AP Biology D.N.A Objective: SWBAT describe the movement of air through air passageways to the alveolus, listing the structures that air must pass through on its journey. 1. In humans, most nutrient molecules are absorbed by the _______________ 2. It is sometimes necessary to remove a diseased portion of the digestive system, but usually a patient can get along on a modified diet. It would be most likely to live without which of the following and WHY? Stomach, large intestine, gallbladder, small intestine, salivary gland.

AP Biology gills alveoli elephant seals Gas Exchange Respiratory Systems

AP Biology Why do we need a respiratory system? O2O2 food ATP CO 2 respiration for respiration  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

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 Counter current exchange system  Water carrying gas flows in one direction, blood flows in opposite direction just keep swimming…. Why does it work counter current? Adaptation!

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 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 Why don’t land animals use gills?

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 Why is this exchange with the environment RISKY?

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

AP Biology 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  beating cilia move mucus upward to pharynx, where it is swallowed

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 don’t want to have to think to breathe! 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)  The pH starts to drop when the amount of CO2 increases in the blood  EX: Exercise exerts more CO2 as a waste product  Acid lowers the pH of the blood  Medulla senses this pH drop, and increases breathing rate

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 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 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 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 Adaptations for pregnancy  Mother & fetus exchange O 2 & CO 2 across placental tissue Why would mother’s Hb give up its O 2 to baby’s Hb?

AP Biology Fetal hemoglobin (HbF) What is the adaptive advantage? 2 alpha & 2 gamma units  HbF has greater attraction to O 2 than Hb  low % O 2 by time blood reaches placenta  fetal Hb must be able to bind O 2 with greater attraction than maternal Hb