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

AP Biology Gas exchange  O 2 & CO 2 exchange between environment & cells  need moist membrane  need high surface area  Why?

AP Biology Optimizing gas exchange  Why 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  Why moist membranes?  moisture maintains cell membrane structure  gases diffuse only dissolved in water

AP Biology Gas exchange in many forms… one-celledamphibiansechinoderms insectsfishmammals endotherm vs. ectotherm size cilia water vs. land

AP Biology Evolution of gas exchange structures external systems with lots of surface area exposed to aquatic environment Aquatic organisms moist internal respiratory tissues with lots of surface area Terrestrial

AP Biology Gas Exchange in Water: Gills

AP Biology Counter current exchange system  Water carrying gas flows in one direction, blood flows in opposite direction

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

AP Biology Learning Check  Summarize how the countercurrent system maximizes O 2 movement from water to blood.

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  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  expend less energy moving air in & out  Disadvantages  keeping large respiratory surface moist causes high water loss  reduce water loss by keeping lungs internal

AP Biology Learning Check  Compare/contrast the costs/benefits of terrestrial vs. aquatic gas exchange

AP Biology Terrestrial adaptations  air tubes branching throughout body  gas exchanged by diffusion across moist cells lining terminal ends, not through open circulatory system Tracheae

AP Biology Lungs Exchange tissue: spongy texture, honeycombed with moist epithelium

AP Biology Alveoli  Gas exchange across thin epithelium of millions of alveoli  total surface area in humans ~100 m 2

AP Biology December 9, 2011  Bell Ringer Quiz  Explain the connection between the circulatory system and…  Respiratory System  Digestive System  Excretory System  Objectives  Use a model to explain negative pressure breathing  Differentiate between circulation in various organisms  Homework  Complete a pre-lab for Cardiovascular lab

AP Biology 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 Mechanics of breathing  Air enters nostrils  filtered by hairs, warmed & humidified  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  beating cilia move mucus upward to pharynx, where it is swallowed

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

AP Biology Hemoglobin  Why use a carrier molecule?  O 2 not soluble enough in H 2 O for animal needs  blood alone could not provide enough O 2 to animal cells  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

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

AP Biology Learning Check  Summarize the need for the carrier molecule hemoglobin. Further explain the conformational changes that occur in the presence/absence of O 2.

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) More O 2 delivered to tissues pH 7.60 pH 7.20 pH 7.40 % oxyhemoglobin saturation Effect of pH (CO 2 concentration)

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) More O 2 delivered to tissues 20°C 43°C 37°C % oxyhemoglobin saturation Effect of Temperature

AP Biology Learning Check  How do you think the respiration rate of an animal that is homeostatic with its environment changes when there is an increase in surrounding temperature?

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

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 +

AP Biology Breathing and Homeostasis  Homeostasis  keeping the internal environment of the body balanced  need to balance O 2 in and CO 2 out  need to balance energy (ATP) production  Exercise  breathe faster  need more ATP  bring in more O 2 & remove more CO 2  Disease  poor lung or heart function = breathe faster  need to work harder to bring in O 2 & remove CO 2 O2O2 ATP CO 2

AP Biology Autonomic breathing control  Medulla sets rhythm & pons moderates it  coordinate respiratory, cardiovascular systems & metabolic demands  Nerve sensors in walls of aorta & carotid arteries in neck detect O 2 & CO 2 in blood

AP Biology Medulla monitors blood  Monitors CO 2 level of blood  measures pH of blood & cerebrospinal fluid bathing brain  CO 2 + H 2 O  H 2 CO 3 (carbonic acid)  if pH decreases then increase depth & rate of breathing & excess CO 2 is eliminated in exhaled air