DNA, RNA and proteins Flashcards
properties of water
hydrogen have a partial positive charge and oxygen as a partial negative charge
oxygen has 6 valence electrons, needs two to fill octet
oxygen is sp3 hybridised, tetrahedral arrangement
difference in electronegativity between hydrogen and oxygen
examples of non-covalent interactions
ionic (coulombic)
dipole
van der Waals (London)
hydrophobic effect
ionic (coulombic)
electrostatic interactions between permanently charged species
or between ion and a permanent dipole
dipole interactions
electrostatic interactions between uncharged but polar molecules
London forces
weak interactions between all atoms
regardless of polarity
attractive (dispersion) and repulsive (steric) component
hydrophobic effect
common phenomenon associated with the ordering of water molecules around non polar substances
hydrogen bonds
strong dipole-dipole that arise between covalently bound hydrogen and lone pair of electrons
normally involve two electronegative atoms
strongest when bonded molecules allow for linear bonding patterns
three atoms in a line
hydrogen bonding in water
water can be a hydrogen donator and acceptor
up to 4 hydrogen per water gives it its high boiling and melting point and large surface tension
in water it is cooperative
hydrogen bonds between neighbouring molecules are longer and weaker compared to the one between HO in water
proton acceptor
electronegative atom not covalently attached to the hydrogen
proton donor
atom covalently bound to the hydrogen
hydrogen bonding importance
unique water properties
structure and function of proteins
structure and function of DNA
structure and function of polysaccharides
binding of substrates to enzymes binding of hormones to receptors
matching of mRNA and tRNA
hydrogen bonding in drug design
25% of drugs contain fluorine because it takes place of the H in a chemical structure
very electronegative therefore electron withdrawing
CF3 is withdrawing and can decrease basicity of amino groups, fewer positive charges so can penetrate cells more effectively
when is water a good solvent
amino acids and peptides
small alcohols
carbohydrates
when is water a poor solvent
non polar gases
aromatic moieties
aliphatic chains
the association or interaction of non polar molecules or components of molecules in the aqueous solution is one of the main factors behind
protein folding
protein-protein association
formation of lipid micelles
binding of steroid hormones to their receptors
do not arise because of some attractive direct force between two non polar molecules
