IB Biology SL B3.1 Gas exchange Questions

ventilation is moving air into and out of lungs/inhalation and exhalation;
involves (respiratory) muscle activity;
gas exchange involves movement of carbon dioxide and oxygen;
between alveoli and blood (in capillaries) / between blood (in capillaries) and cells;
cell respiration is the release of energy from organic molecules/glucose;
(aerobic) cell respiration occurs in mitochondria;

To award [4 max] responses must address ventilation, gas exchange and cell respiration.

a. $\mathrm{O}_{2}$ diffuses into blood and $\mathrm{CO}_{2}$ diffuses out from blood

b. blood entering the alveoli is high in $\mathrm{CO}_{2}$ /low in $\mathrm{O}_{2}$

OR

air in alveolus is high in $\mathrm{O}_{2}$ /low in $\mathrm{CO}_{2}$

c. diffusion (in either direction) take place due to concentration gradients

d. concentration gradients maintained by ventilation/blood flow

e. large surface area created by many alveoli/spherical shape of alveoli for more efficient diffusion

f. rich supply of capillaries (around alveoli) allows efficient exchange

g. type I pneumocytes are thin to allow easy diffusion/short distances

h. gases must dissolve in liquid lining of alveolus in order to be exchanged

i. type II pneumocytes secrete surfactants to reduce surface tension/prevent lungs sticking together

j. type II pneumocytes create moist conditions in alveoli

Explain

7 max

exercise increases the need for oxygen (to muscular tissue);
increase in volume allows more air / oxygen in lungs;
increase in ventilation rate allows more gas exchange/oxygen and carbon dioxide to be exchanged;
increase in ventilation volume/rate allows more oxygen in blood (to meet increased muscle need);
sufficient oxygen allows aerobic respiration/prevents oxygen debt / insufficient oxygen means anaerobic respiration;

A

C

D

C

(count) number of stomata (within field of view / image) AND divide by the area / field of view;