BMB 401 MSU (FOLEY) Exam 1 with
Complete Solutions
Heme Correct Ans-Iron containing prosthetic group ( planar) located in hydrophobic pockets
Globin Correct Ans-protein component made up of alpha and beta chains. (Polypeptides
chain that had globin fold)
What type of porphyrin is heme Correct Ans-iron containing
organic component of heme Correct Ans-protoporphyrin IX
inorganinc component of heme Correct Ans-Ferric Fe3+
Ferrous Fe2+
(central iron ions)
What type of ring is Protorphyrin? Correct Ans-Tetrapyrrole
Tetrapyrrole Correct Ans-made up of four pyrrole rings linked by methine bridge
Tetrypyrrole attachements Correct Ans-Four methyl groups, two vinyl groups, and two
propionate side chains are attached to the central tetrapyrrole.
distal histidine Correct Ans-acts as a gatekeeper allowing for the proper entry and exit of
oxygen
,proximal histidine Correct Ans-The residue occupying the fifth coordination site to which iron
can bind in hemoglobin and myoglobin
Shape of heme Correct Ans-non planar
Fe 2+ to Fe3+ Correct Ans-When oxygen binds to Fe2+, and an electron is partially transferred
from ferrous iron to oxygen, this results in Fe3+ and . O2- (superoxide). This changes the
organization of electrons in iron, causing the iron atom to become smaller
Difference in Fe 3+ from Fe 2+ Correct Ans-Fe 3+ is smaller and can enter the center of the
porphyrin ring, it also makes the heme group planar
Methemoglobin Correct Ans-Cannot bind oxygen because it has Fe 3+
Oxyhemoglobin Correct Ans-Hemoglobin combined with oxygen (Fe 3+)
De-oxyhemoglobin Correct Ans--Hemoglobin with no bond oxygen (Fe 2+)
-Salt bridges intact
-Molecules is in a tense state
Iron state needed to bind Oxygen Correct Ans-Ferrous Iron ( Fe 2+)
How is methemoglobin formed? Correct Ans-when the oxidation state is deranged by genetic
mutations or environmental stressors (nitrates, some antibiotics and local anesthetics).
Myoglobin saturation curve Correct Ans-
P50 Correct Ans-the partial pressure of oxygen when hemoglobin is 50% saturated
,Y ( saturation curve) Correct Ans-the fraction of possible oxygen binding sites filled,
Hemoglobin Saturation Curve Correct Ans-right shifted from Myoglobin
How does hemoglobin function Correct Ans-dimer of dimers
Reaction of Dimers to Oxygen dimer Correct Ans--One dimer rotates with respect to the
other
-Salt bridges between dimers break
-Once Salt bridges break, Oxygen cam bind more easily
(Cooperativity)
The types of Dimers in hemoglobin Correct Ans-alpha1 beta1 dimer
alpha2 beta-2 dimer.
Cooperativity Correct Ans-activity at one functional site affects the activity at others.
Tense State Correct Ans-The quaternary structure observed in the deoxy form of hemoglobin,
deoxyhemoglobin
Effects of the tense state Correct Ans--Molecules is constrained by subunit-subunit
interactions
-Oxygen has less affinity for heme groups is lower
Relaxed State Correct Ans-the oxygen-binding sites are free of strain and are capable of
binding oxygen with higher affinity
, Effects of the relaxed state Correct Ans--a 15° rotation that occurs between the alpha-1 beta-
1 dimer and the alpha-2 beta-2 dimers( when oxygen binds)
-Oxygen is easier to bind; Oxygen Affinity for heme increases
R-state vs T- State binding curve Correct Ans-
2,3-Bisphosphoglycerate Correct Ans-Helps improve oxygen delivery in tissue by decreasing
affinity for hemoglobin
Hemoglobin without 2,3-Bisphosphoglycerate Correct Ans-reluctant to release oxygen
How does 2,3-bisphosphoglycerate regulate hemoglobin? Correct Ans-sits in the central
channel between the four subunits of the tetramer and stabilizes interactions between the four
subunits,
Why does fetal blood have higher affinity Correct Ans-fetal hemoglobin, HbF, has a gamma-
globin peptide instead of a beta-globin peptide. Gamma-globin has a serine in place of histidine
143.
What state does histidne protonation favor Correct Ans-the tense state (O2 release)
When does protonation of histidine occur? Correct Ans-during decreased blood pH
(seen during high metabolic conditions.)
The Bohr effect Correct Ans-The regulation of oxygen binding by hydrogen ions and carbon
dioxide
The process of the Bohr effect Correct Ans--While being produced, CO2 is released into the
blood from tissues where it holds a high partial pressure
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