Protein Folding, Bonds & Nucleic Acid Structure – Key Vocabulary

Comprehensive set of vocabulary flashcards covering protein structure, bonding, nucleic acids and DNA replication concepts discussed in the lecture.

Peptide Bond

Strong covalent bond that links amino acids together in the primary structure of proteins.

Primary Structure (Protein)

Linear sequence of amino acids in a polypeptide chain.

Secondary Structure (Protein)

Local folding of a polypeptide into α-helices or β-pleated sheets via hydrogen bonds between backbone groups.

α-Helix

Coiled secondary structure of a protein stabilized by hydrogen bonds; resembles a spring.

β-Pleated Sheet

Sheet-like secondary structure formed when strands of polypeptide align side-by-side with hydrogen bonding.

Tertiary Structure (Protein)

Overall three-dimensional folding of a single polypeptide stabilized by interactions among R-groups (hydrophobic, ionic, disulfide, H-bonds).

Quaternary Structure

Assembly of two or more tertiary subunits into a functional protein complex (e.g., hemoglobin).

Denaturation

Unfolding of a protein’s 3-D structure due to pH, temperature or other environmental changes.

R Group (Side Chain)

Variable part of an amino acid that determines its chemical properties and influences folding.

Hydrophobic Interaction

Non-polar side chains avoiding water, driving parts of a protein to fold inward.

Disulfide Bond

Strong covalent S-S bond between two cysteine residues; locks tertiary structure in place.

Ionic Bond (in proteins)

Attraction between oppositely charged side chains that helps stabilize tertiary structure.

Hemoglobin

Tetrameric blood protein that transports oxygen; composed of two α and two β subunits.

Sickle-Cell Anemia

Disease caused by a single amino-acid substitution (Glu→Val) in hemoglobin, producing sickle-shaped red cells.

Ribosome

Ribonucleoprotein machine that translates mRNA into the primary structure of proteins.

Polymer

Macromolecule made of repeating identical or similar monomers (e.g., proteins, carbohydrates, nucleic acids).

Glycosidic Bond

Covalent linkage joining monosaccharides in carbohydrates.

Ester Linkage

Bond connecting glycerol to fatty acid chains in lipids; reason lipids are not true polymers.

Nucleotide

Monomer of nucleic acids consisting of a phosphate group, five-carbon sugar, and nitrogenous base.

Phosphate Group

Negatively charged functional group that forms part of the nucleotide backbone and stores energy in ATP.

Pentose Sugar

Five-carbon sugar in nucleotides: ribose in RNA, deoxyribose in DNA.

Ribose

Sugar in RNA containing a hydroxyl group on the 2′ carbon.

Deoxyribose

Sugar in DNA lacking the 2′-carbon oxygen; makes DNA less reactive.

Purine

Double-ring nitrogenous base; adenine (A) or guanine (G).

Pyrimidine

Single-ring nitrogenous base; cytosine (C), thymine (T), or uracil (U).

Phosphodiester Linkage

Covalent bond joining nucleotides between the 3′-OH of one sugar and the 5′-phosphate of the next.

Antiparallel

Orientation of the two strands in DNA running 5′→3′ in opposite directions.

Complementary Base Pairing

Specific hydrogen bonding of A with T (or U) and C with G in nucleic acids.

ATP (Adenosine Triphosphate)

High-energy nucleotide with three phosphates; hydrolysis releases energy for cellular work.

Supercoiling

Tight twisting of DNA to compact it before wrapping around histone proteins.

Histone

Positively charged protein spool around which DNA winds to form nucleosomes and chromosomes.

Semi-Conservative Replication

DNA duplication mechanism where each new double helix contains one parental and one new strand.

Dimer

Quaternary protein composed of two subunits; may be homo- or hetero-dimeric.

Tetramer

Protein complex made of four subunits, such as hemoglobin.

Watson & Crick

Scientists who proposed the double-helix model and base-pairing rules of DNA (using Franklin’s X-ray data).

Rosalind Franklin

Researcher whose X-ray crystallography images provided critical evidence for DNA’s helical structure.