BIO 311D 2nd Edition Lecture 27 Outline of Last Lecture I. Hormones influence excretory tubules II. Where is the respiratory epithelium?III. Principles of DiffusionIV. Counter Current Exchange Outline of Current Lecture I. Counter- Current ExchangeII. Partial Pressure Differences Affect DiffusionIII. Hemoglobin in red blood cells binds O2IV. Clicker quiz questions about hemoglobinV. Circulatory system Current LectureI. Counter- Current ExchangeA. Birds1. First inhalation posterior air sacs First exhalation push through lungsin one direction second inhalation anterior air sacs second exhalation 2. Helps them fly (stay in the air) II. Partial Pressure Differences Affect DiffusionA. The mount of O2, is measured as a partial pressure, which includes both the total atmospheric pressure (760 mm Hg at sea level) and the % of total air each individual gas comprises (O2 is about 21%)a. Amount of oxygen available affected by the amount available in the air (roomfilled with people working out) B. Gases diffuse across membranes from regions of higher partial pressure to lower partial pressure (gradient P1- P2) C. Oxygen diffuses to equilibrium in the lung alveoli III. Hemoglobin in red blood cells binds O2A. An example of a “respiratory pigment” Respiratory proteins bind O2 molecule reversiblyB. There’s a net transfer of O2a. Into blood near the lungs (where inhaled)b. Out of blood at metabolizing cells (where oxygen is being used up)c. O2 loads in the lungs, unloads in the tissues C. Hemoglobin exhibits cooperativity- i.e. if O2 binds to one subunit; this increases the affinity of the other subunits for O2. The S-shaped curve reflects this acceleration. a. Myoglobin has only one globin unit, so has no cooperativity, no S-shaped curveb. The oxygen binding curve of hemoglobin1. Blood near respiring cells, P-O2 about 402. Oxygenated blood in lungs P-O2 about 100VI. Clicker quiz questions about hemoglobinA. When hemoglobin in red bloodcells is in an area where the P-O2 is 40 mm Hg, about whatpercent of that hemoglobin isbound with O2? – 75% B. In lung alveoli, hemoglobin willload up on O2 until it’s aboutwhat % saturated? - 100%C. Blood hemoglobin that has justbeen in lung capillaries (P-O2=100) is next in a capillary in theliver (P-O2=40). When it arrivesat the liver capillaries, thathemoglobin will give up(unbind) O2. Behaves this waybecause of its quaternarystructure D. Conditionsa. Low pHb. More CO2c. Higher temperature the oxygen binding curve of hemoglobin shifts to the rightd. These conditions are likely when cells are doing what?e. This shift (Bohr shift) means that in cells the hemoglobin will release (Give up) more O2 under which conditions 1. pH 7.62. pH 7.2 (correct) E. Fetal hemoglobin binds O2 molecules differently than adult hemoglobin (curve is left-shifted) a. Placenta p-O2 ~ 30 mm Hg, O2 diffuses between maternal and fetal bloodb. Advantage: binds more to the fetal than to the
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