Cell Biology Chapter 14

Question 1

Motors for MTs and MFs

Answer 1

Nearly all kinesins transport cargo toward the (+) end of microtubules (anterograde transport); Nearly all dyneins transport cargo toward the (−) end (retrograde transport); Anterograde refers to movement in the forward direction; In the context of vesicular trafficking: 1. movement from the site of protein synthesis in the rough endoplasmic reticulum (RER) towards the Golgi and then; 2. movement from the Golgi towards the final destination in the cell; The Golgi complex is actively clustered near the MTOC by movement on microtubules (near the – end); The ER extends along the microtubule network towards the (+) end periphery; Microtubules - ends are located near the Golgi and transport towards it from any part of the cell, including the RER, requires the - end directed motor dynein; Anterograde transport from the Golgi to a specific destination in the cell, or through the secretory pathway, requires the + end directed motor kinesin; Retrograde transport from the Golgi back to the ER would also use kinesin; Microfilament Motor Protein: Myosin walks to (+) end of microfilament; Myosins function in a wide range of cellular events, including: Muscle contraction, Cell movement, Phagocytosis, Vesicle transport; The basic function of myosin II is to pull arrays of actin filaments together, resulting in contraction of a cell or group of cells

Question 2

Mechanisms for movement and direction

Answer 2

Cell motility involves: Movement of a cell or organism through the environment; Movement of components in the cell; Kinesin movement looks like “walking,” with the two globular head domains taking turns as the front foot; It can move long distances along an MT before detaching from it by releasing bound ADP and acquiring a new ATP, so that the cycle repeats; Motor protein also uses ATP to drive conformational changes leading to mechanical movement; Stalks attach to MT, Intermediate and Light chains attach to cargo via dynactin complex proteins

Question 3

Muscle contraction mechanisms

Answer 3

 Contractility is used to describe shortening of muscle cells, is a specialized form of motility