Respiration and Gas exchange

1. Respiration and Gas exchange

2. Key concepts • Types of respiration • Cellular Respiration is the chemical breakdown of food substances to yield ATP. • Different organisms use different kinds of breathing mechanisms in order to transport oxygen throughout their bodies. • Evolutionary adaptations of gas exchange systems and respiration • Different plant adaptations in acquiring CO2 from the environment evolved: C3, C4, and CAM pathways. • Structural adaptations of respiratory apparatus depend on the animal’s habitat. The three most common respiratory organs are gills, tracheae, and lungs. • The respiratory system and circulatory system cooperate directly with each other. • Mammalian respiration • The respiratory system is divided into the upper respiratory tract (nasal passages, mouth, throat, larynx and trachea) and lower respiratory tract (bronchi and the lungs). • Air enters (inhalation) the respiratory system due to a pressure drop inside the lungs (negative pressure). • Air exits (exhalation) the respiratory system due to an increase in pressure inside the lungs. • Breathing is regulated by control centers in the brain (medulla oblongata and pons) • Gases are transported via passive diffusion throughout the body. • Respiratory diseases and their prevention • Respiratory disorders may be congenital or environmental. • Respiratory disorders can be prevented through a combination of proper diet and lifestyle change.

3. Vocabulary words • pneumonia • pons • positive pressure breathing • residual volume • respiratory medium • respiratory pigments • respiratory surface • rib muscles • spiracle • surface tension • syrinx • thoracic cavity • tidal volume • trachea or windpipe • tracheae • tuberculosis • ventilation • vital capacity • vocal cords of the larynx • emphysema • epiglottis • gas exchange • gills • glottis • glycolysis • hemocyanin • hemoglobin • larynx (voicebox) • lung Cancer • lungs • medulla oblongata • myoglobin • nasal cavity • negative pressure breathing • nose • parabronchi • partial pressure • pharynx • photosynthesis • aerobic respiration • air sacs • alveolus • anaerobic respiration • asthma • blood pH • Bohr shift • breathing • bronchiole • bronchus • C3 pathway • C4 pathway • CAM pathway • cell respiration • countercurrent exchange • cutaneous respiration • diaphragm • dissociation curve

4. Cellular Respiration- Transformation of chemical energy into ATP- Overall Reaction: C6H12O6 +6O2 → 6CO2 +6H2O + 36 ATP

5. NADH and FADH2 are e- donors that enable the formation of ATP

6. Photosynthesis • Method of converting sun energy into chemical energy usable by cells • Light reactions • Dark reactions/Calvin Cycle 6 CO2 + 6 H2O + light energy → C6H12O6 + 6O2

7. Plant adaptations for acquiring CO2 from the environment • C3 (most abundant) • CO2 converted to a 3C sugar, 3-phosphoglycerate • RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) enzyme catalyzes carbon fixation • prone to photorespiration, lessens efficiency of food production during hot and dry days • C4 • store CO2 in specialized compartments • convert CO2 into a 4C compound, oxaloacetate • converted into the 3C sugar and CO2 used in the C3 pathway/Calvin cycle • minimizes photorespiration and enhances sugar production • CAM • succulent plants • f ix CO2 at night and store it as 4C organic acids • minimizes water loss and enhances sugar production

9. Gas exchange supplies oxygen for cellular respiration and removes CO2 • Gas exchange – uptake of O2 from environment and discharge of CO2 • Mitochondria need O2 to produce more ATP, CO2 is the by-product C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP • Diffusion rate • α SA  large • α 1/d2  thin • Moist so gases are dissolved first DIFFUSION

10. Respiratory surfaces and gas exchange • Respiratory surface • Size of organism • Habitat • Metabolic demands • Unicellular organisms • Entire surface area for diffusion • Simple invertebrates • Sponges, cnidarians, flatworms, roundworms • diffusion

11. Respiratory surfaces and gas exchange • More complex animals • Thin, moist epithelium • Separates medium from capillaries • Entire outer skin small, long, thin organisms • Specialized respiratory organs that are extensively folded and branched

12. Gills in aquatic animals • Outfoldings of the body surface suspended in water • Sea stars • Segmented worms or polychaetes • Molluscs and crustaceans • Fishes • Young amphibians • Total surface area is greater than the rest of the body

13. Water as a respiratory medium Just keep swimming swimmingswimming! • Surfaces are kept moist • O2 concentrations in water are low • Ventilation – increasing flow of respiratory medium over the surface • Countercurrent exchange – process in which two fluids flow in opposite directions, maximizing transfer rates • Why are gills impractical for land animals?

14. Air as a respiratory medium • Air has a higher concentration of O2 • O2 and CO2 diffuse much faster in the air  less ventilation • Difficulty of keeping surface moist • Solution: respiratory infolding inside the body • Tracheal system of insects – network of tubes that bring O2 to every cell Spiracles

15. Lungs • Heavily vascularized invaginations of the body surface restricted to one location • Found in spiders, terrestrial snails, vertebrates • Amphibians supplement lung breathing with skin • Turtles supplement lung breathing with moist surfaces in mouth and anus

16. Mammalian respiration

17. Lung ventilation through breathing • Positive pressure breathing in frogs • “Gulping in” air • Negative pressure breathing in reptiles and mammals • Rib muscles and diaphragm change lung volume and pressure

18. Lung volumes • Factors • Sex • Height • Smoking • Physical activity • Altitude • Tidal volume • Volume of air inhaled and exhaled with each breath • Vital capacity • Maximum volume inhaled and exhaled during forced breathing • Residual volume • Air left in alveoli after forced exhalation

19. Avian breathing • Air sacs - bellows to keep air flowing through the lungs • Syrinx – vocal organ of birds

20. Control centers in the brain regulate breathing

21. Gases diffuse down pressure gradientsconcentration and pressure drives the movement of gases into and out of blood

22. Respiratory pigments • O2 transport • Low solubility of O2 in H2O • Respiratory pigments are proteins with metal atoms • Hemoglobin – Fe • Hemocyanin – Cu • Allow reversible binding of O2 • Drop in pH results in a lowered affinity of hemoglobin for O2

23. Respiratory pigments • CO2 transport • 7% in plasma • 23% bound to hemoglobin • 70% as HCO3- • buffer

24. Fetal hemoglobin HbF has greater affinity 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

25. Deep-diving mammals • Seals, whales, dolphins are capable of long underwater dives • Weddell seal  5% O2 in lungs, 70% in blood • Huge spleen stores huge volumes of blood • Large concentrations of myoglobin in muscles • Heart rate and O2 consumption rate decrease • Blood is redirected from muscles to brain spinal cord and eyes