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CIE iGCSE Co-Ordinated Science B9.4 Blood Exam Style Questions Paper 3

CIE iGCSE Co-Ordinated Science Paper 3 - All Chapters

Question

(a) Fig. 1.1 shows the parts of a human tooth.
(i) State the names of the parts labelled A and B in Fig. 1.1.
(ii) State the type of digestion that teeth are responsible for.
(b) Cavities are holes in the teeth caused by poor care of teeth. A survey records the average number of cavities that 12-year-old school students have in one school. Every five years, the survey is repeated with another group of 12-year-olds in the same school. Fig. 1.2 shows a bar chart of the results.
(i) Calculate the percentage decrease in the average number of cavities between 1985 and 2015 in Fig. 1.2.
(ii) Suggest three reasons for the trend seen in Fig. 1.2.
(c) The mouth has a good supply of blood. List two main components of blood.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):

• Topic B7.3 — Digestion (Part (a))
• Topic B7.3 — Digestion / data interpretation skills (Part (b))
• Topic B9.4 — Blood (Part (c))

▶️ Answer/Explanation

(a)(i) A — enamel; B — pulp (cavity)

Label A points to the hard white outer covering of the crown, which is enamel.
Label B points to the soft central region containing nerves and blood vessels, which is the pulp (cavity).

(a)(ii) Mechanical (physical) digestion

Teeth break food into smaller pieces by a physical/mechanical action.
No chemical change to the food molecules occurs, so this is mechanical (physical) digestion.

(b)(i) Average number of cavities in 1985 = 4.6; in 2015 = 0.8; percentage decrease ≈ 83%

Percentage decrease is calculated using \(\text{percentage decrease} = \dfrac{\text{decrease in value}}{\text{original value}} \times 100\).
Decrease in value \(= 4.6 – 0.8 = 3.8\).
Percentage decrease \(= \dfrac{3.8}{4.6} \times 100 \approx 83\%\).

(b)(ii) Any three from: improved dental care/technology; reduced sugar consumption / more calcium in diet; better dental health education; fluoride added to water/toothpaste

Better access to dentists and modern dental treatments reduces cavity formation.
Lower sugar intake and improved diet reduce the substrate available for cavity-causing bacteria.
Increased public health education and fluoride use (in water or toothpaste) strengthen enamel and improve oral hygiene.

(c) Any two from: red blood cells; white blood cells; plasma; platelets

Blood is made up of four main components.
These are red blood cells, white blood cells, platelets, and plasma.
Any two of these components score full marks.

Question

(a) Fig. 10.1 is a diagram of the gas exchange system in humans.
State the name of the parts labelled A and B in Fig. 10.1.
(b) Table 10.1 compares the composition of two gases in inspired air and expired air.
(i) Calculate the difference between the percentage of gas X in inspired air compared to expired air in Table 10.1.
(ii) Describe the test for gas Y and state the positive result.
(iii) State the name of the chemical reaction that occurs in cells that requires gas X.
(c) The rate of breathing increases during physical activity. State one other change to the pattern of breathing during physical activity.
(d) Pulse rate also increases during physical activity to supply more blood to the muscles. White blood cells are one of the major components of blood.
(i) State two other major components of blood.
(ii) State two functions of white blood cells.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):

• Topic B11.1 — Gas exchange in humans (Parts (a), (b), (c))
• Topic B9.4 — Blood (Part (d))

▶️ Answer/Explanation

(a) A – trachea ; B – diaphragm

The trachea (A) is the airway that carries air from the throat down towards the lungs.
The diaphragm (B) is the sheet of muscle beneath the lungs that contracts and relaxes to help drive breathing movements.

(b)(i) 5%

Gas X (oxygen) makes up 21% of inspired air and 16% of expired air.
The difference is \( 21 – 16 = 5\% \).

(b)(ii) Test: bubble the gas through limewater; Positive result: the limewater turns cloudy

Gas Y is carbon dioxide, which is tested for using limewater (calcium hydroxide solution).
If carbon dioxide is present, the limewater turns from clear to cloudy (milky) due to the formation of insoluble calcium carbonate.

(b)(iii) (Aerobic) respiration

Gas X is oxygen, which is required by cells to carry out aerobic respiration.
During aerobic respiration, oxygen is used to break down glucose to release energy.

(c) Increased depth of breathing

As well as breathing faster during physical activity, a person also breathes more deeply.
This increases the volume of air exchanged with each breath, supplying more oxygen and removing more carbon dioxide.

(d)(i) Any two from: red blood cells; platelets; plasma

Besides white blood cells, blood contains red blood cells, platelets and plasma.
Each of these components has a different role in transport, clotting or carrying blood cells.

(d)(ii) Phagocytosis; antibody production

Some white blood cells (phagocytes) engulf and destroy pathogens by phagocytosis.
Other white blood cells (lymphocytes) produce antibodies that help to destroy or neutralise pathogens.

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