Bioinorganic Chemistry

Question 1

What are the Acid - Base catalysts, and what are they used for?

Answer 1

Zn - Food Digestion Ni - Urea Hydrolysis Fe + Mn - Phosphate Removal in Acid Media

Question 2

What is the steady state?

Answer 2

The steady state is where a cell has all the essential bulk and trace elements, at the
appropriate concentrations, and in the correct forms and normal functioning is
observed – Homeostasis

Question 3

What is the non-steady state?

Answer 3

An imbalance in
the concentration of an element,
either as an excess or a deficiency,
can cause disease, or be a symptom
of disease.

Question 4

What is the dose response curve?

Answer 4

A lower case n curve with a ‘death zone’ at both ends, deficiency one in from the left, toxic effects on in from the right and state of health in the middle. Physiological response go from negative to positive on the y axis, with dose concentration on the x axis.

Question 5

What is element deficiency and how is it treated?

Answer 5

Element deficiency is where the correct amount of the element is not in the body and deficiency is treated by administering the particular element in an appropriate form – usually a simple salt preparation.

Question 6

What is element overload?

Answer 6

Toxicity occurs when an organism has more of an element than it can use, store or excrete.

Question 7

What is the treatment for non-steady state?

Answer 7

Chelation therapy is used for the treatment of these cases/disorders. In this, chelating agents remove metal ions as soluble complexes.

Question 8

What are exogenous elements?

Answer 8

Exogenous elements are those that are not an integral part of a cell’s composition - these are intended to be outside (exo) the body. Exogenous elements have minimal or zero biological role.

Question 9

What does the exogenous response curve look like?

Answer 9

Y axis physiological response positive going up and negative down. X axis concentration going along in a straight line. As it is exogenous it is never positive and curves down, the more toxic the sharper the curve.

Question 10

What is Iron overload?

Answer 10

Although iron is an essential element in all forms of life, in excess it is highly toxic. This condition, referred to generally as iron-overload, is found in many diseases.

Question 11

In Chelation therapy what binds with the metal iron?

Answer 11

Hydroxamic Group R-N(OH)-C(O)-R. The OH group loses a H and just the two O binds.

Question 12

What is mono, bidentate and bridging bonding?

Answer 12

Bonding of amino acids to a metal from Nitrogen (Histidine), Oxygen (Aspartine and Tyrosine) and Sulfur (Cystidine). Mono - one NOS binds to the one metal. Bidentate - Two NOS binds to one metal. Bridging - Two NOS bind to two metals.

Question 13

What is Ferritin and what happens in the Iron storage mechanism?

Answer 13

Ferritin is the Iron storage in plants and animals.
In the storage first Fe(II) is taken up kinetically liable.
The Oxidation occurs when entering the protein (Fe(II) -> Fe(III)) and binds to carboxylate groups.
Ferritin core then grows through Fe(II) oxidation and hydrolysis and uptake of H2PO4 -.
Forms [Fe(O)(OH)8 (FeH2PO4)x H2PO4]

Question 14

What is a Haem, an iron containing porphyrin?

Answer 14

Central metal ion, bonded by 4 nitrogens, which in turn are in a 5 membered aromatic ring, which are all connected by a bond, which has a single and double bond in it (3 Carbons).

Question 15

What haem substituents are hydrophobic and hydrophilic?

Answer 15

Hydrophobic - R-CH3, R-CH-CH2
Hydrophilic - R-CH2-CH2-COO
Both bonded to N 5 membered ring

Question 16

What happens during Fe-O bonding according to MO theory when its Deoxy-Mb before binding?

Answer 16

Fe-O bond formation induces metal spin state change HS → LS and also in O2 (triplet – singlet)
Diamagnetic = All spins are paired

Question 17

What happens during Fe-O bonding according to MO theory when its Oxy-Mb after binding?

Answer 17

Internal electron transfer (i.e. Fe → O2)
Formal assignment as Low Spin Fe(III) + O2.-
(superoxide) with antiferromagnetic coupling
Spin in anti-bonding

Question 18

Why is hemoglobin an allosteric protein?

Answer 18

1-O2 binding at one site on Hb enhances the binding of additional O2 to the same Hb
molecule so O2 binding is cooperative in Hb.
2-O2 affinity of Hb is pH dependent. Both H+ and CO2 promote the release of bound O2. The reverse is also true.

Question 19

Why does myoglobin have a higher affinity for oxygen than hemoglobin?

Answer 19

1-O2 binding in Mb is not cooperative. So binding at one site doesn’t enhance binding at other Mb sites
2-O2 affinity is not pH dependent for Mb

Question 20

What does the oxygen dissociation curve look like for Mb and Hb?

Answer 20

Y Axis - Saturation
X Axis - O2 Pressure
Mb = lower case r shape
Hb = slight s line mainly 0,0 to 10,10

Question 21

Why is Zn so much more useful than other metals in biology?

Answer 21

Availability of Zn in the environment – more readily-abundant than 1st-row d-block
neighbours Ni, Cu; and Group 12 partner Cd
* No redox chemistry; no electron transfer processes c.f. Cu, Fe, Mn
* Flexible co-ordination geometry/number – due to its spherical d10 config – good for catalysis
* Fast ligand exchange c.f. to other biological non-redox active divalent ions e.g. Mg
* Zn(II) is intermediate (HSAB) - suited to coordination by all amino acid donor sites i.e. N-, O- and S-donors.
* High z/r ratio so it is highly polarizing, and, as a result, Zn(II) frequently acts as a (Lewis) acid readily accepting a lone pair and polarising bonds e.g. carbonyl.
* or as a conjugate acid supplying a hard base, e.g. hydroxide, for catalysis (only Cu(II), and trivalent Fe and Mn are better

Question 22

Carboxypeptidase A (CPA) performs what type of cleavage of what bond in a polypeptide chain and what is left?

Answer 22

Type = hydrolytic cleavage
Bond = C-N bond [R-C(O)N(H)-R]

C-O turns to C(O)-O with minus charge
N-H turns to NH3+

Question 23

What is cis-platins structure?

Answer 23

cis-[Pt(NH3)2 (Cl)2]

Question 24

What are the DNA pairs and where are the binding sites for each?

Answer 24

A-T and G-C
A = N on own in 6 ring & N in 5 ring
G = NH on own in 6 ring & N in 5 ring
C = N on own in 6 ring
T = NH on own in 6 ring

Question 25

How does cis-platin bind to 5’-G-3’ 3’-G=5’?

Answer 25

1) cis-platin loses Cl group for H2O group
2) H2O then lost as cis-platin binds to G
3) Other LG (H2O or Cl) then lost and binds to G