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Pharmacy Stage 2 > Chemistry of Fe > Flashcards

Chemistry of Fe Flashcards

1
Q

what is the ground state electron configuration of Fe?

A

1s2 2s2 2p6 3s2 3p6 3d6 4s2

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2
Q

what is the electron configuration of Fe2+?

A

1s2 2s2 2p6 3s2 3p6 3d6 (the 4s2 electrons are knocked off instead of the 3d electrons)

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3
Q

what is the electron configuration of Fe3+?

A

1s2 2s2 2p6 3s2 3p6 3d5 (knocks off 2 from 4s2 and 1 from 3d6)

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4
Q

what are the three common structural complex ions formations?

A
  1. octahedral
  2. tetrahedral
  3. square planar
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5
Q

which are more stable, higher or lower oxidation states?

A

lower oxidation states

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6
Q

what are the two categories which ingested iron can be classified into?

A
  1. Iron-bearing haem moiety (contains porphyrin ligand system)
  2. Non-haem containing (no porphyrin ligands)
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7
Q

how is iron used by the body?

A
  1. in bone barrow to create reticulo-endothelial macrophages which store the iron
  2. in muscles (in their myoglobin)
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8
Q

Where is iron mainly stored in the body?

A

liver parenchyma and reticulo-endothelial macrophages

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9
Q

what 4 main body homeostasis are controlled by Fe?

A
  1. metabolism
  2. oxygen transport
  3. energy generation
  4. oxygen transfer
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10
Q

what is the structure of a metallo-protein?

A
  • metal complex in crevice of the protein

- some ligands attached to metal are from the protein (if not all the ligands)

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11
Q

what decides the geometry of the metal bond angles and distances?

A

the protein unit it attaches to

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12
Q

what is a co-factor?

A

A non-protein chemical compound bound to a protein and is required for the protein’s biological activity

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13
Q

what are the 4 categories for cofactors?

A
  • organic
  • inorganic
  • coenzymes
  • prosthetic groups
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14
Q

what is the difference between coenzymes and prosthetic groups?

A
  • coenzymes are loosely bound to an enzyme,

- whilst prosthetic groups are tightly bound.

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15
Q

what are protoporphyrin IX?

A

organic compounds not soluble in basic water. only exists with its iron complex in nature, can’t be found on it’s own.

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16
Q

What are haem’s?

A

prosthetic groups in haemoglobin, myoglobin and cytochrome C

17
Q

what is haemogobin?

A
  • red tetrameric protein (red blood cells) comprising of 2 alpha and 2 beta subunits each containing an iron atom bound to a haem group
  • promotes the diffusion of oxygen throughout the body
18
Q

what is myoglobin?

A
  • red protein containing haem

- binds to iron to carry (facilitate O2 diffusion) and store oxygen in muscle cells.

19
Q

what is myoglobin made up of?

A
  • a single polypeptide chain of 153 amino acids

- and a single prosthetic group

20
Q

What is the charge of the iron that binds to the haem group on haemoglobin?

A

Fe2+ (iron in its ferrous state)

21
Q

How many coordination positions does Fe2+ have, and what do they bind to?

A
  • 6 coordination positions
  • 4 in plane on protoporphyrin and bound to it
  • 2 perpendicular to this ring with 1 bound to a N atom of a His residue in polypeptide chain and the other free to bind to oxygen.
22
Q

Why must the Myoglobin haem group be kept away from solvents?

A

Because Fe2+ can easily oxidise to Fe3+ and this doesn’t bind to oxygen

23
Q

During oxygenation of myoglobin, what role does distal Histidine have?

A

Makes oxygen bind to iron in a bent manner and prevent CO binding in a linear manner

24
Q

what is the amount of oxygen bound a hyperbolic function of?

A

the amount of oxygen present and the affinity of myoglobin for oxygen

25
Q

Haemoglobin transitions between 2 conformational states depending on whether O2 is present or not. What are these states?

A

R state (relaxed) and T state (tensed)

26
Q

What state is favoured by O2 binding?

A

the R state. T state is more stable in the absence of oxygen

27
Q

what happens when O2 binds to Hb in the T state?

A

triggers a change in the conformation to the R state

28
Q

When going from T to R state, bonds are broken and new ones are formed. Which bond is one of the most important ones broken during this transition?

A

the His C3 and Lys C5 bonds

29
Q

what is the effect of oxygen on the porphyrin ring and the haemoglobin helix?

A

promotes flattening of the porphyrin ring

and causes a shift in the helix

30
Q

why is it that once one oxygen molecule binds to one haem group, the other haem groups can bind to oxygen easier?

A

because that polypeptide changes from T to R state therefore pockets of haem are easier to access due to weak interactions being broken

31
Q

why can’t myoglobin be used as an oxygen transporter round the body?

A

because it has a high affinity for oxygen, so will bind to it at the lungs but at the respiring tissues it won’t dissociate. Therefore no more oxygen can bind

32
Q

what is cooperative binding?

A

the binding of one ligand to a protein altering it’s affinity for subsequent ligands

33
Q

why can haemoglobin be used to transport oxygen?

A

because it undergoes structural transition from T to R (low-affinity to high-affinity) therefore would be able to bind and dissociate with oxygen

34
Q

what happens during phase 1 oxidation of drug metabolism?

A
  • oxygen atom is added using cytochrome p450 enzyme.

- NADH, NADPH and O2 required as cofactors

35
Q

how does cytochrome p450 enzyme bind to oxygen?

A

contains a haem group so binds using that

36
Q

what is an iron containing porphyrin?

A

-4 pyrrole rings joined by one carbon bridge, containing Fe2+ at its active site.

37
Q

explain how cytochrome p450 works in drug metabolism?

A
  1. CYP450 bound to Fe3+
  2. drug binds to CYP450Fe3+ complex
  3. NADPH and a reductase enzyme release electrons to reduce Fe3+ to Fe2+
  4. Oxygen is added and binds to Fe2+ in a linear way and Fe3+ created
  5. Another oxygen added via NADPH or NADH and reductase enzyme
  6. Fe3+ binds to O2 in trigonal planar structure
  7. Proton added and H2O released
  8. Drug also leaves oxidised into an alcohol
  9. cycle repeats.
38
Q

what are the disadvantages of too much iron?

A
  • can cause damage to tissues
  • catalyses conversion of H2O2 to free radical ions which attack cell membranes, DNA and proteins
  • cardiac toxicity
39
Q

what is iron deficiency?

A
  • reduces levels of systemic iron conc.

- isn’t a diagnosis, require a diagnosis on the cause of iron deficiency

Pharmacy Stage 2 (85 decks)

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