CHEM 191 Lecture 18 Flashcards
biological oxidants must themselves be able to…
be reduced and then re-oxidised when they pass on electrons
what is a catalyst
a substance the increases the rate of a chemical reaction by providing an alternative mechanism for the reaction - a catalyst isn’t used up in the reaction
transition metals are found in many ____
enzymes
what are transition metal complexes
compounds in which a transition metal cation has bonded to it a number of ligands
what is a ligand
a molecule or ion in which one or more donor atoms have a lone pair of electrons
what is a coordinate bond
a covalent bond in which a metal doesn’t have electrons it has a positive charge and a donor that has a lone pair of electrons - so both electrons come from the non-metal - the charge of the metal in these bonds isn’t changed because it hasn’t gained any electrons
are ligands lewis acids or bases
lewis bases as they donate a pair of electrons to the transition metal ion
what charge do ligands have
negative or neutral
in metalloprotiens, the donor atom bonds to the transition metal are found in the ______________
side chains (R groups) of amino acids
protein chemistry is all about ____
side chains
what are heme-based ligands
ligands in which 4 nitrogen donor atoms are arranged in a cyclic ligand, called a heme - these ligands are important for transport
in most cases heme based ligands form complexes with _____
Fe2+ and Fe3+
when ligands bond to a transition metal ion does the reduction potential change
yes
what is tuning
small changes to the structure of the ligands that change the reduction potential of the metal ion
what is the E0 for a concentration cell
zero because standard conditions means 1 mol per litre concentrations and if both of the half equations are the same then there is no electron flow and therefore no reduction potential
