Quiz 03: Hydrocarbons, Functional Groups, and Lipids

Vocabulary flashcards derived from the lecture notes on hydrocarbons, functional groups, and lipids.

Hydrocarbon

Molecule composed of carbon and hydrogen; can differ in length, branching, number/position of carbon–carbon double bonds, and presence or absence of rings.

Hydrogen bond

A weak attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Functional group

A specific group of atoms within a molecule that determines its characteristic chemical reactions.

Hydroxyl group

An -OH group; polar and capable of hydrogen bonding; common in alcohols and sugars.

Carbonyl group

A C=O functional group; present in aldehydes and ketones.

Aldehyde

A carbonyl group at the end of a carbon skeleton.

Ketone

A carbonyl group within the carbon skeleton (not at the end).

Carboxyl group

-COOH; acidic group that can lose a proton to form -COO⁻.

Amino group

-NH₂; acts as a base and can be protonated to -NH₃⁺.

Sulfhydryl group

-SH; can form disulfide bonds (S–S) in proteins; relatively reactive.

Phosphate group

-OPO₃²⁻; acidic and versatile in energy transfer and signaling; can be protonated/deprotonated.

Methyl group

-CH₃; nonpolar group that increases hydrophobicity and often participates in limited reactions.

Polar

Describes a molecule with uneven charge distribution, leading to hydrophilicity and hydrogen bonding potential.

Nonpolar

Describes a molecule lacking significant charge separation; hydrophobic and poorly soluble in water.

Ionic state

Charged form of a functional group resulting from gain or loss of electrons (protonation/deprotonation).

Protonated state

Form in which a group has gained a proton, often carrying a positive charge (e.g., -NH₃⁺).

Deprotonated state

Form after loss of a proton, often carrying a negative charge (e.g., -COO⁻).

Conjugate base

The species that remains after an acid donates a proton; e.g., carboxylate or amine bases.

Amphipathic

Molecule with both hydrophilic and hydrophobic regions; enables membrane formation.

Lipid

A class of hydrophobic biological molecules including fats, oils, phospholipids, and steroids.

Phospholipid

Lipid with two fatty acids and a polar head; amphipathic; core component of cell membranes.

Sterol

Lipid with four fused carbon rings; includes cholesterol and steroid hormones.

Testosterone

A steroid hormone derived from cholesterol; an example of a sterol-derived molecule.

Fatty acid

Carboxylic acid with a long hydrocarbon chain; can be saturated or unsaturated; building block of lipids.

Glycerol

Three-carbon alcohol to which fatty acids are esterified in triglycerides and phospholipids.

Ester linkage

Covalent bond formed between a fatty acid and glycerol via a dehydration reaction.

Triglyceride

Glycerol with three fatty acids esterified; primary storage lipid in animals.

Melting temperature

Temperature at which a fat/lat lipid melts; increases with chain length and saturation, decreases with unsaturation.

Saturated

Fatty acids with only single C–C bonds; pack tightly; generally higher melting temperatures.

Unsaturated

Fatty acids containing one or more C=C bonds; kinked chains; generally lower melting temperatures.

Cis

Geometric isomer with substituents on the same side of a double bond; causes a bend in the molecule.

Trans

Geometric isomer with substituents on opposite sides of a double bond; usually straighter and higher melting point.

Trans double bond

A C=C double bond with substituents on opposite sides; associated with higher melting temperatures.

Lipid bilayer

Two-layered arrangement of phospholipids in aqueous solution; fundamental structure of cell membranes.

Micelle

Spherical assembly of amphipathic lipids in water; hydrophobic tails inward, heads outward.