a+p chapter 2

A comprehensive set of vocabulary flashcards covering the key concepts, terms, and definitions from Chapter 02: The Chemistry of Life.

Atom

The simplest unit of matter with unique chemical properties, composed of a nucleus of protons and neutrons surrounded by electrons.

Nucleus

The central part of an atom that contains protons and neutrons.

Proton

Positively charged subatomic particle with a mass of 1 atomic mass unit (amu) located in the nucleus.

Neutron

Electrically neutral subatomic particle with a mass of 1 amu located in the nucleus.

Electron

Negatively charged subatomic particle with very little mass, orbiting the nucleus in electron shells.

Atomic number

Number of protons in the nucleus; defines the identity of an element.

Atomic mass

Approximate total number of protons and neutrons in the nucleus; used to describe mass of an atom.

Isotope

Variants of an element that differ in the number of neutrons; same chemical behavior but different atomic mass.

Radioisotope

Unstable isotope that decays and emits radiation.

Ion

Charged particle (atom or molecule) with unequal numbers of protons and electrons.

Cation

Ion with a net positive charge due to loss of electrons.

Anion

Ion with a net negative charge due to gain of electrons.

Ionization

Transfer of electrons from one atom to another, producing ions.

Salt

Electrically neutral compound of cations and anions that dissociates in water to form ions (electrolytes).

Electrolyte

Substance that ionizes in water to produce solutions that conduct electric current; important for nerve and muscle function.

Free radical

Unstable, highly reactive atom or molecule with an unusual number of electrons.

Antioxidant

Chemicals that neutralize free radicals (e.g., SOD, vitamins C and E, selenium).

Molecule

Two or more atoms bonded together.

Compound

A molecule composed of two or more different elements.

Isomer

Molecules with the same molecular formula but different structural arrangements.

Ionic bond

Attraction between oppositely charged ions (e.g., Na+ and Cl−) forming compounds.

Covalent bond

Bond formed by sharing electron pairs between atoms.

Nonpolar covalent bond

Covalent bond in which electrons are shared equally (e.g., C–C, O=O).

Polar covalent bond

Covalent bond in which electrons are shared unequally (e.g., H–O).

Hydrogen bond

Weak attraction between a slightly positive hydrogen atom and a slightly negative atom (usually O or N) in another molecule.

Van der Waals forces

Weak, brief attractions between neutral atoms; contribute to molecular interactions and protein folding.

Water

Polarity and hydrogen bonding give water solvency, cohesion, adhesion, chemical reactivity, and thermal stability essential to life.

Solvent

The substance (often water) present in greatest amount in a solution; dissolves solutes.

Solute

Substance dissolved in a solvent.

Hydrophilic

Substances that readily interact with water; polar or charged.

Hydrophobic

Substances that do not interact well with water; nonpolar or neutral.

Hydration sphere

Water shell around ions or molecules in solution that stabilizes them.

Solubility

Ability of a substance to dissolve in a solvent.

pH

A measure of hydrogen ion concentration; pH

Acid

Substance that donates protons (H+) in water; lowers pH.

Base

Substance that accepts protons (H+) in water; raises pH.

Buffer

Solution that resists changes in pH by neutralizing added acids or bases.

Solution

Mixture where solute particles are dispersed evenly; solute particles are <1 nm and do not scatter light.

Colloid

Mixture with particle sizes 1–100 nm that scatter light and are usually cloudy; particles stay dispersed.

Suspension

Mixture with particles >100 nm that separate on standing; e.g., blood cells in plasma.

Molarity (M)

A measure of solute concentration: moles of solute per liter of solution.

Millimolar (mM)

One-thousandth of a mole per liter; common physiological concentration unit.

Milliequivalents per liter (mEq/L)

Concentration expressing electrolyte amount adjusted for electrical charge.

Dehydration synthesis (condensation)

Bond-forming reaction where monomers join and water is released.

Hydrolysis

Bond-breaking reaction where water is added to split polymers into monomers.

Carbohydrate

Hydrophilic organic molecules, usually with a C:H:O ratio; sugars and starches.

Monosaccharide

Simple sugar, the basic unit of carbohydrates (e.g., glucose, galactose, fructose).

Glucose

A six-carbon monosaccharide; blood sugar.

Disaccharide

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

Sucrose

Disaccharide of glucose and fructose; table sugar.

Lactose

Disaccharide of glucose and galactose; milk sugar.

Maltose

Disaccharide of two glucose units; malt sugar.

Polysaccharide

Many monosaccharides linked; storage or structural carbohydrates (e.g., glycogen, starch, cellulose).

Glycogen

Animal storage polysaccharide; stored in liver and muscles.

Starch

Plant storage polysaccharide digestible by humans.

Cellulose

Structural polysaccharide in plants; dietary fiber; indigestible by humans.

Lipid

Hydrophobic molecules with high hydrogen-to-oxygen ratio; energy-dense.

Fatty acid

Carboxyl-terminated hydrocarbon chain; may be saturated or unsaturated.

Saturated

Fatty acid with single C–C bonds; maximum hydrogen.

Unsaturated

Fatty acid with one or more C=C double bonds; can add hydrogen.

Triglyceride

Three fatty acids linked to glycerol; primary dietary fat and energy storage.

Phospholipid

Two fatty acids plus a phosphate group; amphipathic, major component of cell membranes.

Eicosanoid

20-carbon lipid signaling molecules derived from arachidonic acid (e.g., prostaglandins).

Steroid

Lipid with four-ring structure; includes cholesterol and hormones.

Cholesterol

Sterol lipid; component of cell membranes; precursor to steroids; HDL/LDL relate to cholesterol transport.

HDL (high-density lipoprotein)

“Good” cholesterol; transports cholesterol to liver for disposal.

LDL (low-density lipoprotein)

“Bad” cholesterol; can contribute to plaque buildup in arteries.

Protein

Polymer of amino acids that perform structural, catalytic, signaling, and transport roles.

Amino acid

Amino group, carboxyl group, and variable side chain (R); 20 standard amino acids.

Peptide

Two or more amino acids linked by peptide bonds.

Primary structure

Linear sequence of amino acids in a protein.

Secondary structure

Coiled or folded shapes (alpha helix, beta sheet) stabilized by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a protein due to hydrophobic, ionic, and disulfide interactions.

Quaternary structure

Association of two or more polypeptide chains in a protein complex (e.g., hemoglobin).

Conformation

Three-dimensional shape of a protein; crucial for function.

Denaturation

Unfolding of a protein’s structure due to heat, pH, or other agents; loss of function.

Prosthetic group

Non-amino acid moiety tightly bound to a protein (e.g., heme in hemoglobin).

Enzyme

Protein (or RNA) that acts as a biological catalyst to speed reactions.

Active site

Region of an enzyme where substrate binds.

Substrate

Reactant(s) that bind to an enzyme’s active site.

Cofactor

Nonprotein helper required by some enzymes; can be inorganic ion or organic molecule.

Coenzyme

Organic cofactor, often derived from vitamins (e.g., NAD+).

NAD+

Nicotinamide adenine dinucleotide; electron carrier in metabolism.

ATP

Adenosine triphosphate; main energy currency of the cell; energy stored in high-energy phosphate bonds.

ADP

Adenosine diphosphate; product of ATP hydrolysis with release of energy.

Phosphorylation

Addition of a phosphate group to a molecule, often activating it.

Glycolysis

Glucose breakdown in cytoplasm to pyruvate with a small amount of ATP produced.

Pyruvate

End product of glycolysis; fate depends on oxygen availability.

Aerobic respiration

Metabolic pathway in mitochondria that uses oxygen to produce ATP from glucose.

Anaerobic fermentation

ATP-producing pathway that occurs without oxygen; produces lactate or ethanol.

GTP

Guanosine triphosphate; energy source in certain reactions.

cAMP

Cyclic adenosine monophosphate; second messenger in cellular signaling.

DNA

Deoxyribonucleic acid; genetic material that stores instructions for protein synthesis.

RNA

Ribonucleic acid; translates genetic information to synthesize proteins.

Nucleotides

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

Nucleic acids

Macromolecules (DNA and RNA) made of nucleotides that store and express genetic information.

Oxidation

Loss of electrons; often releases energy in metabolic reactions.

Reduction

Gain of electrons; often stores energy in metabolic reactions.

Metabolism

All chemical reactions in the body; includes catabolism and anabolism.

Catabolism

Energy-releasing breakdown of molecules; provides building blocks and energy.