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22 Cards in this Set

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Main category of globular proteins, what makes them unique:
Heme proteins - have a tightly bound HEME prosthetic group.
4 important globular hemeproteins:
-Hemoglobin
-Myoglobin
-Cytochrome
-Catalase
How the heme group functions in Cytochrome:
As an electron carrier
How the heme group functions in Catalase:
In the active site where H2O2 is broken down.
How the heme group functions in Hemoglobin and myoglobin:
Reversibly binds oxygen
2 primary components of the heme group:
-Protoporphyrin IX
-Ferrous iron (Fe2+)
How many bonds can Fe make?
6
(4 to Nitrogens in porphyrin ring)
(2 to other things)
What are the 2 'other things' to which Fe binds in myoglobin and hemoglobin?
-One is to a histidine
-One is to oxygen
2 types of tissue that contain myoglobin:
-Heart
-Muscle
What is the structure of myoglobin like?
80% alpha helix
Where is the heme group in myoglobin situated?
In a crevice lined with nonpolar amino acids
What holds the porphyrin ring in place in myoglobin?
A proximal Histidine residue
What is the function of the distal histidine in myoglobin's heme binding crevice?
To create a special microenvironment that helps oxygen bind iron reversibly.
What type of tissue contains hemoglobin?
Red blood cells only
Major hemoglobin in adults:
Hemoglobin A
What is HbA made up of?
-2 alpha chains
-2 beta chains
Noncovalently the 2 aB dimers are held together
2 forms in which hemoglobin can be found:
-T
-R
When is hemoglobin in the T state?
When it's TAUT and nonoxygenated (deoxyhemoglobin); it allows for more ionic and H-bonds to be present between the 2 aB dimers.
When is hemoglobin in the R state?
When it's RELAXED and oxygenated - the O2 binding breaks some of the ionic and H-bonds between the 2 aB dimers.
Which form of hemoglobin is low O2-affinity, and which is high O2-affinity?
T = low affinity for oxygen

R = high affinity for oxygen
Why is relaxed hemoglobin higher in terms of oxygen affinity?
Because of cooperative binding - as it relaxes, it becomes easier for oxygen to bind.
Which has higher oxygen affinity, hemoglobin or myoglobin?
Myoglobin