IB DP Biology Topic 6: Human physiology : 6.4 Gas exchange Question Bank SL Paper 1

IB Biology SL (Standard level)- 2024 – Practice Questions- All Topics

Topic 6.4 Gas exchange

Topic 6 Weightage : 23% 

All Questions for Topic 6.4 – Ventilation, Lung Structure, Pneumocytes, Mechanism of Breathing, Respiratory Muscles, Lung Disorders, Spirometry, Lung Capacity, Effect of Exercise, More Lung Disorders

Question

Which is an adaptation to increase rates of gas exchange in the lung?

    1. Small surface area

    2. Dry surface

    3. High vascularization

    4. Muscular alveoli

▶️Answer/Explanation

Ans: C

High vascularization is an adaptation to increase rates of gas exchange in the lung. The lungs are highly vascularized, which means they have a large number of blood vessels. This allows for efficient exchange of oxygen and carbon dioxide between the lungs and the bloodstream. The high vascularization of the lungs allows for a large surface area for gas exchange, which is necessary for efficient gas exchange to occur.

Question

Which conditions are correct for inspiration?

▶️Answer/Explanation

Markscheme

A

The external intercostal muscles are a group of muscles located between the ribs. They are responsible for elevating the ribcage during inhalation, which expands the chest cavity and allows air to flow into the lungs.

Question

What is the purpose of pulmonary surfactant?

A. Promotes capillary growth
B. Decreases surface tension
C. Adheres alveoli and capillaries
D. Stretches the inside surface of the alveoli

▶️Answer/Explanation

Markscheme

B

The purpose of pulmonary surfactant is to decrease surface tension within the alveoli of the lungs. This helps to prevent the collapse of the alveoli during exhalation, making it easier for air to flow in and out of the lungs. Therefore, the correct answer is B.

Question

The image shows a section of the human respiratory system. Which letter identifies a bronchiole?

▶️Answer/Explanation

Markscheme

D

D identifies a bronchiole. Bronchioles are approximately 1 mm or less in diameter and their walls consist of ciliated cuboidal epithelium and a layer of smooth muscle. Bronchioles divide into even smaller bronchioles, called terminal, which are 0.5 mm or less in diameter. The lower respiratory tract consists of the trachea (windpipe), bronchial tubes, and lungs. The bronchial tubes carry air into the lungs and branch into smaller and smaller bronchioles.

Question

What changes take place in the thorax during inhalation?

▶️Answer/Explanation

Markscheme

B

During inhalation, the thorax expands in several ways. The diaphragm, which is a muscle that separates the thoracic cavity from the abdominal cavity, contracts and moves downward. This increases the volume of the thoracic cavity, which decreases the pressure inside the lungs. The intercostal muscles, which are located between the ribs, also contract, lifting the ribcage and further increasing the volume of the thoracic cavity. This expansion of the thorax creates a pressure gradient that causes air to flow into the lungs, filling them with oxygen.

Question

The graph shows the concentration of the lipid lecithin in the amniotic fluid surrounding the fetus during normal gestation. This lipid is produced in the lungs of the fetus and acts as a surfactant.

What problem may occur in a baby born before 34 weeks gestation?

A. Type I pneumocytes do not produce sufficient surfactant for lungs to inflate.

B. There are no type II pneumocytes.

C. The alveolar walls stick together.

D. The alveoli are too large.

▶️Answer/Explanation

Ans:C

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