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