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eCHM2942 > BIOINORGANIC CHEMISTRY > Flashcards

BIOINORGANIC CHEMISTRY Flashcards

1
Q

Define metallomics

A

the study of metal elements in life, cells and tissues

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2
Q

ions of low charge…

A

exchange rapidly

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3
Q

ions of high charge…

A

have a long half life

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4
Q

initial earth atmosphere

A

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

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5
Q

later earth atmosphere

A

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

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6
Q

define metalloprotein

A

metal containing protein. most function as catalytic enzymes.

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7
Q

main functions of biological metal ions

A

e.t
transport of small molecules
activation
catalysis

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8
Q

define hard donor

A

doesn’t like to share electrons so forms ionic bonds

goes for higher oxidation state metals : hard metal

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9
Q

define soft donor

A

more diffused electron cloud so forms covalent bonds

goes for lower oxidation state metals : soft metal

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10
Q

describe evolution due to O2

A

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.

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11
Q

3 types of O2 transporters

A

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

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12
Q

different forms of O2

A 
dioxide (0), BO = 2, 2 spins, paramag
super oxide (1-), BO = 1.5, 1 spin, paramag
peroxide (2-), BO = 1, no spin, diamag
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13
Q

outline Hemeglobin

A

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

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14
Q

outline Hemocyanin

A

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

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15
Q

outline hemerythrin

A

in non-mammals
multimer 8 subunits
peroxide bound

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16
Q

what is met- form

A

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

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17
Q

what limited making Hb model complexes

A

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

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18
Q

2 methods to stop dimerisation of Hb model complex

A

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.

19
Q

Hc model complexes

A

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

20
Q

Hr model complexes

A

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

21
Q

Having a low redox potential means…

A

a substance wants to be oxidised

22
Q

If Eº>0

A

G<0
reaction will happen spontaneously

as G=-nFEº

23
Q

transition metals offer…

A

1 e.t

24
Q

3 main types of metalloproteins for et

A

cytochromes
FeS clusters
Blue Cu proteins

25
Q

define outer sphere metalloprotein

A

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

26
Q

outline cytochromes

A

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

27
Q

outline ferrodoxins

A

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

28
Q

outline Blue Cu proteins

A

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

29
Q

what is the enteric state

A

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

30
Q

coupling of e- and proton

A

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.

31
Q

hierarchy of et proteins

A

Cu oxidising centres
heme
FeS
flavin reducing centres

32
Q

outline superoxide dismutase

A

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

33
Q

Cu|Zn superoxide dismutase (SOD)

A

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

34
Q

outline oxidases

A

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)

35
Q

galactose oxidase oxidises…

A

1º alcohols to aldehydes

36
Q

what are Zn enzymes used for

A

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

37
Q

Zn2+…

A

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

38
Q

2 types of Zn enzyme mechanisms

A

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

39
Q

outline carboxypeptidase (CPD)

A

catalyse cleavage of peptides as COO terminal

CPD A = aromatics, CPD B = basic aa residues

40
Q

2 requirements for CPD

A

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

41
Q

outline carbonic anhydrase

A

catalyses reaction of dissolving CO2 into water.

H2O + CO2 = HCO3- + H+ = H2CO3

42
Q

outline alcohol dehydrogenase

A

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

43
Q

higher alcohols are…

A

oxidised more rapidly

44
Q

cobalt can be substituted for Zn too…

A

analyse it. It has a similar radius and does not disrupt protein conformation

must be used because Zn 3d10 cannot be analysed.

eCHM2942 (4 decks)

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