Chapter 2 Notes/Flashcards

Water

A polar solvent that forms hydrogen bonds; each water molecule can form up to four H‑bonds, giving water its unique properties (high surface tension, high boiling point, high specific heat, high heat of vaporization).

Macromolecule

A large biomolecule that is a polymer formed from monomers (e.g., carbohydrates, proteins, nucleic acids, lipids as fatty-acid–based units).

Monomer

A small unit that can join with others to form a polymer (e.g., monosaccharide, amino acid, nucleotide).

Polymer

A large molecule composed of repeating monomer units connected by covalent bonds (e.g., polysaccharides, proteins, nucleic acids).

Monosaccharide

A simple sugar; the building block of carbohydrates (formula often (CH2O)n, n=3–6).

Polysaccharide

A polymer of monosaccharides; used for energy storage (glycogen, starch) or structure (cellulose).

Glycogen

A branched polymer of glucose used for energy storage in animals.

Starch

A glucose polysaccharide used for energy storage in plants.

Cellulose

A structural carbohydrate in plant cell walls with beta-1,4 linkages; indigestible by humans but digestible by some ruminants with cellulase enzymes.

Beta-1,4 linkage

A type of glycosidic bond between glucose units in cellulose, formed by cellulose synthase.

Lipids

A diverse class of hydrophobic or amphipathic molecules important for energy storage, membranes, and signaling; not true polymers like carbohydrates or proteins.

Fatty Acid

A long hydrocarbon chain with a terminal carboxyl group; hydrophobic chain with hydrophilic carboxyl head; can be saturated or unsaturated.

Saturated Fatty Acid

Fatty acid with no C=C double bonds; straight chains.

Unsaturated Fatty Acid

Fatty acid containing one or more C=C double bonds; kinks reduce packing and fluidity.

Triacylglycerol

Glycerol esterified to three fatty acids; the storage form of fatty acids in cells.

Phospholipid

Amphipathic lipids with two fatty acids and a polar head group bound to glycerol via a phosphate; main components of cell membranes.

Amphipathic

Molecule that has both hydrophilic and hydrophobic parts.

Amino Acid

Each has an amino group, a carboxyl group, and a side chain (R group); 20 standard amino acids.

Peptide Bond

Covalent bond formed between amino acids during protein synthesis via condensation; links amino acids in proteins.

Protein

A polymer of amino acids that folds into a functional 3D structure.

Nucleotide

Nucleoside with one or more phosphate groups; sugar is ribose or deoxyribose.

Nucleoside

A nitrogenous base attached to a five-carbon sugar without phosphate.

DNA

Polymer of nucleotides that stores genetic information.

RNA

Polymer of nucleotides involved in various roles in protein synthesis and gene expression.

mRNA

Carries genetic information from DNA to ribosomes to guide protein synthesis.

tRNA

Delivers specific amino acids to the ribosome during translation.

rRNA

Core component of ribosomes, essential for protein synthesis.

Phosphodiester Bond

Bond linking nucleotides in nucleic acids via sugar‑phosphate backbone (3' to 5' phosphate linkage).

ATP

Primary energy currency of the cell; hydrolysis releases usable energy.

Phosphoanhydride Bonds

High‑energy bonds in ATP and related molecules that release energy upon hydrolysis.

Coenzyme A (CoA)

A coenzyme that carries acyl groups for metabolism (important in fatty acid and energy metabolism).

cAMP

Cyclic adenosine monophosphate; a second messenger in intracellular signaling.

Covalent Bond

Bond formed by sharing electrons between atoms.

Ionic Bond

Bond formed by transfer of electrons, creating oppositely charged ions; weaker in solution due to solvent shielding.

Hydrogen Bond

A weak attraction between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom; important in water and biomolecule structure.

Van der Waals/Dispersion Force

Weak, noncovalent interactions due to transient fluctuations in electron density; contribute to molecular packing.

Hydrophobic Interaction

Tendency of nonpolar regions to associate in water to minimize disruption of water structure; not a true bond.

Beta
hyphen1,4 linkage

A type of glycosidic bond between glucose units in cellulose, formed by cellulose synthase.

Lipids

A diverse class of hydrophobic or amphipathic molecules important for energy storage, membranes, and signaling; not true polymers like carbohydrates or proteins.

Fatty Acid

A long hydrocarbon chain with a terminal carboxyl group; hydrophobic chain with hydrophilic carboxyl head; can be saturated or unsaturated.

Saturated Fatty Acid

Fatty acid with no C=C double bonds; straight chains.

Unsaturated Fatty Acid

Fatty acid containing one or more C=C double bonds; kinks reduce packing and fluidity.

Triacylglycerol

Glycerol esterified to three fatty acids; the storage form of fatty acids in cells.

Phospholipid

Amphipathic lipids with two fatty acids and a polar head group bound to glycerol via a phosphate; main components of cell membranes.

Amphipathic

Molecule that has both hydrophilic and hydrophobic parts.

Amino Acid

Monomers of proteins; each has an amino group, a carboxyl group, and a side chain (R group); 20 standard amino acids.

Peptide Bond

Covalent bond formed between amino acids during protein synthesis via condensation; links amino acids in proteins.

Protein

A polymer of amino acids that folds into a functional 3D structure.

Phosphodiester Bond

Bond linking nucleotides in nucleic acids via sugar
hyphenphosphate backbone (3' to 5' phosphate linkage).

Condensation Reaction

A reaction in which two molecules are covalently bonded through the loss of a water molecule

Hydrolysis

A reaction that breaks a covalent bond between two molecules by adding a water molecule.

Disaccharide

A sugar composed of two monosaccharides joined by a glycosidic bond.

Glycosidic Bond

A covalent bond formed between two monosaccharides by a dehydration reaction.

Enzyme

A protein that acts as a biological catalyst, speeding up chemical reactions without being consumed.

Denaturation

The process by which a protein loses its native 3D structure and consequently its biological activity, often due to changes in temperature, pH, or salinity.

Levels of Protein Structure

The four hierarchical structures of proteins: primary (amino acid sequence), secondary ($\alpha$ -helix, $\beta$ -pleated sheet), tertiary (overall 3D folding), and quaternary (multiple polypeptide chains).