1. Essentials of the Living World Second Edition George B. Johnson Jonathan B. Losos Chapter 26 Respiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 26.1 Types of Respiratory Systems Respiration is the uptake of oxygen and the simultaneous release of carbon dioxide  most primitive animal phyla obtain oxygen directly from their environments through diffusion  more advanced phyla have specific respiratory organs gills, tracheae, and lungs

3. Figure 26.1 Gas exchange in animals

4. 26.2 Respiration in Aquatic Vertebrates Water always moves past a fish’s gills in one direction  moving the water past the gills in the same direction permits countercurrent flow this process is an extremely efficient way of extracting oxygen blood flows through a gill filament in an opposite direction to the movement of water the blood in the blood vessels always encounters water with a higher oxygen concentration, resulting in the diffusion of oxygen into the blood vessels

5. Figure 26.2 Structure of a fish gill

6. Figure 26.3 Countercurrent flow

7. 26.3 Respiration in Terrestrial Vertebrates Lungs are less efficient than gills because new air that is inhaled mixes with old air already in the lung  but there is so much more oxygen in air than in water  the lungs of mammals possess on their inner surface many small chambers called alveoli, which greatly increases surface area for the diffusion of oxygen

8. Figure 26.4 Evolution of the vertebrate lung

9. 26.3 Respiration in Terrestrial Vertebrates Flying creates a respiratory demand for oxygen that exceeds the capacity of the saclike lungs of even the most active mammal  birds have evolved the most efficient lung an avian lung is connected to a series of air sacs outside of the lung birds have unidirectional flow of air through the lungs blood flow and air flow are not opposite but flow at perpendicular angles in crosscurrent flow

10. Figure 26.5 How a bird breathes

11. 26.4 The Mammalian Respiratory System The mammal respiratory apparatus is simple in structure and function as a one-cycle pump  a diaphragm muscle separates the thoracic cavity from the abdominal cavity  each lung is covered by a thin, smooth membrane called the pleural membrane  this membrane adheres to another pleural membrane lining the walls of the thoracic cavity, basically coupling the lungs to the thoracic cavity  air is drawn into the lungs by the creation of negative pressure

12. 26.4 The Mammalian Respiratory System The active pumping of air in and out is called breathing  during inhalation, muscular contraction causes chest cavity to expand  during exhalation, the ribs and diaphragm return to their original position

13. Figure 26.7 How breathing works

14. 26.4 The Mammalian Respiratory System In a human a typical breath at rest moves about 0.5 L of air, called the tidal volume The extra amount that can be forced into and out of the lung is called the vital capacity and is about 4.5 L in men and 3.1 L in women The air remaining in the lung after such a maximal expiration is the residual volume, or dead volume, typically about 1.2 L

15. 26.5 How Respiration Works: Gas Exchange Oxygen moves through the circulatory system piggyback on the protein hemoglobin  hemoglobin molecules contain iron and oxygen binds in a reversible way Figure 26.8 The hemoglobin molecule

16. 26.5 How Respiration Works: Gas Exchange hemoglobin molecules act like little sponges for oxygen  at the high O 2 levels that occur in the blood supply at the lung, most hemoglobin carry a full load of O 2  in the tissues, the O 2 levels are much lower so that hemoglobin gives up its bound oxygen  in the presence of CO 2, the hemoglobin assumes a different shape that give up its oxygen more readily

17. 26.5 How Respiration Works: Gas Exchange CO 2 must also be transported by the blood  about 8% simply dissolves in the plasma  20% is bound to hemoglobin but at a different site than what O 2 binds to  the remaining 72% diffuses into the red blood cells In order to maintain the gradient for CO 2 to leave the tissues and enter the plasma, the CO 2 levels in the plasma must be kept low

18. 26.5 How Respiration Works: Gas Exchange The enzyme carbonic anhydrase combines CO 2 with water to form carbonic acid (H 2 CO 3 )  this acid dissociates into bicarbonate (HCO 3 - ) and H +  the H + binds to hemoglobin while the red blood cell moves the bicarbonate out into the plasma the protein that moves the bicarbonate out exchanges it for a chloride this exchange is known as the chloride shift

19. Figure 26.9 How respiratory gas exchange works

20. 26.5 How Respiration Works: Gas Exchange Hemoglobin has the ability to hold and release the gas nitric oxide (NO)  NO has an important physiological role in the body, acting on many kinds of cells to change their shape and function for example, NO causes blood vessels to expand because it relaxes the surround muscle cells

21. 26.6 The Nature of Lung Cancer Smoking causes lung cancer  it causes mutations to certain tumor- suppressing genes Rb codes for Rb protein, which acts as a brake on cell division p53 codes for p53 protein, which detects damaged or foreign DNA and prevents it replication

22. Figure 26.11 Incidence of lung cancer in men and women

23. Inquiry & Analysis At an elevation of 5000 feet, the partial pressure of O 2 is 50mm Hg. At this elevation, how much of human hemoglobin has succeeded in binding? of llama? of vicuna? Graphs