Chapter 10: Relationship between Cell Biology and Biochemistry

The plasma membrane is presented as a dynamic fluid mosaic structure composed of phospholipids, cholesterol, and embedded proteins that regulate selective passage of substances through mechanisms including simple diffusion, facilitated diffusion, active transport via Na⁺/K⁺-ATPase pumps, and vesicular pathways such as endocytosis and exocytosis. The glycocalyx layer, formed from carbohydrate moieties attached to proteins and lipids, functions in cell recognition and communication. The chapter systematically examines organelle-specific biochemistry: mitochondria generate adenosine triphosphate through oxidative phosphorylation and contain maternally inherited genetic material; lysosomes compartmentalize hydrolytic enzymes for macromolecule degradation, with dysfunction causing storage diseases including Tay-Sachs and Pompe disease; peroxisomes catalyze fatty acid oxidation and plasmalogen synthesis, with deficiencies producing disorders such as Zellweger syndrome. The cytoskeleton, comprising actin filaments, tubulin-based microtubules, and intermediate filaments, provides mechanical support, organizes intracellular space, and facilitates vesicle movement, while dystrophin mutations exemplify how cytoskeletal abnormalities manifest clinically. The nucleus houses chromatin-organized DNA and regulates gene expression through nuclear pore-mediated transport. The chapter integrates clinical examples demonstrating how disrupted cell biology causes disease: cholera toxin dysregulates chloride transport, colchicine microtubule disruption triggers acute gout symptoms, and acetaldehyde toxicity from chronic alcohol consumption impairs mitochondrial function and causes hepatic lipid accumulation. The endoplasmic reticulum and Golgi apparatus coordinate protein synthesis and lipid processing with subsequent posttranslational modifications and trafficking. By contrasting prokaryotic cells lacking membrane-bound organelles with their eukaryotic counterparts, the chapter emphasizes how cellular compartmentation enables the biochemical sophistication characteristic of higher organisms.