Lecture 3 Vocab

5’ phosphate

The phosphate group attached to the 5’ carbon of a nucleotide’s sugar; important for DNA/RNA strand directionality.

3’ hydroxyl

The hydroxyl (-OH) group attached to the 3’ carbon of a nucleotide’s sugar; site of new nucleotide addition.

Adenine

A purine nitrogenous base in DNA and RNA that pairs with thymine (DNA) or uracil (RNA).

Alpha glycosidic bond

A covalent bond between two monosaccharides with the OH group of the first carbon in the alpha orientation.

Alpha helix

A common protein secondary structure where the chain coils into a right-handed spiral stabilized by hydrogen bonds.

Amino acid

The building block of proteins, consisting of an amino group, a carboxyl group, a hydrogen atom, and a variable side chain.

Antiparallel

Refers to the opposite 5’→3’ orientations of the two strands in a DNA double helix.

Beta glycosidic bond

A covalent bond between monosaccharides where the OH group on the first carbon is in the beta orientation.

Beta (pleated) sheet

A protein secondary structure formed by hydrogen bonding between parallel or antiparallel strands.

Biological membrane

A lipid bilayer with embedded proteins that forms the boundary of cells and organelles.

Carbohydrate

Organic molecules made of monosaccharides; serve as energy sources and structural components.

Chiral carbon

A carbon atom bonded to four different groups, giving rise to stereoisomers.

Cis-unsaturated

A fatty acid with a double bond causing a bend in the chain due to hydrogen atoms on the same side.

Cytosine

A pyrimidine nitrogenous base in DNA and RNA that pairs with guanine.

Dehydration synthesis

A chemical reaction that joins monomers by removing water; forms bonds like peptide and glycosidic bonds.

Deoxyribose

A five-carbon sugar in DNA lacking a hydroxyl on the 2’ carbon.

Double helix

The twisted ladder-like structure of DNA formed by two antiparallel strands held by base-pair hydrogen bonds.

Ester bond

A covalent bond formed between a hydroxyl group and a carboxyl group, common in fats.

Fatty acid

A hydrocarbon chain with a terminal carboxyl group; building block of lipids.

Guanine

A purine nitrogenous base in DNA and RNA that pairs with cytosine.

Hydrolysis

A reaction that breaks covalent bonds by adding water; opposite of dehydration synthesis.

Lipid raft

A microdomain in membranes rich in cholesterol and sphingolipids that organizes signaling molecules.

Nucleotide

Monomer of nucleic acids, made of a sugar, phosphate group, and nitrogenous base.

Peptide bond

A covalent bond connecting amino acids in proteins, formed by dehydration synthesis between carboxyl and amino groups.

Phosphodiester bond

The linkage between nucleotides in nucleic acids, connecting the 3’ hydroxyl of one sugar to the 5’ phosphate of another.

Phospholipid

A lipid with a glycerol backbone, two fatty acids, and a phosphate group; key component of membranes.

Primary structure

The unique linear sequence of amino acids in a protein.

Purine

A nitrogenous base with a two-ring structure (adenine and guanine).

Pyrimidine

A nitrogenous base with a single-ring structure (cytosine, thymine, and uracil).

Ribose

A five-carbon sugar in RNA with a hydroxyl group on the 2’ carbon.

Saturated fatty acid

A fatty acid with no double bonds in its hydrocarbon chain; usually solid at room temperature.

Secondary structure

Local folding of a polypeptide chain into alpha helices or beta sheets stabilized by hydrogen bonds.

Side chain (R group)

The variable group attached to the alpha carbon of an amino acid; determines chemical properties.

Stereoisomer

Molecules with the same molecular formula and connectivity but different 3D orientations around a chiral carbon.

Tertiary structure

The overall 3D shape of a protein, determined by interactions between R groups.

Thymine

A pyrimidine nitrogenous base in DNA that pairs with adenine.

Trans-unsaturated

A fatty acid with a double bond where hydrogens are on opposite sides, creating a straighter chain.

Triglyceride

A lipid composed of glycerol and three fatty acids; main form of energy storage in animals.

Uracil

A pyrimidine nitrogenous base in RNA that pairs with adenine.