cytoskeleton and molecular motors

cytoskeleton

network of protein fibers in the cytoplasm

cytoskeleton components

microtubules, microfilaments (actin), intermediate filaments

microtubules are made of

tubulin and dimer

microtubules form how many protofilaments?

13

plus end of microtubule

rapid assembly/disassembly

minus end of microtubule

relatively stable; capped

microtubule instability examples

interphase, mitosis,

centrosome

microtubule organizing center of the cell

plus ends of microtubules are near the

plasma membrane

minus ends of microtubules are near

the nucleus

microtubules contain how many centrioles?

2

centrioles are

2 bundles of microtubules arranged at right angles

each centriole bundle is composed of

9 triplet microtubules arranged in a ring

microtubule molecular motors

dynein and kinesin

dynein

minus end directed motor

kinesin

plus end directed motor

cytoplasmic streaming

vesicles and organelles are moved around the cytoplasm by the microtubule molecular motors

flagella are made of

microtubules

cilia structure

9 outer doublet MTs 2 central singlet MT

dynein arms

hydrolyze ATP producing a whip like movement for the cilia

actin microfilaments

form a network of fibers throughout the cytoplasm

actin microfilament motility

myosin molecular motors provide movement

g-actin

forms fine microfilaments

actin is made up of

g-actin monomers, assembled into f-actin

plus end of actin

growth, ATP bound g-actin added

minus end of actin

shorten, ADP bound actin monomers are removed

pseudopodia

temporary extension of the cytoplasm

actin-related protein complexes

nucleate new actin filaments, pushing plasma membrane forward

listeria monocytogenes

intracellular bacterial parasite

what does listeria do

hijacks cellular actin polymerization system to propel itself through the cell

myosin moves by

walking on actin filaments

myosin functions

intracellular transport cargo, muscle contraction, cell motility

myosin motility

actin polymerization pushes leading edge of cell forward, myosin motors attached to the plasma membrane walk on bundles of actin filaments

intermediate filaments

large family of filaments that play many different structural roles in eukaryotic cells

intermediate filaments help

anchor cytoskeleton to extracellular matrix

types of intermediate filaments

keratin, nucelar lamins

keratin

intermediate filaments in skin cells

defective keratin causes

epidermolysis bullosa simplex

nuclear lamins

intermediate fibers of the nuclear lamina, supports nuclear envelope

nuclear lamina mutations cause

progeria, severe premature aging