189 - Ch 2 Molecules of Life

Vocabulary flashcards covering key Chapter 2 terms on atoms, bonds, water, pH, and the four major classes of biological molecules.

Acid

Substance that releases hydrogen ions (H⁺) in water, lowering pH.

Amino Acid

Protein monomer composed of a carboxyl group, an amine group, and one of 20 R-groups bonded to the same carbon.

Atomic Number

Number of protons in an atom’s nucleus; identifies the element.

ATP (Adenosine Triphosphate)

Energy-carrying nucleotide with adenine, ribose, and three phosphate groups; also an RNA monomer.

Base

Substance that accepts hydrogen ions in water, raising pH.

Buffer

Chemical set that stabilizes pH by alternately donating or accepting H⁺ or OH⁻ ions.

Carbohydrate

Organic molecule (CH₂O)n; includes monosaccharides, disaccharides, and polysaccharides.

Cellulose

Tough, insoluble glucose polysaccharide forming plant cell-wall structure.

Chemical Bond

Strong attractive force linking atoms in molecules (e.g., covalent, ionic).

Cohesion

Tendency of like molecules—especially water—to resist separation from each other.

Compound

Molecule composed of atoms of more than one element.

Concentration

Amount of solute per unit volume of solution.

Covalent Bond

Chemical bond in which two atoms share electron pairs.

Denaturation

Loss of a protein’s three-dimensional shape and function.

DNA (Deoxyribonucleic Acid)

Double-stranded nucleic acid of deoxyribose nucleotides; stores hereditary information.

Electron

Negatively charged subatomic particle orbiting an atomic nucleus.

Element

Pure substance consisting only of atoms with the same number of protons.

Evaporation

Transition of a liquid into vapor.

Fat (Triglyceride)

Lipid of three fatty acid tails bonded to glycerol.

Fatty Acid

Long hydrocarbon chain with hydrophilic carboxyl head and hydrophobic tail.

Free Radical

Atom or molecule with an unpaired electron; highly reactive.

Hydrogen Bond

Weak attraction between a covalently bonded H and another electronegative atom.

Hydrophilic

Describes substances that dissolve easily in water.

Hydrophobic

Describes substances that resist dissolving in water.

Ion

Atom or molecule carrying a net electric charge due to electron gain or loss.

Ionic Bond

Mutual attraction between oppositely charged ions.

Isotope

Variant of an element differing in neutron number (and thus mass).

Lipid

Fatty, oily, or waxy organic compound such as triglyceride, steroid, or wax.

Lipid Bilayer

Double layer of phospholipids forming the structural basis of cell membranes.

Mass Number

Total number of protons plus neutrons in nucleus

Metabolism

All enzyme-mediated chemical reactions occurring in a cell.

Monomer

Small subunit used to build polymers.

Neutron

Uncharged subatomic particle in the atomic nucleus.

Nucleic Acid

Polymer of nucleotides; DNA or RNA.

Nucleotide

Organic molecule of sugar, nitrogen base, and one to three phosphate groups.

Nucleus (Atomic)

Dense center of an atom containing protons and neutrons.

Organic Compound

Molecule composed mainly of carbon and hydrogen atoms.

Peptide Bond

Covalent bond joining the amine of one amino acid to the carboxyl of another.

pH

Measure of hydrogen-ion concentration in a solution.

Phospholipid

Lipid with two fatty acid tails and a phosphate-containing head; main membrane component.

Polarity

Separation of electric charge into positive and negative regions in a molecule.

Polymer

Molecule consisting of many monomers linked together.

Prion

Infectious, misfolded protein that damages nervous tissue.

Protein

Organic molecule of one or more folded amino acid chains.

Proton

Positively charged subatomic particle in the nucleus.

Reaction (Chemical)

Process leading to molecular change; making or breaking chemical bonds.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid of ribose nucleotides; functions in protein synthesis.

Salt

Ionically bonded compound that releases ions other than H⁺ or OH⁻ in water.

Saturated Fat

Triglyceride whose three fatty acid tails are fully saturated with single bonds.

Saturated Fatty Acid

Fatty acid with only single bonds in its hydrocarbon tail.

Shell Model

Diagram showing electron distribution in energy levels around an atom.

Solute

Substance that is dissolved in a solvent.

Solution

Uniform mixture of one or more solutes completely dissolved in a solvent.

Solvent

Substance, usually a liquid, that dissolves other substances.

Steroid

Lipid with four fused carbon rings and no fatty acid tails (e.g., cholesterol).

Temperature

Measure of the average kinetic energy (motion) of molecules.

Triglyceride

Fat molecule with three fatty acid tails linked to a glycerol backbone.

Unsaturated Fat

Triglyceride containing one or more unsaturated fatty acid tails; liquid at room temperature.

Unsaturated Fatty Acid

Fatty acid with at least one carbon–carbon double bond in its tail.

Wax

Firm, water-repellent lipid mixture forming protective layers in plants and animals.

complex lipid structure

octet rule

electron config 2,8,8

Dehydration Synthesis (Condensation)

Reaction that joins monomers into polymers while releasing a molecule of water.

Hydrolysis

Reaction that breaks polymers into monomers by adding water.

Monosaccharide

Single-sugar carbohydrate monomer (e.g., glucose).

Disaccharide

Carbohydrate consisting of two covalently bonded monosaccharides (e.g., sucrose).

Oligosaccharide

Carbohydrate made of a few (3–9) monosaccharides, often attached to lipids or proteins.

Polysaccharide

Carbohydrate polymer of many monosaccharides linked together.

Starch

Plant storage polysaccharide of coiled glucose chains.

Glycogen

Branched glucose polysaccharide that serves as energy storage in animals.

organic molecules

molecules made of mainly carbon and hydrogen

protein confirmation

only able to function if correct 3D structure is used

protein primary structure

The sequence of amino acids in a polypeptide chain that determines its properties and function.

protein secondary structure

primary structure folds into helical, sheet-like structures, stabilized by hydrogen bonds.

protein tertiary structure

sheets and helices fold forming 3D structures

quaternary structure

multiple chains associate to form a functional protein complex.

nucleotides

organic molecules act as enzyme helpers, chemical messengers, subunits of DNA/RNA
composed of phosphate group, 5 carbon group and nitrogen base