Chapter 5 – The Structure and Function of Large Biological Molecules

Vocabulary flashcards summarizing essential terms and definitions from the Chapter 5 lecture on large biological molecules.

Macromolecule

A large molecule (carbohydrate, lipid, protein, or nucleic acid) composed of thousands of covalently connected atoms.

Polymer

Long molecule made of many similar or identical building blocks (monomers) linked by covalent bonds.

Monomer

Small building-block molecule that joins with others to form a polymer.

Dehydration (Condensation) Synthesis

Reaction that covalently bonds two monomers by removing a molecule of water; catalyzed by enzymes.

Hydrolysis

Reaction that breaks a polymer into monomers by adding water; reverse of dehydration synthesis.

Carbohydrate

Sugar or sugar polymer serving as fuel or structural material; general formula (CH₂O)n.

Monosaccharide

Simple sugar (e.g., glucose, fructose) that cannot be hydrolyzed to smaller carbohydrates.

Disaccharide

Two monosaccharides joined by a glycosidic linkage (e.g., sucrose, lactose, maltose).

Polysaccharide

Polymer of many monosaccharides linked by glycosidic bonds; used for storage or structure.

Glycosidic Linkage

Covalent bond joining two monosaccharides in a disaccharide or polysaccharide via dehydration.

Starch

Storage polysaccharide in plants made of largely unbranched α-glucose chains stored in plastids.

Glycogen

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

Cellulose

Structural β-glucose polysaccharide forming plant cell walls; molecules aggregate into microfibrils.

Chitin

Nitrogen-containing structural polysaccharide in arthropod exoskeletons and fungal cell walls.

α-Glucose

Ring form of glucose with hydroxyl on C-1 below the plane; monomer of starch and glycogen.

β-Glucose

Ring form of glucose with hydroxyl on C-1 above the plane; monomer of cellulose.

Lipid

Hydrophobic biological molecule (fats, phospholipids, steroids) that does not form polymers.

Fat (Triacylglycerol)

Lipid formed from glycerol and three fatty acids joined by ester linkages; major energy store.

Glycerol

Three-carbon alcohol with three hydroxyl groups; 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 with no C=C double bonds; has maximum H atoms; solid at room temperature.

Unsaturated Fatty Acid

Fatty acid with one or more C=C double bonds; causes kinks; liquid (oil) at room temperature.

Cis Fat

Unsaturated fat whose double bond causes a bend, preventing tight packing of molecules.

Trans Fat

Unsaturated fat with trans double bond; straighter chains that pack tightly and promote plaque.

Hydrogenation

Process of adding hydrogen to unsaturated fats to create saturated (often trans) fats.

Phospholipid

Lipid containing glycerol, two fatty acids, and a phosphate group; amphipathic; forms bilayers.

Amphipathic

Having both hydrophobic and hydrophilic regions (e.g., phospholipids).

Steroid

Lipid with carbon skeleton of four fused rings; includes cholesterol and many hormones.

Cholesterol

Steroid that stabilizes animal cell membranes and is precursor for steroid hormones.

Protein

Biopolymer of amino acids that performs structural, catalytic, transport, signaling, and defensive roles.

Amino Acid

Organic monomer with amino and carboxyl groups plus variable R group; 20 standard types.

Peptide Bond

Covalent bond between carboxyl of one amino acid and amino of another; forms polypeptides.

Polypeptide

Polymer of amino acids linked by peptide bonds; one or more make a protein.

Primary Protein Structure

Linear sequence of amino acids in a polypeptide.

Secondary Protein Structure

Coils (α-helix) or folds (β-pleated sheet) stabilized by hydrogen bonds in backbone.

Tertiary Protein Structure

Three-dimensional shape formed by interactions among R groups, including disulfide bridges.

Quaternary Protein Structure

Association of two or more polypeptide subunits into a functional protein (e.g., hemoglobin).

Disulfide Bridge

Strong covalent bond between two cysteine residues that stabilizes protein tertiary structure.

Denaturation

Loss of a protein’s native shape (and function) due to changes in pH, salt, temperature, etc.

Chaperonin

Protein complex that aids in the correct folding of other proteins within the cell.

Nucleic Acid

Polymer of nucleotides that stores and transmits hereditary information (DNA or RNA).

Nucleotide

Monomer consisting of a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Nucleoside

Nitrogenous base plus pentose sugar, lacking the phosphate group.

Pyrimidine

Single-ring nitrogenous base (cytosine, thymine, uracil).

Purine

Double-ring nitrogenous base (adenine, guanine).

Ribose

Pentose sugar in RNA with hydroxyl group on 2′ carbon.

Deoxyribose

Pentose sugar in DNA lacking the 2′ hydroxyl group.

DNA (Deoxyribonucleic Acid)

Double-stranded, antiparallel nucleic acid storing genetic information; bases A, T, C, G.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid that helps execute genetic instructions; bases A, U, C, G.

Antiparallel

Opposite 5′→3′ orientations of the two strands in a DNA double helix.

Complementary Base Pairing

Specific hydrogen bonding of A with T (or U) and G with C in nucleic acids.

Phosphodiester Bond

Covalent linkage between 3′-OH of one nucleotide and 5′ phosphate of the next; forms nucleic acid backbone.

ATP (Adenosine Triphosphate)

High-energy nucleoside triphosphate that powers cellular work; hydrolyzes to ADP + Pi releasing energy.