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23 Cards in this Set
- Front
- Back
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typical characteristics of a metabolic pathway
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• first catalyzed reaction
• rate limiting • highly regulated • largest negative delta G =not reversible • feedback regulation • end product inhibits first enzyme by allosteric binding |
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Allosteric regulation
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• binding of enzyme to site different from site where substrate binds
• can be positive (activating) or negative (inhibitory) • can show positive cooperativity or negative cooperativity--alters affinity of binding at site other than allosteric site (substrate binding site) |
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homotropic modulator
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allosteric regulatory that is a substrate of the target enzyme
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heterotropic modulator
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allosteric regulator that is NOT a substrate for the target enzyme
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homotropic modulator kinetics
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classic sigmoidal curve
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heterotropic modulator kinetics
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• two possibilities
• Vmax stays same and K0.5 increases or decreases (similar to competitive inhibition) • Vmax increases or decreases and K0.5 stays same (similar to non-competitive inhibition) |
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role of hemoglobin
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deliver O2 to tissues deep within organisms
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structure of hemoglobin
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• globin fold with heme group (binds O2)
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heme group structure
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• porphyrin ring
• Fe in plane with 4 Nitrogen • 2 binding planes for Fe • binds His on globin protein • binds (covalently) O2 |
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location of alpha globin genes and number
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2 on each chromosome 16--individual has 4 total alpha globin genes
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location of beta globin gene and number
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1 per chromosome 11
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5 types of globin genes and when expressed
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• epsilon=early embryonic
• gamma=embryonic until birth • sigma=low starting just before birth and in adult • beta=after birth • alpha=always |
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3 important hemoglobins
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• HbA (α2β2)=major in adult
• HbA2 (α2 δ 2) = 2% of adult Hb • HbF (α2 γ2)=fetal |
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myoglobin
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• muscle cells
• monomer • same secondary structure as hemoglobin • higher affinity for O2 than Hb=aids in unloading O2 from Hb to myoglobin in peripheral tissue (muscles) • has low P50=1 torr (bind O2 at lower pO2 than hemoglobin) (p50 of Hb=26 torr) |
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3 allosteric regulators of hemoglobin
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• oxygen
• 2,3-BPG • H+ • CO2 (indirectly thur H+) |
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oxygen as allosteric regulator of hemoglobin
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• homotropic, alloteric activatory, positive cooperativity
• each O2 that binds makes it easier and easier for next one to bind--produces sigmoidal binding curve |
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2 states of Hb
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• tense (T) state=harder for O2 to bind (lots H bonds to break)=difficult for O2 to bind, but still does in lungs because pO2 so high
• relaxed (R) state=facilitates O2 binding=easy for O2 to bind |
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2, 3-BPG as a allosertic regulatory of Hb
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• heterotropic, negative allosteric regulator
• made in RBCs • only binds T state and binds beta subunit only • stabilizes T state • decreases O2 binding affinity • helps unload O2 at peripheral tissues (low pO2 location) • is present in lungs, but pO2 so great O2 will bind anyways • increased level at higher altitudes • aids in transfer O2 between mom and fetus |
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how does 2, 3-BPG aid in transfer of O2 from maternal to fetal blood?
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• HbF does not have beta subunit, only gamma, which 2,3-BPG does NOT bind
• HbF has greater affinity for O2 than maternal H2A |
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H+ as an allosteric regulatory of Hb
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• Bohr Effect
• as pH decreases ([H+] increases), Hb affinity for O2 decreases • slightly lowering pH had large effect on O2 affinity at lower pO2 (peripheral tissue)=aids unloading of O2 in peripheral tissues • changes in pH have little effect on O2 affinty at high pO2 (lungs) |
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Bohr effect at peripheral tissues
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• high CO2
• CO2 imported to RBC, converted to H2CO3 (carbonic acid) by carbonic anhydrase • carbonic acid dissociates to bicarbonate and H+ (b/c weak acid) • H+ displaces O2 from hemoglobinO2 released to tissue • bicarbonate exchanged for Cl- as transported out of cell • bicarbonate travels to lungs |
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Bohr effect at lungs
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• high pO2 causes O2 to kick H+ off hemoglobin
• H+ released from hemoglobin to bind to bicarbonate (which enters cell/ exchanged with Cl-) to form carbonic acid • carbonic acid converted to Co2 and H2O by carbonic anhydrase • CO2 diffuses across membrane, exhaled |
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CO2 as an allosteric regulatory of Hb
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• indirectly (thru Bohr effect)
• heterotrophic regulatory, negative --inhibits O2 binding Hb |
