base, pentose sugar, and phosphate group.

Nucleoside

Nitrogenous base plus pentose sugar without phosphate.

Purine

Nitrogenous base with two fused rings; adenine (A) or guanine (G).

Pyrimidine

Single-ring nitrogenous base; cytosine (C), thymine (T), or uracil (U).

Phosphodiester Linkage

Covalent bond joining nucleotides between 3′ OH of one sugar and 5′ phosphate of the next.

DNA (Deoxyribonucleic Acid)

Double-stranded nucleic acid with deoxyribose sugar; stores genetic information and can replicate itself.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid with ribose sugar; functions in gene expression (e.g., mRNA, tRNA, rRNA).

Double Helix

Two antiparallel DNA strands wound around an axis and held by complementary base pairing.

Antiparallel

Orientation of DNA strands running in opposite 5′→3′ directions.

Complementary Base Pairing

Specific hydrogen bonding: A with T (or U in RNA) and G with C.

Gene

DNA segment that codes for a functional product (usually a polypeptide or RNA molecule).

Messenger RNA (mRNA)

RNA that carries genetic information from DNA to ribosomes for protein synthesis.

Ribosome

Cellular structure where mRNA-directed protein synthesis (translation) occurs.

Flow of Genetic Information

DNA → RNA → Protein; central dogma of molecular biology.

Molecular Genealogy

Use of DNA/protein sequence comparisons to infer evolutionary relationships among species.