IB Biology HL B3.1 Gas Exchange Question Bank
Practise IB Biology HL B3.1 by linking respiratory surfaces and ventilation to oxygen transport, dissociation curves and transpiration evidence.
- Syllabus
- First assessment 2025
- Course
- Biology HL
- Level
- HL
Exam points
- link surface area, diffusion distance, permeability and moisture to efficient gas exchange
- explain how ventilation and blood flow maintain oxygen and carbon-dioxide gradients
- interpret spirometry and pressure-volume changes during inspiration and expiration
- explain stomatal control, leaf adaptations and environmental effects on transpiration
- interpret oxygen dissociation curves, cooperative binding and Bohr shifts to predict oxygen loading and unloading
Covered syllabus points
B3.1.1—Gas exchange as vital functionB3.1.2—Properties of gas-exchange surfacesB3.1.3—Maintaining concentration gradientsB3.1.4—Mammalian lung adaptationsB3.1.5—Lung ventilationB3.1.6—Lung volume measurementsB3.1.7—Leaf gas exchange adaptationsB3.1.8—Leaf tissue distributionB3.1.9—TranspirationB3.1.10—Stomatal densityB3.1.11 (HL)—Haemoglobin adaptationsB3.1.12 (HL)—Bohr shiftB3.1.13 (HL)—Oxygen dissociation curves
B3.1 Gas exchange question 1
[Maximum number: 3]
Outline the process of gas exchange necessary for aerobic respiration in a unicellular eukaryotic organism.
a. oxygen must be taken up AND carbon dioxide must be released
b. gases pass through a cell membrane by simple diffusion
c. require a concentration gradient
OR pass from high concentration to low concentration
d. without requiring energy
OR passive process
e. large SA: vol ratio
Both needed.
3 max
Question
Answers
Notes
Total
B3.1 Gas exchange question 2
[Maximum number: 3]
Carbon dioxide and oxygen are essential gases in many biological processes.
Describe conditions necessary in the lungs for efficient gas exchange in humans.
a. alveoli provide a large surface area (for easy diffusion of gases);
b. thin walls/ 1 -cell thick walls /type 1 pneumocytes/cells lining the alveoli are (extremely) thin (to facilitate gas exchange);
c. a moist surface on the cells (to dissolve the gases/oxygen and carbon dioxide);
d. type II pneumocytes secrete surfactant to reduce surface tension/prevent sides of alveolus sticking together;
e. blood capillaries have thin walls/1-cell thick walls (for short path/easy diffusion of gases);
f. good supply of blood / blood flow through capillaries around alveoli to maintain the concentration gradients of gases/ higher oxygen concentration in alveoli than in blood capillaries/ higher CO2 concentration in blood capillaries that in alveoli;
g. ventilation/breathing maintains concentration gradients of gases (between air in alveoli and blood capillaries) (to facilitate diffusion);
Mpb. Refers to thin walls, not membranes.
Mpd. Requires function of surfactant.
3 marks
B3.1 Gas exchange question 3
[Maximum number: 7]
Adult humans may absorb more than five hundred litres of oxygen per day. Explain how gas exchange is maintained in the human respiratory system.
a. ventilation/inhaling brings fresh air/air with high oxygen concentration to the lungs OR ventilation/exhaling gets rid of stale air/air with high concentration of carbon dioxide
b. ventilation due to muscle contractions causing pressure/volume changes in the thorax
c. contraction of external intercostal muscles AND diaphragm occurs during inspiration OR contraction of internal intercostal muscles/abdomen wall muscles during «forced» expiration
d. alveoli surrounded by «many» capillaries
e. blood flow/pumping of heart «brings blood to/takes blood away from alveoli/lungs»
f. concentration gradients «of oxygen/ CO2 » maintained «by ventilation/blood flow»
g. O2 AND CO2 diffuse
h. CO2 from capillaries/blood/vessel to alveolus/air AND O2 from alveoli into capillaries/blood/vessel
i. large numbers of alveoli increase surface area
j. short distance so rapid diffusion/gas exchange
k. type I pneumocytes/alveolus wall/capillary walls are one cell thick/very thin
I. alveoli «lining» moist for dissolving of gases/rapid diffusion OR
type II pneumocytes keep the «lining of» the alveolus moist
m. type II pneumocytes secrete surfactant to reduce surface tension/prevents alveoli from collapsing
7 max
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