Cell Biology, Macromolecules, and DNA Replication

Vocabulary flashcards covering cellular biology, macromolecule structures, organelle evolution, nucleic acids, and DNA replication based on lecture summary points.

Central Dogma

The framework explaining how cells store genetic information in DNA, which is transcribed into RNA and translated into functional proteins.

Four Major Macromolecules

The four main biological molecules composed of monomeric subunits: Proteins, Nucleic Acids, Carbohydrates, and Fats/Membrane Lipids.

Condensation Reaction

A chemical reaction through which macromolecule polymers are synthesized; it is the reverse of a hydrolysis reaction.

Hydrolysis Reaction

A chemical reaction that breaks down macromolecule polymers into monomeric subunits; it is the reverse of a condensation reaction.

Three Domains of Life

The three primary classifications of living organisms: Bacteria (prokaryote), Archaea (prokaryote), and Eukaryotes.

Common Features of All Cells

The four basic structural components shared by all cell types: Plasma Membrane, Cytosol, DNA (Chromosomes), and Ribosomes.

Endosymbiotic Theory

The theory suggesting that eukaryotic organelles originated from prokaryotes, where the nucleus, ER, and Golgi arose from plasma membrane invagination, and mitochondria and chloroplasts arose from engulfed prokaryotic organisms.

Amino Acid

The monomeric subunit of proteins, consisting of a common core structure and a variable side chain ($R$ group) that dictates its specific properties.

Peptide Bond

The covalent bond that links amino acids together to form polypeptide chains.

Levels of Protein Structure

The four organizational levels of proteins: primary, secondary, tertiary, and quaternary, with quaternary structure occurring only in functional proteins composed of multiple polypeptide chains.

Chaperone Protein

A specialized protein within cells that assists other proteins in folding properly into their functional three-dimensional shapes.

Amyloids

Misfolded protein aggregates that cause cellular damage and lead to conditions such as prion diseases.

Disulfide Bond

A specific covalent bond formed between cysteine side chains that stabilizes protein tertiary and quaternary structures.

Nucleotide

The monomeric building block of nucleic acids, consisting of a phosphate group, a sugar (ribose or deoxyribose), and a nitrogenous base.

Phosphodiester Bond

The covalent linkage joining nucleotides together in nucleic acids by connecting the $3'$ carbon of one sugar to the $5'$ carbon of the next sugar.

DNA Double Helix

A right-handed double-helical structure composed of two antiparallel DNA strands held together by hydrogen bonding between complementary base pairs stacked perpendicular to the backbone axis.

Complementary Base Pairing

The specific hydrogen bonding pattern in DNA where Adenine joins with Thymine via $2$ hydrogen bonds, and Cytosine joins with Guanine via $3$ hydrogen bonds.

Histone Proteins

Positively charged, basic amino acid-rich proteins that bind to DNA to form nucleosomes, which further coil and condense to form compact chromosomes.

Nucleosome

The fundamental unit of eukaryotic DNA packaging, formed by DNA wrapped around histone proteins.

Semiconservative Replication

The model of DNA replication in which each resulting double-stranded DNA molecule consists of one original parental strand and one newly synthesized strand.

DNA Helicase

The enzyme that unwinds double-stranded DNA during replication by breaking the hydrogen bonds between complementary base pairs.

Topoisomerase

The enzyme that relieves tension from unwinding DNA ahead of the replication fork.

Single-Stranded Binding Proteins

Proteins that bind to and stabilize single-stranded DNA during replication to prevent re-annealing.

DNA Primase

The enzyme that synthesizes a short RNA primer onto single-stranded DNA to initiate elongation.

DNA Polymerase

The enzyme that elongates DNA strands by adding nucleotides to the free $3'\text{-OH}$ of an RNA primer in a strictly $5' \rightarrow 3'$ direction, which also possesses intrinsic proofreading activity.

Leading Strand

The newly synthesized DNA strand that is replicated continuously in the $5' \rightarrow 3'$ direction toward the replication fork.

Lagging Strand

The newly synthesized DNA strand that is replicated discontinuously away from the replication fork in short segments called Okazaki fragments.

Okazaki Fragments

Short, discontinuous segments of DNA synthesized on the lagging strand during DNA replication.

DNA Ligase

The enzyme that seals the sugar-phosphate backbone by joining Okazaki fragments together into a continuous DNA strand.

Rosalind Franklin

The scientist who contributed key evidence to solving the structure of DNA through X-ray diffraction photography.

Erwin Chargaff

The scientist who discovered base ratios in DNA, demonstrating that adenine equals thymine ($\text{A} = \text{T}$) and cytosine equals guanine ($\text{C} = \text{G}$).

Watson and Crick

The scientists who proposed the right-handed double-helix model of DNA in 1953 and hypothesized semiconservative replication.