L25 - Cell movement (intro)

overview

movement inside cells: dynamic instability of MTs

movement outside cells: MTs + dyneins inside cilia on airway cells

Diffusion

= movement of molecules from [high] → [low]

• ions & proteins

ex. lateral diffusion of new phospholipids from ER to nuclear envelope

note: takes around 15s for a phospholipid to travel round a nucleus (2micrometer/sec)

Membrane Transport Proteins

= proteins that move molecules across a membrane

ex. GLUT (glucose it too large to fit thru a channel)

Receptor Proteins

= deliver cargo to target organelles

ex. M6P receptors deliver lysosome proteins (enzymes) from Golgi → lysosome

Protein Assembly

= formation of large protein complexes → causes movement

ex. assembly of clathrin (coat proteins) during RME shapes membrane

ex. growing MTs push against plasma membrane

Protein Disassembly

= disassembly of large protein complexes → get movement

ex. shrinking MTs during anaphase - pulls chromosome to centrosome

Water Pressure

= water enters → increased water pressure causes expansion of cell

• used by plants (venus fly trap & squirting cucumber)

Single Motor Proteins

• walk vesicles along cytoskeleton

→ cytoskeleton DOESNT move

cytoplasmic streaming in plant cells is done with myosin walking to the ___ end of F-actins

plus end

(single motor protein example)

Motor Protein Bundles

= double-headed motor proteins attached at their tails

→ cytoskeleton MOVES

ex. myosin - both move twd the (+) end

ex. Contractile Bundles (F-actin + myosin) = do cytokinesis of animal cells

ex. Extension Bundles (Mts + kinesins) = elongate animals cells during anaphase

Examinable content

diffusion: lateral diffusion of new phospholipids to nuclear envelope

protein assembly:

protein disassembly:

water pressure:

single motor proteins:

motor protein bundles:

• contractile bundles

  

• extension bundles