Biology Notes Flashcards: Chemistry of Life and Macromolecules

Vocabulary flashcards covering essential elements, bonding, water properties, carbohydrates, lipids, proteins, and functional groups.

Element

A basic substance that cannot be broken down into simpler substances by chemical means; life uses about 25 essential elements.

Covalent bond

A chemical bond formed by sharing electrons between atoms; can be nonpolar or polar.

Ionic bond

Electrostatic attraction between oppositely charged ions.

Nonpolar covalent bond

Covalent bond where electrons are shared equally, often between atoms with similar electronegativities (e.g., CH4).

Polar covalent bond

Covalent bond where electrons are not shared equally, creating partial charges (e.g., O–H in water).

Hydrogen bond

Weak attraction between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom.

Cohesion

Attraction between like molecules, such as water–water.

Adhesion

Attraction between unlike substances, such as water to the walls of a tube.

Capillary action

Movement of water up narrow tubes due to cohesion and adhesion.

Solvent

A substance (like water) that dissolves solutes; water is a versatile biological solvent.

Hydration shell

Sphere of water molecules surrounding a dissolved ion or molecule.

Hydrophobic

Water-fearing; molecules that do not interact well with water (usually nonpolar).

Monomer

A small molecule that can join with others to form a polymer.

Polymer

A large molecule composed of many monomer units covalently bonded together.

Dehydration synthesis

Condensation reaction that forms a covalent bond between monomers with release of water.

Hydrolysis

Reaction that breaks covalent bonds by adding water, yielding smaller molecules.

Carbohydrate

Biomolecule class including sugars and their polymers; main source of energy.

Monosaccharide

Simple sugar; basic unit of carbohydrates (e.g., glucose, fructose, ribose).

Disaccharide

Two monosaccharides linked by a condensation reaction (e.g., sucrose).

Polysaccharide

Polymer of monosaccharides; includes starch, glycogen, cellulose.

Glucose

C6H12O6; a monosaccharide; isomer of fructose and galactose.

Fructose

Monosaccharide isomer of glucose.

Galactose

Monosaccharide isomer of glucose.

Sucrose

Disaccharide; glucose + fructose; major transport sugar in plants.

Starch

Plant storage polysaccharide made of glucose; includes amylose (unbranched) and amylopectin (branched).

Amylose

Unbranched form of starch forming a helix.

Amylopectin

Branched form of starch.

Glycogen

Animal storage polysaccharide; highly branched glucose polymer.

Alpha glucose

Glucose ring form used in starch; forms helical polymers.

Beta glucose

Glucose ring form used in cellulose; forms straight chains.

Cellulose

Structural polysaccharide in plant cell walls; made from beta glucose; forms microfibrils.

Glycerol

Three-carbon backbone with a hydroxyl group on each carbon; part of lipids.

Fatty acid

Carboxyl group attached to a long hydrocarbon chain; length and saturation vary.

Saturated fatty acid

No carbon–carbon double bonds; straight chain; typically solid at room temperature.

Unsaturated fatty acid

One or more double bonds; kinked chain; typically liquid at room temperature.

Phospholipid

Lipid with two fatty acids, a glycerol backbone, and a phosphate group; hydrophobic tails and hydrophilic head.

Steroid

Lipid with four fused carbon rings; cholesterol is a key example.

Cholesterol

Essential membrane component and precursor to other steroids; high levels linked to cardiovascular risk.

Testosterone

A steroid hormone; structural differences from estradiol due to different functional groups.

Estradiol

A steroid hormone; functional groups lead to distinct biological activity.

Amino acid

Building block of proteins; central carbon with an amino group, a carboxyl group, a hydrogen, and an R group.

R group (side chain)

Variable side chain that determines the properties of an amino acid.

Peptide bond

Covalent bond linking amino acids via dehydration synthesis.

Primary structure

Unique sequence of amino acids in a protein.

Secondary structure

Regular folding patterns (alpha helices and beta pleated sheets) due to backbone hydrogen bonds.

Tertiary structure

Overall three-dimensional shape resulting from interactions among R groups.

Quaternary structure

Assembly of multiple polypeptide subunits in a protein.

Enantiomer

Mirror-image isomer; molecules with four different substituents can exist as left- and right-handed forms.

Thalidomide enantiomers

Different enantiomers can have drastically different biological effects; shape matters.

Functional group

Specific group of atoms that participates in chemical reactions and influences molecule properties.

Carboxyl group

-COOH; acidic functional group found in organic acids and amino acids.

Amino group

-NH2; basic functional group found in amino acids and amines.

Phosphate group

-OPO3^2-; important for energy transfer (ATP) and in nucleic acids.

Hydration shell

Layer of water molecules surrounding a dissolved ion or polar molecule.

N-O-S bridge

A newly observed crosslink in proteins involving nitrogen–oxygen–sulfur atoms.

Protein

Macromolecule made of amino acids; performs catalysis, structure, signaling, transport, and defense.