CIE iGCSE Co-Ordinated Science B11. Gas exchange in humans Exam Style Questions Paper 3
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.
A ……………………………………………………………………………………………………………………………..
B ……………………………………………………………………………………………………………………………..
(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.
test
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.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
(ii) State two functions of white blood cells.
1 ……………………………………………………………………………………………………………………….
▶Answer/Explanation
Ans:
10(a) A – trachea ;
B – diaphragm ;
10(b)(i) 5 (%) ;
10(b)(ii) limewater ;
cloudy ;
10(b)(iii) (aerobic) respiration ;
10(c) increased depth of breathing ;
10(d)(i) any two from:
red blood cells ;
platelets ;
plasma ;
10(d)(ii) phagocytosis ;
antibody production ;
Question
(a) Fig. 10.1 is a diagram of the gas exchange system in humans.
State the names of the parts labelled A, B and C in Fig. 10.1.
A ……………………………………………………………………………………………………………………………..
B ……………………………………………………………………………………………………………………………..
C ……………………………………………………………………………………………………………………………..
(b) Describe three ways the composition of expired air is different from inspired air.
1 ………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
2 ………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
3 ………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(c) Gases move across the gas exchange surface by diffusion.
Place ticks (✓) next to all the statements that correctly describe diffusion.
(d) Gas exchange also occurs in plants.
(i) State the name of the part of the leaf where water vapour exits.
…………………………………………………………………………………………………………………….
(ii) State the term used to describe when water evaporates and then diffuses out of a leaf.
…………………………………………………………………………………………………………………….
(iii) State two factors that increase the rate of water loss from a leaf.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 10(a) A – trachea ;
B – bronchus ;
C – alveoli ;
10(b) (expired air)
contains more carbon dioxide ;
contains less oxygen ;
contains more water vapour ;
;;
all correct = 2 marks
three ticks and two correct = 1 mark
otherwise = 0 marks
10(d)(i) stoma / stomata ;
10(d)(ii) transpiration ;
10(d)(iii) any two from:
increase in temperature ;
decrease in humidity ;
AVP ;
Question
(a) Fig. 1.1 is a diagram of the human gas exchange system.
(i) Identify the parts labelled A and B in Fig. 1.1.
▶️Answer/Explanation
A: Rib
B: Diaphragm
(ii) List three structures inspired air passes through on its way to the alveoli.
▶️Answer/Explanation
1: Nose/Mouth
2: Trachea
3: Bronchus/Bronchioles
(iii) Place a tick (✓) in the box to show the blood vessel that brings blood to the lungs.
▶️Answer/Explanation
Pulmonary Artery
(b) Expired air contains a higher percentage of carbon dioxide than inspired air.
(i) State one other way that the composition of expired air is different from inspired air.
▶️Answer/Explanation
Expired air contains less oxygen or more water vapor than inspired air.
(ii) State the test for carbon dioxide gas and give the observation for a positive result.
▶️Answer/Explanation
Test: Limewater
Observation: Limewater turns cloudy/milky.
(c) A student records their breathing rate while walking and while running. The results are shown in Fig. 1.2.
(i) State the breathing rate of the student while walking.
▶️Answer/Explanation
20 breaths per minute
(ii) The student repeats the investigation and records the breathing rate while at rest. Describe the expected changes to the pattern of breathing while at rest when compared to running.
▶️Answer/Explanation
The breathing rate will decrease, and the depth of breathing will also decrease when at rest compared to running.
Question
(a) Fig. 7.1 is a diagram of the gas exchange system in humans.
(i) Draw a label line and the name to identify a rib on Fig. 7.1.
(ii) Draw a label line and the name to identify the diaphragm on Fig. 7.1.
(b) Describe how inspired air is different from expired air.
(c) Name one of the main blood vessels that connects the lungs with the heart.
(d) Blood transports substances around the body.
(i) State the name of the part of the blood that transports oxygen.
(ii) State the name of the part of the blood that transports hormones.
(e) State the name of the hormone secreted in a ‘fight or flight’ situation.
▶️Answer/Explanation
(a) (i) and (ii): Rib and diaphragm should be correctly labelled on the diagram.
Detailed Solution: The rib and diaphragm are key structures in the gas exchange system. The rib is part of the ribcage that protects the lungs, while the diaphragm is a muscle that helps in breathing by contracting and relaxing to change the volume of the thoracic cavity.
(b) Inspired air contains more oxygen and less carbon dioxide compared to expired air. Expired air has more water vapor and carbon dioxide, and less oxygen.
Detailed Solution: Inspired air is the air we breathe in, which is rich in oxygen and has less carbon dioxide. Expired air is the air we breathe out, which has more carbon dioxide and water vapor due to the exchange of gases in the lungs.
(c) Pulmonary vein or pulmonary artery.
Detailed Solution: The pulmonary vein carries oxygenated blood from the lungs to the heart, while the pulmonary artery carries deoxygenated blood from the heart to the lungs.
(d) (i) Red blood cells.
Red blood cells contain hemoglobin, which binds to oxygen and transports it throughout the body.
(d) (ii) Plasma.
Plasma is the liquid component of blood that carries hormones, nutrients, and waste products.
(e) Adrenaline.
Adrenaline is a hormone secreted by the adrenal glands during stressful situations, preparing the body for a ‘fight or flight’ response by increasing heart rate, dilating airways, and redirecting blood flow to muscles.
Question
A scientist investigates the recovery time of an athlete and a non-athlete after exercise. Recovery time is the time taken for the pulse rate to return to normal after exercise.
The results are shown in Fig. 4.1.
(a)(i) State the pulse rate of the non-athlete at rest.
▶️Answer/Explanation
Answer: 72 bpm
Detailed Solution:
(a)(i) The pulse rate of the non-athlete at rest is 72 bpm. This is determined by observing the point on the graph where the non-athlete’s pulse rate is at its lowest before exercise begins.
(ii) State the length of recovery time for the athlete and the non-athlete.
▶️Answer/Explanation
Answer: Athlete: 3 minutes, Non-athlete: 7 minutes
Detailed Solution:
(a)(ii) The recovery time for the athlete is 3 minutes, and for the non-athlete, it is 7 minutes. This is calculated by measuring the time it takes for each individual’s pulse rate to return to their resting rate after exercise.
(iii) Calculate the difference in recovery times between the athlete and the non-athlete using your answers to (a)(ii).
▶️Answer/Explanation
Answer: 7 – 3 = 4 minutes
Detailed Solution:
(a)(iii) The difference in recovery times between the athlete and the non-athlete is 4 minutes. This is calculated by subtracting the athlete’s recovery time (3 minutes) from the non-athlete’s recovery time (7 minutes).
(iv) Describe the changes to the pattern of breathing of the non-athlete between 4 and 8 minutes.
▶️Answer/Explanation
Answer: The breathing rate would increase, and the breathing depth would increase.
Detailed Solution:
(a)(iv) Between 4 and 8 minutes, the non-athlete’s breathing rate and depth increase. This is because the body requires more oxygen to recover from the exercise and to remove the buildup of carbon dioxide.
(b) During exercise there is increased blood flow through the blood vessels. Fig. 4.2 is a photomicrograph of a cross‑section through an artery.
(i) State one piece of evidence from Fig. 4.2 that shows this blood vessel is an artery.
▶️Answer/Explanation
Answer: Thick wall
Detailed Solution:
(b)(i) The thick wall of the blood vessel is evidence that it is an artery. Arteries have thicker walls compared to veins to withstand the higher pressure of blood being pumped from the heart.
(ii) Name one component of blood visible in Fig. 4.2.
▶️Answer/Explanation
Answer: Red blood cell
Detailed Solution:
(b)(ii) One component of blood visible in Fig. 4.2 is the red blood cell. Red blood cells are responsible for carrying oxygen from the lungs to the rest of the body.
(c) The heart is responsible for pumping blood around the body.
(i) Name the structure that separates the right and the left sides of the heart.
▶️Answer/Explanation
Answer: Septum
Detailed Solution:
(c)(i) The structure that separates the right and left sides of the heart is called the septum. The septum ensures that oxygen-rich and oxygen-poor blood do not mix.
(ii) Name the type of tissue the walls of the heart are made from.
▶️Answer/Explanation
Answer: Muscular tissue
Detailed Solution:
(c)(ii) The walls of the heart are made from muscular tissue. This muscular tissue allows the heart to contract and pump blood throughout the body.
Question
(a) Fig. 7.1 is a diagram of the human gas exchange system.
(i) State the letters in Fig. 7.1 that identify the:
- bronchus
- diaphragm
- ribs
- trachea
▶️Answer/Explanation
Answer: The letters in Fig. 7.1 identify the following parts of the human gas exchange system:
- Bronchus: F
- Diaphragm: C
- Ribs: G
- Trachea: B
Explanation: The bronchus is a passage that leads air into the lungs, the diaphragm is a muscle that helps in breathing, the ribs protect the lungs, and the trachea is the windpipe that carries air to the bronchi.
(ii) Table 7.1 contains some statements. Place ticks (✓) next to the statements that correctly describe diffusion.
| Statement | ✓ |
|---|---|
| Diffusion occurs due to random movement of particles. | |
| Particles move up a concentration gradient. | |
| Substances move into cells by diffusion. | |
| The net movement of particles is from low to high concentration. | |
| Water does not diffuse into cells. |
▶️Answer/Explanation
Answer: The correct statements that describe diffusion are:
- Diffusion occurs due to random movement of particles.
- Substances move into cells by diffusion.
Explanation: Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration due to random motion. It is a passive process that allows substances to move into and out of cells.
(b) Inspired air contains more oxygen than expired air. Oxygen is used in the process of respiration.
(i) State two other ways that inspired air is different from expired air.
▶️Answer/Explanation
Answer: Two other ways that inspired air is different from expired air are:
- Inspired air contains less carbon dioxide than expired air.
- Inspired air contains less water vapor than expired air.
Explanation: During respiration, oxygen is used by the body, and carbon dioxide is produced as a waste product. Therefore, expired air has more carbon dioxide and water vapor compared to inspired air.
(ii) State why respiration enables protein synthesis to take place.
▶️Answer/Explanation
Answer: Respiration enables protein synthesis to take place because it releases energy.
Explanation: Protein synthesis is an energy-consuming process. The energy required for this process is provided by respiration, which breaks down glucose to release energy in the form of ATP.
(iii) State the substance that reacts with oxygen in aerobic respiration.
▶️Answer/Explanation
Answer: The substance that reacts with oxygen in aerobic respiration is glucose.
Explanation: In aerobic respiration, glucose is broken down in the presence of oxygen to produce carbon dioxide, water, and energy in the form of ATP.
Question
Fig. 11.1 shows the molecular structures of four carbon compounds, A, B, C and D.
(i) State which of the compounds are alkanes. Explain your answer.
▶️Answer/Explanation
Compounds B and D are alkanes. Alkanes are hydrocarbons that contain only single bonds between carbon atoms. In the molecular structures shown, compounds B and D have only single bonds between carbon atoms, which is characteristic of alkanes.
(ii) Fig. 11.2 shows two bottles, E and F, containing carbon compounds.
State which bottle contains a hydrocarbon. Explain your answer.
▶️Answer/Explanation
Bottle E contains a hydrocarbon. Hydrocarbons are compounds that contain only hydrogen and carbon atoms. The name “heptane” indicates that it is an alkane, which is a type of hydrocarbon. Bottle F contains heptanol, which is an alcohol and contains an oxygen atom, making it not a hydrocarbon.
(b) Ethene is made when ethanol vapour passes over a heated catalyst. Fig. 11.3 shows apparatus used to produce ethene from ethanol.
(i) Suggest the purpose of the catalyst in this reaction.
▶️Answer/Explanation
The catalyst increases the rate of the reaction by providing an alternative pathway with a lower activation energy. This allows the reaction to proceed faster at a given temperature.
(ii) The ethene passes through an orange solution which becomes colourless. Identify the orange solution.
▶️Answer/Explanation
The orange solution is aqueous bromine (bromine water). Ethene reacts with bromine water, causing it to decolorize as the bromine is used up in the reaction.
(iii) An ethene molecule is described as unsaturated. Explain why.
▶️Answer/Explanation
Ethene is described as unsaturated because it contains a double bond between the carbon atoms. Unsaturated compounds have at least one double or triple bond, which allows them to undergo addition reactions.
(c) Fig. 11.4 shows an ethanol burner. The balance measures the mass of the burner and ethanol.
(i) Complete the word equation for the complete combustion of ethanol.
▶️Answer/Explanation
ethanol + oxygen → carbon dioxide + water
(ii) Predict how the balance reading changes while the ethanol is burning. Explain your answer.
▶️Answer/Explanation
The balance reading decreases as the ethanol burns. This is because ethanol is being converted into carbon dioxide and water, which are gases and escape into the air, reducing the mass of the burner and ethanol.