Lecture 6 Notes - Molecule Shape
Lecture 6 Notes - Molecule Shape BIL 255
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This 3 page Class Notes was uploaded by Elizabeth Mompoint on Tuesday September 22, 2015. The Class Notes belongs to BIL 255 at University of Miami taught by Dr. Mallery in Fall 2015. Since its upload, it has received 18 views. For similar materials see Cellular & Molecular Biology in Biology at University of Miami.
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Date Created: 09/22/15
Cell and Molecular Biology Lecture 6 The Shapes of Biomolecules Biological work entails among others mechanical functions biosynthesis transport electrophysiology amp homeostasis all of which depend upon the shape of molecules Structural chemistry 3Dmolecular shape is dependent upon the orientation of covalent bonds in space Molecular configuration results in specific bond angles amp molecular geometry a Methane H lHECEH H L isomer levorotatory rotates plane of polarized lightto the left tetrahedron free rotation bl Formaldehyde flat plane no free rotation D isomer Shape Ballandstick model IChemical structure Spacefilllng model dlext rorotatory rotates plane or polarized light to the light Stereoisomers two molecules which have identical composition but are not equivalent as they have 2 molecular orientations in space or are mirror images 0 Levorotary L or S rotates light left negative optical rotation O Dextrorotatory D or R rotates light right positive optical rotation O Often have different biological activity ie L Dopa vs DDopa Chiral molecules are superimposable on its mirror image as human hands Enantiomers are not superimposable on its mirror image Biological Activity Biological activity is the catalytic ability of molecules to do work There are 2 properties of biomolecules which contribute to a molecules unique fitness for Biological Activity amp the Living State 1 Configuration the permanent geometry that results from the spatial arrangement of an atom s bonds the spatial arrangement of atoms via bonds in the molecule cannot be interconverted without breaking bonds at Glucose vs galactose are examples of isomers based on covalent bond configurations each has different chemical and biological properties b Isomers built upon planar double bonds fix atoms above amp below plane of molecule amp restricts free rotation thereby fixing 3D shape in space i maleic cis vs fumaric trans llcisretinal vs 11 transretinal 2 Conformation or shape surface outline or contour of molecules a 3D orientation of chemical groups that are free to assume different positions in space without breaking any bonds i Due primarily to free rotation of atoms about a single chemical bond amp weak noncovalent forces that hold atoms in spatial arrays ii Consequences of conformations different conformational shapes forms of molecules can exist only one of which may be biologically active the other conforms aren39t b Enzymes can distinguish between biologically active forms conforms based upon the quotshapequot of that molecule 0 Biological Design A basic question of the living condition has always been How do individual groups of molecules assemble themselves into living organisms One sees recurring patterns of spirals triangulated forms amp pentagons in everything from molecules to viruses to plant owers Is there some universal principle of molecular selfassembly O Molecules join to form larger amp more stable structures often with new and emergent properties macromolecules gt organelles gt cells gt tissues gt organs Tensegrity tensional integrity when a structure maintains stability under tension it may be an architectural principle that helps contributes to biological form 0 Defines mechanical rules of how structures are stabilized by balancing forces of internal tension and compression Geodesic Domes an entire structure distributes its mechanical stresses frames of rigid struts connected into triangles squares pentagons or heptagons each of which balances compression and tension do not touch each other while tensioned wires delineate them spatially I Bucky Ball fullerene Prestress Structures struts that bear compression are distinct from wires bearing tension Compression members can provide rigidity while remaining separate not touching one another held in stasis only by means of tensed wires At the organismal level bones are the compression struts and muscles tendons amp ligaments are the tension bearing wires I Cytoskeletal elements as the microtubules may act as compression quotgirdersquot and microfilaments may exert tension providing rigidity while remaining separate Biological Tensegrity suggests that the structure of cell39s cytoskeleton can be changed by altering the balance of physical forces transmitted across the cell s surfaces and this might result in changes in shape and form I For example cultured cells on glass at vs a exible surface round Since many enzymes and other substances that control protein synthesis energy conversion amp growth in the cell may be physically immobilized upon the cytoskeleton changing the cytoskeletal geometry amp mechanics may affect biochemical reactions amp even alter the genes which may be activated amp thus proteins may be made Fully triangulated tensegrity structures once selfassembled may have been selected for through evolution because of their structural efficiency high mechanical strength amp minimal use of materials I em rm 39 i B i cl l 39 D 39 39 Gil 20 nm 50 i 1U ILiil n 15 mm 20 mm Welldefined ornate amp beautiful spatial patterns are found at every levei of organization in iiving organisms in order of increasing size A protein molecules in the coat of a virus a parasite that although not technically alive contains the same types of molecules as those found in living cells B the regular array of microtubules seen in a cross section of a sperm tail 0 surface contours of a polllen grain a singlle celi D cross section of a fern stem showing the patterned arrangement of cells and El flower with a spiral array of petals each made of millions of cells Figure 33 Bsential Gail Bioiogy with ed l Garland Science 1014 0 Summary of shape of molecules amp biological activity 1 2 9 Small molecules are the building blocks of larger molecules a Monomers make polymers make supramolecular complexes and make organelles Covalent and noncovalent electrostatic forces control molecular form and shape a Forces of configuration amp conformation result in biologically active molecules Chemical reactions are reversible depending on rate constants amp the P amp R The source of cellular chemical energy is the hydrolysis of ATP as high energy phosphoanhydride bonds are broken by addition of water hydrolysis
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