Home / A level Biology 7.1 Structure of transport tissues – Exam style question – Paper 2

A level Biology 7.1 Structure of transport tissues – Exam style question – Paper 2

A level Biology Paper 2 - All Chapters
Question

Fig. 1.1 shows the structure of the human gas exchange system.

(a) (i) Use the letters in Fig. 1.1 to identify the parts of the gas exchange system that contain cartilage.

(ii) Describe the role of cartilage in the gas exchange system.

(iii) Microscope slides were prepared from two regions of the gas exchange system. Fig. 1.2 and Fig. 1.3 are photomicrographs of the two slides.

Complete Table 1.1.

  • Use the letters from Fig. 1.1 to identify the regions of the gas exchange system from which the two slides were prepared.
  • Identify one feature visible in Fig. 1.2 and one feature visible in Fig. 1.3.
  • State one way in which each feature relates to its function.
Fig.region of the gas exchange system (A, B, C, D, E, F or G)one visible featureone way in which the feature relates to its function
1.2   
1.3   

(b) There is a regular and efficient supply of blood from the heart to the lungs. Describe the sequence of events that occurs in the heart to make sure that there is a regular and efficient supply of blood to the lungs.

▶️ Answer/Explanation
Solution

(a)(i) B and C

Explanation: In the human gas exchange system, cartilage is present in the trachea (B) and bronchi (C). These structures need cartilage to maintain their shape and prevent collapse during breathing.

(a)(ii) Any two from:

  • Keeps the airways open/prevents collapse of airways
  • Allows flexibility (especially important in the trachea during swallowing)
  • Provides structural support to maintain airway patency

Detailed Explanation: Cartilage plays crucial roles in the respiratory system. In the trachea and bronchi, the C-shaped cartilage rings prevent these tubes from collapsing during inhalation when air pressure decreases. The incomplete rings at the back allow the esophagus to expand during swallowing. Cartilage also provides flexibility, enabling the neck to bend without obstructing airflow.

(a)(iii)

Detailed Explanation: Fig. 1.2 shows alveoli (G) with their characteristic air spaces that provide a massive surface area for efficient gas exchange. The thin walls (one cell thick) allow rapid diffusion of oxygen and carbon dioxide. Fig. 1.3 shows the trachea (B) with ciliated epithelial cells. The cilia beat in coordinated waves to move mucus and trapped particles upward, protecting the lungs from infection and debris.

(b) Any five from:

  1. Sinoatrial node (SAN) generates electrical impulses
  2. Impulses spread across atrial walls causing atrial contraction
  3. Tricuspid valve opens allowing blood into right ventricle
  4. Atrioventricular node (AVN) delays impulse briefly
  5. Impulse travels down Bundle of His to ventricle apex
  6. Right ventricle contracts, pumping blood into pulmonary artery
  7. Pulmonary valve prevents backflow into ventricle

Detailed Explanation: The sequence begins with the sinoatrial node (the heart’s natural pacemaker) generating electrical impulses. These impulses cause the atria to contract, pushing blood through the open tricuspid valve into the right ventricle. After a brief delay at the AV node (allowing complete ventricular filling), the impulse travels down specialized conduction pathways to the ventricle walls, causing coordinated contraction. This forces blood through the pulmonary valve into the pulmonary arteries toward the lungs. The valves ensure one-way flow, while the coordinated timing maximizes pumping efficiency.

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