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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Introduction Kinesins and dyneins are ATP-dependent molecular motors that move along microtubules. They convert the chemical energy of ATP hydrolysis into mechanical work and are essential for intracellular transport, organelle positioning, cell division, and cytoskeletal organization. The simplest distinction is: Kinesin → generally moves toward the microtubule plus endDynein → generally moves toward the microtubule minus end However, this is a useful generalization rather than an absolute rule: the kinesin superfamily contains motors with different directionalities, whereas dyneins are predominantly minus-end-directed. 2. Why Kinesin and Dynein Are Important Together, kinesin and dynein provide a major systemRead More →

Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Molecular motors are specialized proteins that convert the chemical energy of ATP hydrolysis into mechanical work. They move along cytoskeletal polymers or generate force within cytoskeletal networks. The three major families are: 2. Why Molecular Motors Are Important Cells are too large for many intracellular movements to occur efficiently by simple diffusion. Molecular motors provide: Thus, molecular motors function as the mechanochemical machinery of the cell. 3. General Architecture of Molecular Motors Many molecular motors contain three functional regions: 1. Motor domain Binds ATP and the cytoskeletal track. 2. Neck/stalk Transmits conformational changes. 3. Cargo-bindingRead More →

Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Intermediate filaments (IFs) are rope-like cytoskeletal polymers approximately 10 nm in diameter, intermediate in size between actin filaments (~7 nm) and microtubules (~25 nm). Their primary function is to provide mechanical strength, structural integrity and resistance to deformation. Unlike actin and microtubules, intermediate filaments are generally non-polar and do not function as conventional tracks for motor proteins. Major functions 2. The Three Cytoskeletal Systems Feature Actin Intermediate filaments Microtubules Diameter ~7 nm ~10 nm ~25 nm Basic unit Actin IF protein α/β-tubulin Polarity Polar Non-polar Polar Main function Movement/force Mechanical strength Transport/organization Motor proteins MyosinRead More →

Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Microtubules are cylindrical, polarized cytoskeletal polymers composed primarily of α-tubulin and β-tubulin heterodimers. They are approximately 25 nm in diameter and represent the largest of the three major cytoskeletal filament systems. Microtubules are essential for: 2. Three Major Cytoskeletal Systems Feature Actin Intermediate filaments Microtubules Diameter ~7 nm ~10 nm ~25 nm Basic unit Actin IF protein α/β-tubulin Polarity Yes Generally no Yes Major motor Myosin None Kinesin, dynein Major nucleotide ATP None directly GTP Major dynamic behavior Treadmilling Relatively stable Dynamic instability Major roles Movement/contraction Mechanical strength Transport/mitosis 3. Basic Structure A microtubule isRead More →

Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition The actin cytoskeleton is a dynamic network of actin filaments (microfilaments) distributed throughout the cytoplasm. It provides structural support and participates in: Unlike a static structural scaffold, the actin cytoskeleton is a highly dynamic, regulated system that continuously undergoes polymerization, depolymerization and remodeling. 2. Organization of the Cytoskeleton The cytoskeleton consists of three major filament systems: Component Approx. diameter Major function Actin filaments ~7 nm Cell shape, movement, contraction Intermediate filaments ~10 nm Mechanical strength Microtubules ~25 nm Intracellular transport, mitosis 3. Actin Structure Actin exists in two major forms: G-actin Globular actin A solubleRead More →