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Pharmacy Stage 2 > Intro To Bioinorgic Chemistry 1 & 2 > Flashcards

Intro To Bioinorgic Chemistry 1 & 2 Flashcards

1
Q

Most abundant elements in mammalian biochemistry?

A

C, N, O, H, S, P

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2
Q

What are many metals in the body associated with?

A

Proteins

1/3 of proteins are metalloproteins

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3
Q

What happens to the atomic radii down a group and across the period?

A

It increases down group as new shells added causing electron shielding.
Decreases across period as proton number increases but same number of outer electrons so pulls outer shell closer.

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4
Q

What happens to the 1st ionisation energy going down group 1 and 2?

A

It decreases due to electron shielding. Less pull on electron from nucleus so easier to remove from shell.

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5
Q

What happens to the 1st ionisation energy going across the 1st period?

A

It increases due to the smaller atomic radius.

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6
Q

What is electron affinity?

A

The ability of an element to attract an electron. Elements at the top right of the periodic table have the highest affinity.

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7
Q

What is electronegativity

A

The ability of an atom within a compound to attract electrons towards itself. Atoms at top right of periodic table are most electronegative.

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8
Q

What is polarizability?

A

The ability of an atom/ion to be distorted by an electric field.

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9
Q

What are hard atoms/ions?

A

Those with high ionisation energies (small and near fluorine)

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10
Q

What are soft atoms/ions?

A

Those with low ionisation energies and low electron affinity.

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11
Q

What is the difference between soft and hard acids and bases?

A

Soft are more polarisable and form bonds with covalent character.
Hard are less polarisable and form bonds with ionic character.

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12
Q

4 biological roles performed by metals?

A

1) structural
2) catalyst
3) redox
4) others

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13
Q

Factors affecting the role of metals?

A

1) valency
2) ionic radius
3) polarizability
4) hydration energy
5) radius of hydrated ion

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14
Q

What is hydration energy?

A

The ease with which eater molecules can be removed from the metal ion

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15
Q

What is a Lewis-acid?

A

substance that accepts electron pair

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16
Q

What is a Lewis-base?

A

Substance that donates an electron pai

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17
Q

What does the Lewis Theory state?

A

Hard acids prefer Hard bases and Soft acids prefer Soft bases.

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18
Q

What is the predicted stable geometry of compounds with 2,3,4,5,6 pairs of bonds?

A 
2-linear
3-equilateral triangle
4-tetrahedron
5-trigonal bi-pyramidal or square pyramid (which is less stable
6-octahedron
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19
Q

What are co-ordination numbers? And which ones are the most common in biological systems?

A

The number of ligands that can bind to the metal.

Most common ones: 4 and 6 but some metals aren’t fixed to the only one.

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20
Q

What are monodentate ligands

A

only one point of attachment to metal ion.

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21
Q

What are polydentate ligands?

A

more than one point of attachment to the metal ion.

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22
Q

What are macrocyclic ligands?

A

Cyclic molecules with at least 9 atoms that contain at least 3 donor atoms (typically N,O,S or P).

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23
Q

What are the most thermodynamically and kinetically stable ligands?

A

Macrocyclic ligands

24
Q

Why are macrocyclic ligands the most stable?

A

Due to the chelate effect.

Stability increases with more donor atoms in the ring.

25
Q

There are ions in the body. Drugs can behave like chelating ligands. What is the effect of this?

A

The metal ions and drugs can bind to form a ligand-metal complex. This changes the physical and chemical properties of both the metal and ligand.

26
Q

What are tetracyclines used for?

A

1) Chlamydia
2) Rickettsia
3) Brucella
4) Lyme disease
5) Respiratory and genital mycoplasma infections

27
Q

Why had the value of tetracycline reduced over the years?

A

Because of antibiotic resistance

28
Q

What is tetracyclines mode of action?

A
  • targets the 30S subunit
  • it is a bacteriostatic agent
  • it is selective so doesn’t bind to mammalian ribosome, only bacterial one.
  • blocks the binding of aminoacyl tRNA
  • involves Mg2+ ions
29
Q

Metal ions that form chelates with tetracyclines?

A

Mg2+, Ca2+, Al3+, Fe2+, Zn2+

30
Q

What is the drug-metal ratio between metals of 3+ charge and drug and metals of 2+ charge with drug?

A

Drug and M3+ = 3:1 ratio

Drug and M2+ = 2:1 ratio

31
Q

How do Antacids and Anti-ulcer agents interact with tetracyclines?

A

Their metal ions e.g. aluminium and magnesium form a complex with the tetracycline reducing its absorption.

32
Q

Why are tetracyclines not recommended to children?

A

They discolour the teeth turning it yellow/grey/brown ish). This is due to the calcium in teeth.

33
Q

Why are tetracyclines not recommended to pregnant women?

A

because the tetracycline affects skeletal growth due to forming a complex with the calcium ions in bones.

34
Q

What are the roles of carbonic anhydrase?

A
  • regulation of acid/base balance.
  • production of bicarbonate rich aqueous humour secretion.
  • secretion of electrolytes in tissues
  • production of saliva and bile
35
Q

What is the most important physiological reaction catalysed by carbonic anhydrase?

A

The reaction of water with CO2 to form carbonic acid (H2CO3)

36
Q

What metal ion is found in carbonic anhydrase?

A

Zn2+

37
Q

What is the active form of carbonic anhydrase?

A

The basic form (hydroxide group bound to Zn2+)

38
Q

Role of Zn2+ in carbonic anhydrase activity?

A

Zn2+ sits at the bottom of a cleft with 2 distinct faces: hydrophobic and hydrophilic. The hydrophobic face is important for substrate binding and hydrophilic face is for shutting protons in and out

39
Q

Difference between calcium and magnesium ions?

A 
Magnesium has a smaller radius
Calcium coordination number:7
Magnesium coordination number: 6
Magnesium geometry: octahedral
Calcium geometry: irregular
Magnesium exchanges water slowly and calcium exchanges water quickly
40
Q

Roles of magnesium ions are…?

A

1) in the catalytic sites of DNA polymerases. These enzymes bind to 2 magnesium ions at a time.
2) activate tension fibres in muscles
3) stabilise RNA and DNA structures
4) neutralises anions in the cytoplasm

41
Q

What type of phosphates do magnesium ions attach to?

A

Associates with pyrophosphates and polyphosphates. Doesn’t associate with simple phosphates.

42
Q

Wha des phosphorylation do?

A

Switches proteins on and off

43
Q

What do protein kinases and phosphates do?

A

Protein kinases: add the phosphate group

Phosphates: remove the phosphate group

44
Q

What are the three amino acids that phosphorylation can take place on?

A

Serine, threonine, tyrosine

45
Q

How do kinases work?

A

ATP binds to protein vía adenine
Phosphate chain is exposed or weakly bound
Anion centre on protein helps move the triphosphate into position so it can transfer the terminal phosphate group to the requisite amino acid.

46
Q

What nucleic acid structures does Mg2+ bind to?

A

RNA, DNA, tRNA.

role in ribozymes is also important

47
Q

Why do tRNA molecules require Mg2+ ions?

A

tRNA contains regions known as the half-crucifix. Mg2+ helps maintain this shape

48
Q

Why do ribozymes require Mg2+ ions?

A

to catalyse their splicing reaction.

49
Q

Role of Mg2+ in muscle cells?

A

The Mg2+ is bound to ATP. This complex binds to myosin breaking the actin-myosin bridge. ATP.Mg is hydrolysed into ADP.Pi.Mg by ATPase and the energy released is used to attach the myosin head to the actin for contraction.

50
Q

Biological roles of Ca2+

A

1) metabolism
2) cell division
3) cell death (apoptosis)
4) binding to membranes
5) phosphorylation
6) hormone/transmitter release
7) blood clotting

51
Q

binding properties of calcium ions?

A
  • selective but can interact with neutral oxygen donors (carbonyls and ethers)
  • can bind to a number of centres at once (irregular coordination geometry)
52
Q

Ligand properties of Ca2+?

A
  • readily exchange water with other ligands

- ligands on the ion are fluctional

53
Q

What is calmodulin?

A

A small, acidic protein involved in Ca2+ signal mediation in a large number of pathways.

54
Q

Where can calmodulin be found?

A

as part of enzyme complexes i.e. phosphorylase kinase enzyme

55
Q

How many calcium ions can calmodulin bind to?

A

4

56
Q

What groups on calmodulin bind to the calcium ions?

A

Carbonyl and Carboxylate groups

57
Q

Why are specific sets of Lewis bases needed in calmodulin-calcium ion complex formation?

A

in order to not stabilise the cross-links within the protein.

Pharmacy Stage 2 (85 decks)

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