Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

27 Cards in this Set

  • Front
  • Back
Where does myoglobin transport 02? Hemoglobin?
Through cytosol to mitochondria; (Hb) from lungs to peripheral tissues, and C02 and H+ from periph to lungs
simple protein
polypeptide only
conjugated protein
polypeptide and cofactor
cofactor (prosthetic group)
nonpeptide group essential for protein's function
Mb & Hb are __________ proteins
What prosthetic group does Mb contain? Hb?
Both contain heme
Structure of Hb
4 subunits, each with 1 polypeptide chain (alpha or beta) and 1 heme. Subunits are similar to Mb
Ionic metal bonding
-electrons not shared
-transient complexes
-ex. Na+, K+, Mg2+. Ca2+ (alkali and alkaline earth metals)
Covalent metal bonding
-electrons shared
-both elec. from ther nonmetal atom (coordinate covalent)
-ex. iron, zinc, copper (transitional metals)
Ferrous Iron
Ferric Iron
Fe3+ (hemin)
Heme structure (6)
1) Protoporphyrin IX (organic part) + heme
2) Large (>70 atoms)
3) Planar
4) aromatic
5) Nonpolar except for 2 COO-
6) Unshared e- pairs of N bonded to Fe/delocalized into ring system
Iron in heme (3)
1) Tightly bound to 4 N (coordinate covalent bond)
2) Can bind 2 more atoms
3) ferrous (Fe2+)
Heme-polypeptide interactions (3)
1)Nonpolar. Pep has pocket for heme
2) coordinate covalent bond (btw hist and iron
3) Ion pairing (heme COO- groups with 2 cationic side chains - arg45 and his97)
Coordinate covalent bond of heme-polypeptide
1)btw his side chain and iron
2) 5th coordination position of iron (?)
3) Proximal his: 93, or F8 in Mb helix (?)
O2 binding site (4)
1)Fe2+ (e-'s come from O)
2)6th coordination position
3)opposite of proximal his binding
4)near to a distal his chain, which stablizes
Oxygenation vs Oxidation of Heme
Oxygenation: heme+O2 <==> heme-O2
-fast, reversible.
-e- pair shared
Oxidation: heme-O2 --> hemin +O2- (superoxide)
-e- transferred
-hemin cannot bind O2
1) metHb or metMb. Hb/Mb with hemin instead of heme
2) result of oxidation
3) reversed in vivo by enzymes and reductants
4) can result in cyanosis
5) possible causes: food additives, drugs, enzyme deficiency
6) treated with reducing agents (eg - vita C)
What is the result of methemoglobinemia
Cyanosis (>10% Hb is met Hb)
Main chain structure of Mb
75% alpha helixes
8 helixes in 2 layers linked by loops
common structure - "globin fold"
Mb structure: Side chains
1) Polar on surface/Nonpolar in interior
2) Folded has heme site
3) Bound heme is less oxidizable
O2 disassociation equation
Y = pO2/(pO2+P50)

Y = fractional saturation
p50 = pO2 required for 50% saturation
p50 for Mb
1 torr
O2 binding curve of Mb (3)
-as the pressure of O2 increases, the amount of O2 needed for half saturation (p50) of Mb increases.
-i.e. as the amount of O2 increases, the affinity for O2 decreases
p50 (3)
-O2 level needed for half saturation
-pO2 where [Mb=MbO2]
-p50 INCREASE means O2 affinity DECREASE
p50 of Hb
26 torrs
Diff btw Mb & Hb binding curves
- Hb more to right :. Hb is ALWAYS less saturated than Mb
- Hb curve sigmoidal (Mb is hyperbolic)
- Hb curve is steeper in middle :. Hb is more sensitive to pO2 changes in middle