Chapter+22

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p. 228 Figure 1 1. The falls and rises in pH are caused by the daily cycle of light and dark, which causes the daily cycle of photosynthesis (PS), which causes the daily cycle of CO2 concentration. Falls: at night, no photosynthesis, so [CO2] rises, pH goes down. 2. Rises: In the day, photosynthesis occurs, lowering the [CO2], which increases the pH. 3. Three days, because there are three peaks and troughs. 4. On a very sunny day, there was more PS, so lower [CO2], higher pH. p. 228, Figure 2 1. A. Answers will vary. When a “line” in the photograph separate white and white (2 alveoli), it represents two gas exchange surfaces. When the line is between white and dark, it represents only one gas exchange surface. Units will be gas exchange surfaces/cm. B. Conclusion: healthy lung tissue has more gas exchange surfaces than emphysema lungs. 2. They feel tired because their cells are not getting enough oxygen. 3. There is a reduced gas exchange surface area, which means there are fewer functioning capillary beds, so the right side of the heart has to pump harder to get the blood through a smaller number of blood vessels.

Data based question p 229


 * 1) The air in the alveoli is mixed with ”old air”. The alveoli are not completely empty between each inhalation.
 * 2) a. 65 mmHg

b. Diffusion of oxygen from the alveoli to the blood. c. i. 24,5 mmHg ii. The air exhaled contains CO2 produced in the cells in cell respiration. CO2 diffuse from the blood into the alveoli due to the conc. difference between the blood and the alveoli, the concentration gradient. The air in the alveoli is then exhaled. d. There is no concentration difference in partial pressure of N2 in the alveoli compared with the air. Equal amount diffuse into and out of the blood.

page 230 1a. 22% increase (75%-53%=22%) b. 13% c. 02% d, 02%

2. At an initial 21%, there is a saturation rate of 53%. There will be a rise of 22% at 24% concentration. the increase then slows to 13%, finally reaching a plateau of 2%. When the breathing air contains a higher concentration of oxygen there is a higher conc of oxygen in the alveoli. Due to this there is a higher concentration gradient between the alveoli and the blood. Diffusion will take place at a faster rate thus increasing the arterial oxygen concentration. 3. No increase on arterial oxygen concentration achieved with higher oxygen concentrations than approx 30%. At this level the blood is almost fully saturated. 4. 30% gives 90% oxygen saturation, and above this there is almost no increase so there is no reason for increasing the oxygen concentration more. Below 30%, 28% the oxygen concentration drops rather fast so it is important to not go below this to achieve 90% saturation. 5. People get addicted to smoking and it is a habit that is very difficult to break. If they have been smoking for a long time they might not understand, or want to understand that it is smoking that causes these effects.

p 231 Rediscover biology: measuring ventilation rate and lung volumes.

1. I = Volume of one “normal “ breath, tidal volume. II = Maximum volume of max inhalation and max exhalation, vital capacity. III = volume of air left in lungs after max exhalation, residual volume. IV = total volume of lungs. 2. It is difficult to know the tidal volume, and very difficult to measure this volume since we never empty our lungs completely. 3. Breathing rate. 4. Long volume varies. Lung volume is dependent on gender, height, body shape, physical fitness, activities such as playing the trumpet, singing, diving, swimming, smoking, disease such as COPD, asthma.