Biology 103 - Main points/Questions

1. Biology 103 - Main points/Questions How do your lungs work? How do gasses get to your cells? What gasses do plant cells need to transport?

2. Remember Circulation … • Plants and animals push extracellular fluids • Plants generate flow w/o muscle tissue • Animals generate flow with pumping muscles • Fungi move intracellular fluids • Use cytoplasmic streaming • Proteins in the cell “stir” the cytoplasm moving nutrients etc. to rapidly growing hyphae. • Protists use diffusion & streaming

3. Why exchange gases? Cellular respiration - summarized as: • Glucose + oxygen  carbon dioxide + water • Look! This consumes oxygen and gives off CO2 • And, of course, produces ATP! • So - Gas exchange supplies oxygen for cellular respiration and disposes of carbon dioxide

4. Gas Exchange • All the complex multicellular critters use oxygen to produce ATP in mitochondria • So all cells need gas exchange for this • Many plant cells also need a supply of carbon dioxide for photosynthesis • We look at animals first

5. Gas exchange occurs between an organism and the environment, often in specialized respiratory organs. In vertebrates gases are transferred via the circulatory system!

6. Ultimately exchange happens between cells and the interstitial fluid that surrounds them!

7. Types of Respiratory Systems • The simplest animals obtain oxygen directly from their environments through diffusion

8. Fig. 40-3 Mouth Diffusion works well as long as distances are small and surfaces are permeable Gastrovascular cavity But as organisms become more complex they need specialized exchange organs Exchange Exchange Exchange 1.5 mm (a) Single cell Cnidarians

9. Fig. 40-3 Mouth Diffusion works well as long as distances are small and surfaces are permeable All organisms use diffusion at the cellular level but… Gastrovascular cavity Exchange Exchange Exchange 1.5 mm (a) Single cell Cnidarians

10. Types of Respiratory Systems • As organisms get more complex they need specialized organs to exchange gases with the environment • different phyla have different organs: • Gills in fish, some arthropods, mollusks, • Tracheae in insects, • and lungs mostly in terrestrial chordates

11. Why do gases move? Gases diffuse down pressure gradients in the lungs and other organs In the lungs and tissues, O2 and CO2 diffuse from where their concentrations are higher to where they are lower

12. Remember diffusion • Movement from high concentration to low • Doesn’t require any energy expenditure to make happen • Works very quickly over short distances • Important transport mechanism of cellular material

13. Factors controlling diffusion rate: • Can you remember what some are?

14. Factors controlling diffusion rate: • set by organism • set • constantly maintained • Increased as much as possible • Decrease as much as possible • Gas as often as possible • Temperature • Size of molecule: • Concentration gradient: • Surface area: • Distance: • Medium

15. Respiratory Medium • Animals can use air or water as a source of O2, or respiratory medium • In a given volume, there is less O2 available in water than in air • Obtaining O2 from water requires greater efficiency than air breathing

16. Respiration in Aquatic Vertebrates • Water moves past a fish’s gills in one direction • this permits countercurrent flow

17. Respiration in Aquatic Vertebrates • Countercurrent flow • extremely efficient way of extracting oxygen • blood flows through a gill filament in an opposite direction to the movement of water • the blood always encounters water with a higher oxygen concentration (constant gradient for diffusion)

18. Because the two fluids flow in opposite directions blood can continue to pick up oxygen well past the 50% mark. Figure 30.3 Countercurrent flow

19. If blood flowed in the same direction as water the system could exchange at most 50% of the gas dissolved. Figure 30.3 Countercurrent flow

20. Terrestrial gas exchange • For organisms on the land gas exchange poses a new problem • The exchange must happen on living cells bathed in fluid – but fluid loss can be a huge problem so… • Gas exchange organs are moved into the body & adaptations to prevent water loss are common.

21. Tracheal Systems in Insects • The tracheal system of insects consists of tiny branching tubes that penetrate the body • The tracheal tubes supply O2 directly to body cells

22. Fig. 30.1.c

23. Lungs • Lungs - an infolding of the body surface • The circulatory system transports gases between the lungs and the body • The size and complexity of lungs correlate with an animal’s metabolic rate

24. In humans: • A system of branching ducts conveys air to the lungs • Air inhaled through the nostrils passes through the pharynx via the larynx, trachea, bronchi, bronchioles, and alveoli, where gas exchange occurs • Exhaled air passes over the vocal cords and cancreate sounds

25. Fig. 30.6

26. Fig. 30.4.c

27. How a Mammal Breathes • Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs • Lung volume increases as the rib muscles and diaphragm contract

28. Figure 30.7 How breathing works

29. Blood arriving in the lungs has a low amount of O2 and a high concentration of CO2 relative to air in the alveoli • In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air • In tissue capillaries, gradients favor diffusion of O2 into the interstitial fluids and CO2 into the blood

30. Alveolus Alveolus PCO2 = 40 mm Hg PO2 = 100 mm Hg PCO2 = 46 PO2 = 40 PCO2 = 40 PO2 = 100 • Blood arriving in the lungs has a low O2 and a high CO2 relative to air in the alveoli • When it leaves this has reversed • Then in body tissue the situation is the opposite Circulatory system Circulatory system PO2 = 40 PO2 = 100 PCO2 = 40 PCO2 = 46 PO2 ≤ 40 mm Hg PCO2 ≥ 46 mm Hg Body tissue Body tissue (a) Oxygen (b) Carbon dioxide

31. Alveolus Alveolus PCO2 = 40 mm Hg PO2 = 100 mm Hg PO2 = 40 PCO2 = 46 PCO2 = 40 PO2 = 100 Circulatory system Circulatory system PO2 = 40 PO2 = 100 PCO2 = 40 PCO2 = 46 • In tissue capillaries, O2 moves out of the blood and CO2 moves into the blood… why? • To move more gas they are carried in several ways PO2 ≤ 40 mm Hg PCO2 ≥ 46 mm Hg Body tissue Body tissue

32. hemoglobin molecules contain iron - oxygen binds in a reversible way Figure 30.8 The hemoglobin molecule

33. hemoglobin acts like little sponges for oxygen • at high O2 levels (like in the lungs), most hemoglobin carry a full load of O2 • in the tissues, the O2 levels are much lower and hemoglobin gives up its bound oxygen • The vast majority (> 90%) of oxygen you use was carried to your cells on hemoglobin

34. CO2 must also be transported by the blood • about 8% simply dissolves in the plasma • 20% is bound to hemoglobin • rest is carried as HCO3- in blood cells & plasma • This is highlighted on figure from your book…

35. Figure 30.9 How respiratory gas exchange works

36. CO2 O2 Light Sugar H2O • What about plants? Do they transport gasses in circulatory system? • No! – they rely only on diffusion • specialized anatomy makes this work… O2 H2Oand minerals CO2

37. Leaf cross section shows… • Cells packed in top layer - photosynthesis • Open “spongy” layer below for exchange • But cuticle blocks gas exchange…

38. Plant leaf anatomy: • Lots of open spaces inside but… • Must open stomata (pores) to get gasses in Opened Closed

39. This causes leaf to lose water so… • plants need to balance water loss and gas exchange • Guard cells control opening/closing • How…? • changes in the water pressure of guard cells

40. Figure 23.20 - guard cells open and close stomata • When the guard cells are plump and swollen with water, they are said to be turgid and the stoma is open • When the guard cells lose water, the stoma closes

41. Controlling stomata opening: • Most plants keep closed at night open during the day. Why? • Some specially adapted plants keep closed during day & open at night… Why would you do that? • Hint: ➔