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AP Biology Why do we need a respiratory system? O2O2 food ATP CO 2 Need O 2 in for aerobic cellular respiration make ATP Need CO 2 out waste product from Krebs cycle
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AP Biology Optimizing gas exchange High surface area maximizing rate of gas exchange CO 2 & O 2 move across cell membrane by diffusion rate of diffusion proportional to surface area Moist membranes moisture maintains cell membrane structure gases diffuse only dissolved in water
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AP Biology Gas exchange in many forms… one-celledamphibiansechinoderms insectsfishmammals endotherm vs. ectotherm size cilia water vs. land
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AP Biology Counter current exchange system Water carrying gas flows in one direction, blood flows in opposite direction
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AP Biology Blood & water flow in opposite directions maintains diffusion gradient over whole length of gill capillary maximizing O 2 transfer from water to blood water blood How counter current exchange works front back blood 100% 15% 5% 90% 70%40% 60%30% 100% 5% 50% 70% 30% water counter- current concurrent
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AP Biology Gas Exchange on Land Advantages of terrestrial life air has many advantages over water higher concentration of O 2 O 2 & CO 2 diffuse much faster through air air is much lighter than water & therefore much easier to pump Disadvantages keeping large respiratory surface moist causes high water loss Internal lungs
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AP Biology Terrestrial adaptations air tubes branching throughout body gas exchanged by diffusion across moist cells Tracheae
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Lungs Exchange tissue: spongy texture, moist epithelium Air enters nostrils Pharynx glottis larynx (vocal cords) trachea (windpipe) bronchi bronchioles air sacs (alveoli) Epithelial lining covered by cilia & thin film of mucus
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AP Biology Alveoli Gas exchange across thin epithelium of millions of alveoli total surface area in humans ~100 m 2
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AP Biology Negative pressure breathing Breathing due to changing pressures in lungs pulling air instead of pushing it
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Autonomic breathing control Medulla sets rhythm & pons moderates it measures pH of blood & cerebrospinal fluid bathing brain CO 2 + H 2 O H 2 CO 3 (carbonic acid) if pH decreases then increase rate of breathing & excess CO 2 is eliminated in exhaled air Nerve sensors in walls of aorta & carotid arteries in neck detect O 2 & CO 2 in blood
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AP Biology Diffusion of gases Concentration gradient & pressure drives movement of gases into & out of blood at both lungs & body tissue bloodlungs CO 2 O2O2 O2O2 bloodbody CO 2 O2O2 O2O2 capillaries in lungscapillaries in muscle
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AP Biology Hemoglobin Why use a carrier molecule? O 2 not soluble enough in H 2 O for animal needs hemocyanin in insects = copper (bluish/greenish) hemoglobin in vertebrates = iron (reddish) Reversibly binds O 2 loading O 2 at lungs or gills & unloading at cells cooperativity heme group
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AP Biology Cooperativity in Hemoglobin Binding O 2 binding of O 2 to 1 st subunit causes shape change to other subunits conformational change increasing attraction to O 2 Releasing O 2 when 1 st subunit releases O 2, causes shape change to other subunits conformational change lowers attraction to O 2
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AP Biology O 2 dissociation curve for hemoglobin Bohr Shift drop in pH lowers affinity of Hb for O 2 active tissue (producing CO 2 ) lowers blood pH & induces Hb to release more O 2 P O 2 (mm Hg) 0 10 20 30 40 50 60 70 80 90 100 020406080100120140 More O 2 delivered to tissues pH 7.60 pH 7.20 pH 7.40 % oxyhemoglobin saturation Effect of pH (CO 2 concentration)
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AP Biology O 2 dissociation curve for hemoglobin Bohr Shift increase in temperature lowers affinity of Hb for O 2 active muscle produces heat P O 2 (mm Hg) 0 10 20 30 40 50 60 70 80 90 100 020406080100120140 More O 2 delivered to tissues 20°C 43°C 37°C % oxyhemoglobin saturation Effect of Temperature
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AP Biology Transporting CO 2 in blood Tissue cells Plasma CO 2 dissolves in plasma CO 2 combines with Hb CO 2 + H 2 OH 2 CO 3 H+ + HCO 3 – HCO 3 – H 2 CO 3 CO 2 Carbonic anhydrase Cl– Dissolved in blood plasma as bicarbonate ion carbonic acid CO 2 + H 2 O H 2 CO 3 bicarbonate H 2 CO 3 H + + HCO 3 – carbonic anhydrase
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AP Biology Releasing CO 2 from blood at lungs Lower CO 2 pressure at lungs allows CO 2 to diffuse out of blood into lungs Plasma Lungs: Alveoli CO 2 dissolved in plasma HCO 3 – Cl – CO 2 H 2 CO 3 Hemoglobin + CO 2 CO 2 + H 2 O HCO 3 – + H +
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