Consider this chart of engineered large-scale structures and their molecular counterparts. This may give you an idea of the molecular shapes that allow molecules to work in their dynamic 3-D world.

Technology	Function	Molecular example(s)
Struts, beams, crosslinks *	Transmit force Reinforce	Microtubules, cellulose, mineral casings
Cables	Transmit tension	Collagen
Gears* *	Conformation-changing protein actuators, moving things	Actin and myosin; see molecular gear
Motors	Turn shafts	Flagellar motor
Containers, packaging	Hold fluids, ingredients for catalysis	Lipid vesicles
Pipes	Carry fluids	Various tubular structures
Pumps	Move fluids and ions	Membrane proteins that pump ions and molecules
Conveyor belts	Move components	RNA moved by fixed ribosome (partial analog)
Clamps	Hold workpieces	Enzymatic binding sites
Hinges	Join units flexibly*	Enzymatic binding sites
Measure	Determine size	Enzymatic function
Cutters	Cut into pieces	Enzymatic role e.g., Lysosyme
Bearings	Smooth motion	molecular bearings.

Source: Adapted from K. Eric Drexler , Molecular engineering:An approach to the development of general capabilities for molecular manipulationProceedings of the National Academy of Sciences, USA. Vol. 78, No. 9, pp. 5275-5278, September 1981 [ PERMISSION PENDING] See http://www.imm.org/PNAS.html

Go On to explore molecules.

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