BIOINORGANIC CHEMISTRY

Question 1

Define metallomics

Answer 1

the study of metal elements in life, cells and tissues

Question 2

ions of low charge…

Answer 2

exchange rapidly

Question 3

ions of high charge…

Answer 3

have a long half life

Question 4

initial earth atmosphere

Answer 4

H and CH4
reducing atm
Fe2+ dominated as Cu2S (Cu+) in its reduced state is insoluble
mostly Fe extracellular

Question 5

later earth atmosphere

Answer 5

O2 started forming
oxidising atm
Cu2+ dominated as Fe2O3 (Fe3+) in its oxidised state is insoluble
mostly Cu extracellular

Question 6

define metalloprotein

Answer 6

metal containing protein. most function as catalytic enzymes.

Question 7

main functions of biological metal ions

Answer 7

e.t
transport of small molecules
activation
catalysis

Question 8

define hard donor

Answer 8

doesn’t like to share electrons so forms ionic bonds

goes for higher oxidation state metals : hard metal

Question 9

define soft donor

Answer 9

more diffused electron cloud so forms covalent bonds

goes for lower oxidation state metals : soft metal

Question 10

describe evolution due to O2

Answer 10

O2 is a powerful oxidant which may have led to higher evolution and the need for specialised O2 transport systems to supply inaccessible tissues with O2.

Question 11

3 types of O2 transporters

Answer 11

biological O2 carriers (general)
Hb and Mb
Hr and Hc

Question 12

different forms of O2

Answer 12

dioxide (0), BO = 2, 2 spins, paramag
super oxide (1-), BO = 1.5, 1 spin, paramag
peroxide (2-), BO = 1, no spin, diamag

Question 13

outline Hemeglobin

Answer 13

in mammals
4 heme units in tetramer globular protein
Fe2+ oxidised to Fe3+
superoxide bound
becomes planar due to smaller Fe3+ than 2+

Question 14

outline Hemocyanin

Answer 14

in arthropods and molluscs
1 active site
both Cu1+ oxidised to Cu2+
peroxide bound

Question 15

outline hemerythrin

Answer 15

in non-mammals
multimer 8 subunits
peroxide bound

Question 16

what is met- form

Answer 16

sometimes O2 does not bind to the metalloprotein. This is called a met form. the oxidation of the metal still occurs.

Question 17

what limited making Hb model complexes

Answer 17

dimerisation would occur where Fe-O-Fe bonding could occur due to excess PFe2+

Question 18

2 methods to stop dimerisation of Hb model complex

Answer 18

using cold non-aqueous solution to slow down reaction

use sterically crowded porphyrin rings with ligands designed to mimic hydrophobic cleft in protein.
Ligand = 1-methyl imidaziole
picket fencing or large straps prevent the dimer forming.

Question 19

Hc model complexes

Answer 19

show stabilisation of the side on mode of O2 coordination at extremely low temperatures

Question 20

Hr model complexes

Answer 20

self-assembly of tridendate ligands but forms without a vacant coordination site for O2

Question 21

Having a low redox potential means…

Answer 21

a substance wants to be oxidised

Question 22

If Eº>0

Answer 22

G<0
reaction will happen spontaneously

as G=-nFEº

Question 23

transition metals offer…

Answer 23

1 e.t

Question 24

3 main types of metalloproteins for et

Answer 24

cytochromes
FeS clusters
Blue Cu proteins

Question 25

define outer sphere metalloprotein

Answer 25

means there is no bridging ligand that carries the electrons. electron just goes straight to next transfer molecule

Question 26

outline cytochromes

Answer 26

have Fe-porphyrin haem group that has 2 axial ligands 6 coordinate, low spin, reduced state d orbitals do not point towards ligands minimal structural change during et

Question 27

outline ferrodoxins

Answer 27

centres made of Fe-S arrangements high spin d orbitals to not point towards lignands minimal structural change during et

Question 28

outline Blue Cu proteins

Answer 28

ligand donor set that is held firmly by protein polypeptide distorted geometry between Cu1+ and Cu2+ 4 coordinate is preferred by Cu1+ but ligands support both states

Question 29

what is the enteric state

Answer 29

shape of an et protein similar to the transition state of the complex. allows et to occur rapidly. weird geometry, distorted active site

Question 30

coupling of e- and proton

Answer 30

allows for subsequent oxidation steps to occur at the metal centre without extending redox range. binding a proton to a reducing substrate also minimises charge repulsion.

Question 31

hierarchy of et proteins

Answer 31

Cu oxidising centres heme FeS flavin reducing centres

Question 32

outline superoxide dismutase

Answer 32

takes superoxide and turns it into a less reactive molecule catalyses detoxification 2 superoxide = 1 oxygen, 1 hydrogen peroxide called a ping pong reaction

Question 33

Cu|Zn superoxide dismutase (SOD)

Answer 33

Zn2+ ensures structural integrity of the protein but has no redox/et ability as it is 3d10. Cu2+ does the catalysing

Question 34

outline oxidases

Answer 34

reduce oxygen as well as oxidative dehydrogenation oxygen can be inserted into substrate by monooxygenases (1 atom of O2) or by dioxygenases (2 atoms of O2)

Question 35

galactose oxidase oxidises...

Answer 35

1º alcohols to aldehydes

Question 36

what are Zn enzymes used for

Answer 36

For acid base catalysis as biology cannot accomodate the extreme pH for H+ ND OH- to perform hydrolysis.

Question 37

Zn2+...

Answer 37

good lewis acid forms labile bonds with O donors forms inert bonds with N donors 3d10 no CFSE = many geometries

Question 38

2 types of Zn enzyme mechanisms

Answer 38

Zn-hydroxide : where Zn2+ generates a HO- nucleophile Zn-carbonyl : where Zn2+ accepts a lone pair from C=O taking e.d from O, weakening C=O bond and making C electrophilic

Question 39

outline carboxypeptidase (CPD)

Answer 39

catalyse cleavage of peptides as COO terminal | CPD A = aromatics, CPD B = basic aa residues

Question 40

2 requirements for CPD

Answer 40

facilitating nucleophilic attack on C=O using a reactive nucleophile/activating CO group stabilise carbon tetrahedral intermediate activate the amide N to form a suitable leaving group

Question 41

outline carbonic anhydrase

Answer 41

catalyses reaction of dissolving CO2 into water. H2O + CO2 = HCO3- + H+ = H2CO3

Question 42

outline alcohol dehydrogenase

Answer 42

catalyses the oxidation of 1º alcohols to aldehydes and reverse reaction uses NAD+ for a 2 e.t using H- 2 active sites = 1 catalytic and 1 structural

Question 43

higher alcohols are...

Answer 43

oxidised more rapidly

Question 44

cobalt can be substituted for Zn too...

Answer 44

analyse it. It has a similar radius and does not disrupt protein conformation must be used because Zn 3d10 cannot be analysed.