BCH 361 Lecture Notes - Lecture 13: Cytochrome, Heme, Pyrrole
5 Feb 2017
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Document Summary
Heme is a protoporphyrin - porphyrins have four pyrrole rings (circled) Fe+2 has six coordination bonds, four are coordinated with four n, and two are perpendicular to the ring"s plane. Heme secured by a hydrophobic pocket that prevents heme from leaving. Carbon monoxide kills because it binds heme better than o2. Co is highly toxic as it competes with oxygen. It blocks the function of myoglobin, hemoglobin, and mitochondrial cytochromes. Co binds to free heme > 20,000 times better than o2. Is a tetramer (complex of 4 proteins, each with a heme group) Binds o2 in lungs and delivers to muscle and other cells. Has to bind o2 when [o2] is high (lungs) (13 kpa) Has to release o2 when [o2] is low (muscle) (4 kpa) Has to bind to o2 very strongly (even at low) [o2] Oxygen has a higher affinity for hemoglobin in the r state (tense)
