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- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/05%3A_DNA/5.06%3A_The_Meselson_-_Stahl_ExperimentThis page explains semiconservative DNA replication, where the two strands of DNA separate to serve as templates for new strands. Proposed by Watson and Crick and validated by the Meselson-Stahl exper...This page explains semiconservative DNA replication, where the two strands of DNA separate to serve as templates for new strands. Proposed by Watson and Crick and validated by the Meselson-Stahl experiment, this process ensures each daughter DNA molecule consists of one old and one new strand, resulting in an "immortal strand" passed through generations. This mechanism is observed in both bacteria such as E. coli and eukaryotic organisms during chromosome replication.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/09%3A_Regulation_of_Gene_Expression/9.02%3A_The_Tryptophan_RepressorThis page explains the regulation of tryptophan synthesis in E. coli, which involves five enzymes from a clustered operon. When tryptophan is abundant, it binds to the Trp repressor, a homodimer that ...This page explains the regulation of tryptophan synthesis in E. coli, which involves five enzymes from a clustered operon. When tryptophan is abundant, it binds to the Trp repressor, a homodimer that attaches to the operator of the operon, inhibiting transcription of the genes for enzyme production. This mechanism ensures that enzymes are not synthesized when tryptophan is already present, effectively regulating the metabolic pathway.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/03%3A_The_Cellular_Basis_of_Life/3.10%3A_The_ProteasomeThis page discusses the importance of protein degradation alongside synthesis, highlighting the roles of lysosomes and proteasomes. Lysosomes degrade extracellular proteins from endocytosis, while pro...This page discusses the importance of protein degradation alongside synthesis, highlighting the roles of lysosomes and proteasomes. Lysosomes degrade extracellular proteins from endocytosis, while proteasomes target intracellular proteins using a ubiquitin tagging system. This degradation process recycles amino acids and aids in antigen processing for immune response, involving complexes that present antigens to T cells.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/04%3A_Cell_Metabolism/4.10%3A_ChemiosmosisThis page discusses the chemiosmotic theory of ATP synthesis in chloroplasts, supported by observations that light illumination increases the alkalinity of the surrounding medium due to proton pumping...This page discusses the chemiosmotic theory of ATP synthesis in chloroplasts, supported by observations that light illumination increases the alkalinity of the surrounding medium due to proton pumping. It describes how altering the thylakoid pH by using acidic mediums allows chloroplasts to synthesize ATP in alkaline conditions with ADP and inorganic phosphate, showcasing the role of the proton gradient in ATP production even in the absence of light.
