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Chemistry Me > Heme > Flashcards

Heme Flashcards

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1
Q

Myoglobin (4) characteristics

A
  1. A protein that stores and transports oxygen in muscles (i.e heart and skeletal)
  2. Provides oxygen for metabolic processes
  3. Used in conversion of nitric oxide to nitrate to enhance cellular respiration
  4. Intercepts reactive oxygen species
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2
Q

Hemoglobin - what does it do? When is it’s affinity for O2 high? Low?

A
  1. Transports oxygen from the lungs to tissue and CO2 from tissues to lungs
    a. High affinity for oxygen in arterial circulation
    b. Low affinity for CO2, phosphates, hydrogen, and chloride ions
  2. In venous circulation:
    a. low affinity for O2
    b. high affinity for CO2, phosphates, hydrogen, and chloride
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3
Q

Which two forms can iron exist within Hgb? Which one binds oxygen?

A
  1. Fe2+ & Fe3+
  2. Fe2+
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4
Q

What type of bond is a sigma bond? Which orbital makes these bonds?

A
  1. Single bond
  2. S-orbital
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5
Q

Which type of bond is a Pi bond? Which orbitals form these?

A
  1. Multiple bonds
  2. P orbitals
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6
Q

Heterocyclic macrocycles (>10 atoms) composed of four modified pyrrole subunits connected by carbon bridges; highly conjugated aromatic compound

A

Porphyrins

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7
Q

What are electron-rich species (nonmetal or polyatomic ions) that bind to a metal ion (i.e iron) to stabilize the charge and help to solubilize? What shape does iron assume when all six bonds are made?

A
  1. Ligands
  2. Octahedral
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8
Q

An inactive protein that heme binds with to make it more water soluble and activate its functionality

A

Apoprotein

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9
Q

Binds to iron at the bottom (5th) site of the hemoglobin causing the iron to sit slightly below the plane

A

Histadine

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10
Q

Fetal hemoglobin has a higher or lower affinity for O2?

A

Higher

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11
Q

What makes myoglobin a “monomeric” heme protein?

A

It has (1) apoprotein and (1) heme

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12
Q

T/F: hemoglobin is a tetromer, meaning it has (4) apoproteins bound with (4) heme proteins

A

True

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13
Q

What type of structure does myoglobin assume?

A

Tertiary

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14
Q

What type of structure does hemoglobin assume?

A

Quarternary

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15
Q

In terms of the subunits, how is adult hemoglobin different from fetal hemoglobin?

A

Adult has (2) alpha, (2) beta subunits; fetal has to (2) alpha and (2) gamma subunits

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16
Q

T/F: when the 1st oxygen binds Hgb, the other (3) sites change conformation and oxygen affinity increases as more oxygen is bound

A

True

17
Q
A

Oxyhemoglobin. R-State. “Relaxed state”

18
Q
A

Deoxyhemoglobin. T-state - “Tense state”

19
Q

How many coordination sites does hemoglobin have?

A
  1. Six
  2. 4 nitrogen, 1 oxygen, 1 histadine
20
Q

(4) ligands that can bind to the heme proteins

A
  1. Oxygen
  2. Carbon dioxide
  3. Carbon monoxide
  4. Cyanide
21
Q

T/F: myoglobin undergoes cooperative binding

A

False. Myoglobin only has 1 binding site, whereas hemoglobin has 4 binding sites and does undergo cooperative binding

22
Q

T/F: myoglobin has a higher affinity for oxygen than hemoglobin

A

True

23
Q

T/F: myoglobin holds onto oxygen supply until levels in the muscles are very low

A

True

24
Q

T/F: fetal hemoglobin strongly binds 2,3-bisphosphoglycerate

A

False. It only weakly binds fetal hemoglobin. This is why it has a higher affinity for oxygen than adult hgb which does bind BPG

25
Q

What is the purpose of 2,3-biphosphoglycerate (BPG)?

A
  1. Binds only to deoxyhemoglobin (stabilizes hgb)
  2. Lowers oxygen affinity by shifting equilibrium to the left
  3. Facilitates unloading of oxygen
26
Q

What are the (3) different ways carbon dioxide is transported?

A
  1. Dissolved gas
  2. Bicarbonate
  3. Bound to the protein of hemoglobin (carbaminohemoglobin)
27
Q

Oxygen dissociation is affected by what (3) things (Bohr-Haldane effect)

A
  1. Increasing temperature
  2. Lowering blood pH
  3. Inreasing partial pressure of CO2
    **Affects the conformational change ability of the proteins in Hgb
28
Q

T/F: Carbon monoxide binding is irreversible

A

False. It is reversible

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