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Lecture 4

Winter Term -Week 4 Lecture Notes

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BIOL 103
Virginia K Walker

Blood Clotting Cascade Reaction - platelets • Platelets - fragments of cells • Contain actin, therefore can change their shaoe • Congregate together (help with hormone, prostaglandin) • Cyclooxygenase produces prostaglandin and can be inhibited by aspirin (therefore, aspirin thins blood) • Aggregation of platelets produce platelet factor • Platelet factor + Ca helps platelets expand • Prothrombin (zymogen) in bloodstream converts to active form, thrombin • Other clotting factors + platelet factor converts this • Thrombrin (an endoprotease) goes to fibrinogen (inactive) or fibrin (active) • Fibrin + Ca produces fibrin threads, forming a soft clot  mature clot Warfarin – rat poison • Looks like vitamin K, therefore acts as a substrate • Cannot convert vitamin K, therefore decrease probability of clot forming • Cannot convert inactive clotting factors to active clotting factors • Hemorrhages (internal bleeding)  rat dies Red blood cells • Indented shape: o maximize surface area of membrane o no nucleus also contributes to more surface area • type of blood depends on what glycoproteins you have (or a lack thereof) • example question: “Which one of the following are a porphyrin molecule” • About 3 million hemoglobin (4 oxygen in each) in each RBC • Hemoglobin is a tetramer (2 beta and 2 alpha globins) and 4 heme groups; transports oxygen Gas and Gas Pressure • Air is 21% oxygen, 78% nitrogen and 1% other gases (nitrogen not part of respiratory system, so usually ignored in this case) • Atmospheric pressure o 1kPa or 7.5mmHg o Sum of the partial pressure in proportion to their amounts o Ex. PO2 0.21*760mmHg = 160mmHg • Capillaries have low peartial pressure, so it is easier for oxygen to diffuse into tissue • In lungs, oxygen diffuses across the membrane of the alveoli • Release of CO2 from tissue to bloodstream: CO2 + H2O H2CO3 H + HCO3 – o Some carried in plasma o some in RBCs o some combines with oxygen, forming carbonic acid (dissociate to bicarbonate (buffer) and hydrogen) o Hydrogen ion lowers the PH slightly, making the release of oxygen from the RBC easier • (Lungs )O2 +Hb  HbO2 (tissue) reverse from tissue to lungs Altitude sickness • not enough oxygen to the brain because of low atmospheric pressure; disoriented, confusion, death • adaptations: o Increase number of red blood cells (through high-altitude training) o Larger lungs/chest (greater lung capacity) o Ex. lamas have different hemoglobin (100% O2 saturation at less atmospheric pressure) Variability in Hemoglobin • Fetus hemoglobin have greater O2 saturation than adults, because since it’s oxygen source is the placenta (which has lower pressure), its hemoglobin must be able to be at full capacity to compensa
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