3.1–3.4 Chemistry and Major Molecules of Life (Vocabulary Flashcards)

Vocabulary flashcards covering atoms, bonds, water properties, pH, nucleic acids, proteins, carbohydrates, lipids, and energy/enzymes as described in the lecture notes.

Atom

The basic unit of matter; composed of a nucleus containing protons and neutrons, with electrons orbiting around it.

Nucleus

The center of an atom where protons and neutrons are located.

Proton

A positively charged particle inside the nucleus.

Neutron

An electrically neutral particle inside the nucleus.

Electron

A negatively charged particle that orbits the nucleus and participates in bonding.

Atomic number

The number of protons in an atom's nucleus; identifies the element.

Isotope

Atoms of the same element with different numbers of neutrons.

2-8-8 rule

A simplified description of electron shells: 2 electrons in the first shell; 8 in the second and typically 8 in the third.

Molecule

Two or more atoms bonded together.

Compound

A substance made of two or more elements bonded together.

Covalent bond

Bond formed by sharing electrons between atoms.

Ionic bond

Bond formed by the transfer of electrons, creating oppositely charged ions.

Polar covalent bond

Covalent bond with unequal sharing of electrons, creating partial charges.

Nonpolar covalent bond

Covalent bond with equal sharing of electrons.

Water (H2O)

A polar molecule essential for life; acts as solvent and medium for reactions.

Polarity

Unequal distribution of electrical charge within a molecule.

Hydrogen bond

Weak attraction between a hydrogen atom and a highly electronegative atom (O, N, or F).

Cohesion

Attraction between water molecules, contributing to surface tension.

Adhesion

Attraction of water to surfaces, aiding capillary action.

pH

A scale (0–14) indicating how acidic or basic a solution is.

Acid

A substance that releases H+ ions in water.

Base

A substance that releases OH− or accepts H+ in water.

Nucleic acids

DNA and RNA; polymers built from nucleotides.

Nucleotides

Monomers of nucleic acids consisting of sugar, phosphate, and a nitrogenous base.

DNA

Deoxyribonucleic acid; stores genetic information; bases A, G, T, C; usually double-stranded.

RNA

Ribonucleic acid; uses A, G, C, U; sugar is ribose; often single-stranded.

Complementary base pairing

A pairs with T (or U in RNA); G pairs with C.

Amino acids

Building blocks of proteins; 20 standard amino acids linked by peptide bonds.

Protein

A biological macromolecule made of one or more polypeptides; functions depend on structure.

Primary structure

Linear sequence of amino acids in a protein.

Secondary structure

Local folds like alpha helices and beta sheets held together by hydrogen bonds.

Tertiary structure

Three-dimensional folding of a protein driven by R-group interactions.

Quaternary structure

Arrangement of multiple polypeptide subunits into a functional protein.

Carbohydrates

Organic molecules with C, H, O in a 1:2:1 ratio; includes monosaccharides, disaccharides, polysaccharides.

Monosaccharide

A single sugar unit (e.g., glucose).

Disaccharide

Two monosaccharides linked together.

Polysaccharide

Many monosaccharides linked together (e.g., starch, glycogen, cellulose).

Lipids

Molecules with high energy density; include triglycerides, phospholipids, steroids; 9 calories per gram.

Triglyceride

A lipid with three fatty acids attached to glycerol; primary fat storage.

Phospholipid

Lipid with a phosphate group; hydrophilic head and hydrophobic tail, forming membranes.

Steroid

Lipids with four fused rings (e.g., cholesterol, hormones like estrogen and testosterone).

Cholesterol

A steroid lipid that modulates membrane fluidity and precursor to steroids.

ATP

Adenosine triphosphate; primary energy currency of the cell; formed from ADP + Pi and energy.

ADP

Adenosine diphosphate; product of ATP losing a phosphate group; can be re-energized to ATP.

Enzyme

A protein catalyst that speeds up chemical reactions and is not consumed in the reaction.

Activation energy

The energy barrier that must be overcome for a reaction to proceed; lowered by enzymes.

Substrate

The reactant(s) that an enzyme acts upon.

Codon

A three-nucleotide sequence in mRNA that encodes a specific amino acid or stop signal.

Amino acid structure

Central carbon with an amino group, a carboxyl group, a hydrogen, and a variable side chain.

DNA base pairing (A–T/U and G–C)

A pairs with T in DNA (U in RNA); G pairs with C.

RNA base pairing (A–U and G–C)

A pairs with U in RNA; G pairs with C.