A-LevelBiologyGas exchange9700/23 · Oct/Nov 2024 · Q112 Marks

Fig. 1.1 shows the structure of the human gas exchange system. [Figure 1.1]

(a)(i)Use the letters in Fig. 1.1 to identify the parts of the gas exchange system that contain cartilage.[1]
(a)(ii)Describe the role of cartilage in the gas exchange system.[2]
(a)(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. [Figure 1.2] [Figure 1.3] 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. [Table 1.1][4]
(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.[5]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

[1] B and C; Accept A, B and C if any other letters do not award the mark, ignore names
any two from:
keeps the (named) airway(s) open / prevents collapse of airways ; AW R bronchiole / alveoli e.g. to allow free flow of air into and out of, airways / lungs e.g. provides support (for the named airway(s)) I ‘provides strength'
allows flexibility; A described e.g. bending neck, swallowing food
AVP; e.g. (C-shaped incomplete) rings (in, B/ trachea) allow, lengthening / widening, during breathing in / inspiration / inhalation
region one mark for each letter – for 1.3 allow two or three letters if all are correct – ignore names
one mark for feature matched with function – feature and relationship to function must match if find a correct feature and its function in the last column – accept feature must be visible in Fig. 1.2 and Fig. 1.3 if gas (as in gas exchange) is not used, then answer must refer to oxygen and carbon dioxide
Fig. 1.2: G; air spaces; large surface area for, diffusion / gas exchange;
Fig. 1.2: G; walls are, thin / one cell thick A squamous epithelium R cell wall; short distance for, diffusion / gas exchange ;
Fig. 1.2: G; good blood supply / capillaries A capillary / red blood cells; for, diffusion / gas exchange or maintains steep concentration gradients or absorption / transport, of oxygen ;
Fig. 1.2: G; arteriole / venule R artery / vein; supply blood to capillaries / carry blood away from capillaries ;
Fig. 1.3: B; Accept C/A; goblet cells; secrete / produce / make, mucus ;
Fig. 1.3: B; Accept C/A; (many) cilia / ciliated epithelial cells / ciliated epithelium / ciliated cells; (cilia) move / AW, mucus (towards back of throat/AW);
Fig. 1.3: B; Accept C/A; ciliated epithelium; provides barrier to pathogens ;
any five from:
[1] sinoatrial node, releases / generates / produces, impulses / waves of excitation / waves of depolarisation / AW ; I 'signals' A SAN / SA node / pacemaker R nervous impulses
[1] impulses / AW, spreads to / across, walls / muscle of, (right) atrium; A atria
[1] right atrium contracts; A atrial systole if right atrium is given in answer, A pumps for contracts
[1] tricuspid / (right) atrioventricular, valve opens to allow blood to flow (from right atrium) into right ventricle ; R bicuspid valve / left atrioventricular valve
[1] atrioventricular node sends impulses down, septum / Purkyne tissue ; A to apex of heart / down Bundle of His A AVN/AV node
[1] atrioventricular node is responsible for / AW, a time delay ; A AVN/AV node
[1] right ventricle contracts ; A ventricular systole if right ventricle is given in answer, A pumps for contracts
[1] semi-lunar valve opens and blood flows into pulmonary artery / arteries; A pulmonary valve R aorta
[1] AVP; e.g. tricuspid / (right) atrioventricular, valve closes to stop, backflow / blood entering right atrium (only in correct context)