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- 1. alveoli Gas Exchange Respiratory Systems elephant gills AP Biology seals 2008-2009
- 2. AP Biology
- 3. respiration for respiration Why do we need a respiratory system? Need O2 in for aerobic cellular respiration make ATP Need CO2 out food waste product from Krebs cycle O2 ATP AP Biology CO2
- 4. Gas exchange O2 & CO2 exchange between environment & cells need moist membrane need high surface area AP Biology
- 5. Optimizing gas exchange Why high surface area? maximizing rate of gas exchange CO & O move across cell membrane by 2 2 diffusion rate of diffusion proportional to surface area Why moist membranes? moisture maintains cell membrane structure gases diffuse only dissolved in water High surface area? High surface area! Where have we heard that before? AP Biology
- 6. Gas exchange in many forms… one-celled amphibians echinoderms cilia insects fish mammals AP Biology size • water vs. land • endotherm vs. ectotherm
- 7. Evolution of gas exchange structures Aquatic organisms external systems with lots of surface area exposed to aquatic environment Terrestrial moist internal respiratory tissues with lots of surface area AP Biology
- 8. Gas Exchange in Water: Gills AP Biology
- 9. Counter current exchange system Water carrying gas flows in one direction, blood flows in opposite direction Why does it work counter current? Adaptation! just keep AP Biology swimming….
- 10. How counter current exchange works 70% 40% front back 100% 15% water 60% 30% 90% counter- 5% current blood 50% 70% 100% 50% 30% water concurrent 5% blood Blood & water flow in opposite directions maintains diffusion gradient over whole length of gill capillary AP Biology maximizing O2 transfer from water to blood
- 11. Gas Exchange on Land Advantages of terrestrial life air has many advantages over water higher concentration of O2 O2 & CO2 diffuse much faster through air respiratory surfaces exposed to air do not have to be ventilated as thoroughly as gills air is much lighter than water & therefore much easier to pump Why don’t expend less energy moving air in & out land animals Disadvantages use gills? keeping large respiratory surface moist causes high water loss reduce water loss by keeping lungs internal AP Biology
- 12. Terrestrial adaptations Tracheae air tubes branching throughout body gas exchanged by diffusion across moist cells lining terminal ends, not through open circulatory system AP Biology
- 13. Exchange tissue: spongy texture, honeycombed Lungs with moist epithelium Why is this exchange with the environment RISKY? AP Biology
- 14. Alveoli Gas exchange across thin epithelium of millions of alveoli total surface area in humans ~100 m2 AP Biology
- 15. Negative pressure breathing Breathing due to changing pressures in lungs air flows from higher pressure to lower pressure pulling air instead of pushing it AP Biology
- 16. Mechanics of breathing Air enters nostrils filtered by hairs, warmed & humidified sampled for odors Pharynx → glottis → larynx (vocal cords) → trachea (windpipe) → bronchi → bronchioles → air sacs (alveoli) Epithelial lining covered by cilia & thin film of mucus mucus traps dust, pollen, particulates ded to see this picture. beating cilia move mucus upward ompressed) decompressor QuickTime™ and a to pharynx, where it is swallowed AP Biology
- 17. don’t want to have to think Autonomic breathing control to breathe! Medulla sets rhythm & pons moderates it coordinate respiratory, cardiovascular systems & metabolic demands Nerve sensors in walls of aorta & carotid arteries in neck detect O2 & CO2 in blood AP Biology
- 18. Medulla monitors blood Monitors CO2 level of blood measures pH of blood & cerebrospinal fluid bathing brain CO2 + H2O → H2CO3 (carbonic acid) if pH decreases then increase depth & rate of breathing & excess CO2 is eliminated in exhaled air AP Biology
- 19. Breathing and Homeostasis ATP Homeostasis keeping the internal environment of the body balanced need to balance O2 in and CO2 out need to balance energy (ATP) production Exercise breathe faster O2 CO2 need more ATP bring in more O2 & remove more CO2 Disease poor lung or heart function = breathe faster need to work harder to bring in O2 & remove CO2 AP Biology
- 20. Diffusion of gases Concentration gradient & pressure drives movement of gases into & out of blood at both lungs & body tissue capillaries in lungs capillaries in muscle O2 O2 O2 O2 CO2 CO2 CO2 CO2 blood lungs blood body AP Biology
- 21. Hemoglobin Why use a carrier molecule? O2 not soluble enough in H2O for animal needs blood alone could not provide enough O2 to animal cells hemocyanin in insects = copper (bluish/greenish) hemoglobin in vertebrates = iron (reddish) Reversibly binds O2 loading O2 at lungs or gills & unloading at cells heme group AP Biology cooperativity
- 22. Cooperativity in Hemoglobin Binding O2 binding of O2 to 1st subunit causes shape change to other subunits conformational change increasing attraction to O2 Releasing O2 when 1st subunit releases O2, causes shape change to other subunits conformational change lowers attraction to O2 AP Biology
- 23. O2 dissociation curve for hemoglobin Effect of pH (CO2 concentration) Bohr Shift drop in pH 100 pH 7.60 90 % oxyhemoglobin saturation lowers affinity pH 7.40 pH 7.20 80 of Hb for O2 70 active tissue 60 50 (producing 40 CO2) lowers 30 More O2 delivered to tissues blood pH 20 & induces Hb 10 0 to release 0 20 40 60 80 100 120 140 more O2 PO2 (mm Hg) AP Biology
- 24. O2 dissociation curve for hemoglobin Effect of Temperature Bohr Shift 100 increase in 90 20°C % oxyhemoglobin saturation 37°C temperature 80 43°C lowers affinity 70 of Hb for O2 60 50 active muscle 40 produces heat 30 More O2 delivered to tissues 20 10 0 0 20 40 60 80 100 120 140 PO2 (mm Hg) AP Biology
- 25. Transporting CO2 in blood Dissolved in blood plasma as bicarbonate ion Tissue cells carbonic acid CO2 + H2O → H2CO3 CO2 carbonic anhydrase Carbonic anhydrase CO2 dissolves in plasma bicarbonate CO2 + H2O H2CO3 H2CO3 H2CO3 → H+ + HCO3– CO2 combines H+ + HCO3– with Hb Cl– HCO3– Plasma AP Biology
- 26. Releasing CO2 from blood at lungs Lower CO2 Lungs: Alveoli pressure at lungs allows CO2 to diffuse out of CO2 blood into lungs CO2 dissolved in plasma CO2 + H2O H2CO3 HCO3 – + H+ Hemoglobin + CO2 H2CO3 HCO3–Cl– AP Biology Plasma
- 27. Adaptations for pregnancy Mother & fetus exchange Why would mother’s Hb give up O2 & CO2 across placental its O2 to baby’s Hb? tissue QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. AP Biology
- 28. Fetal hemoglobin (HbF) HbF has greater attraction to O2 than Hb low % O2 by time blood reaches placenta fetal Hb must be able to bind O2 with greater attraction than maternal Hb What is the adaptive advantage? AP Biology 2 alpha & 2 gamma units
- 29. Don’t be such a baby… Ask Questions!! AP Biology 2008-2009
Editor's Notes
- #6: small intestines large intestines capillaries mitochondria
- #8: Constantly passing water across gills Crayfish & lobsters paddle-like appendages that drive a current of water over their gills Fish creates current by taking water in through mouth, passes it through slits in pharynx, flows over the gills & exits the body
- #9: In fish, blood must pass through two capillary beds, the gill capillaries & systemic capillaries. When blood flows through a capillary bed, blood pressure — the motive force for circulation — drops substantially. Therefore, oxygen-rich blood leaving the gills flows to the systemic circulation quite slowly (although the process is aided by body movements during swimming). This constrains the delivery of oxygen to body tissues, and hence the maximum aerobic metabolic rate of fishes.
- #10: Living in water has both advantages & disadvantages as respiratory medium keep surface moist O 2 concentrations in water are low, especially in warmer & saltier environments gills have to be very efficient ventilation counter current exchange
- #13: How is this adaptive? No longer tied to living in or near water. Can support the metabolic demand of flight Can grow to larger sizes.
- #14: Lungs, like digestive system, are an entry point into the body lungs are not in direct contact with other parts of the body circulatory system transports gases between lungs & rest of body
- #22: The low solubility of oxygen in water is a fundamental problem for animals that rely on the circulatory systems for oxygen delivery. For example, a person exercising consumes almost 2 L of O 2 per minute, but at normal body temperature and air pressure, only 4.5 mL of O 2 can dissolve in a liter of blood in the lungs. If 80% of the dissolved O 2 were delivered to the tissues (an unrealistically high percentage), the heart would need to pump 500 L of blood per minute — a ton every 2 minutes.
- #29: Both mother and fetus share a common blood supply. In particular, the fetus's blood supply is delivered via the umbilical vein from the placenta, which is anchored to the wall of the mother's uterus. As blood courses through the mother, oxygen is delivered to capillary beds for gas exchange, and by the time blood reaches the capillaries of the placenta, its oxygen saturation has decreased considerably. In order to recover enough oxygen to sustain itself, the fetus must be able to bind oxygen with a greater affinity than the mother. Fetal hemoglobin's affinity for oxygen is substantially greater than that of adult hemoglobin. Notably, the P50 value for fetal hemoglobin (i.e., the partial pressure of oxygen at which the protein is 50% saturated; lower values indicate greater affinity) is roughly 19 mmHg, whereas adult hemoglobin has a value of approximately 26.8 mmHg. As a result, the so-called "oxygen saturation curve", which plots percent saturation vs. pO2, is left-shifted for fetal hemoglobin in comparison to the same curve in adult hemoglobin. Hydroxyurea, used also as an anti-cancer drug, is a viable treatment for sickle cell anemia, as it promotes the production of fetal hemoglobin while inhibiting sickling.