CIE iGCSE Co-Ordinated Science B18.3 Carbon cycle Exam Style Questions Paper 4
Question
(a) Fig. 4.1 is a diagram of the carbon cycle.
(i) Identify process E in Fig. 4.1.
▶️Answer/Explanation
Answer: fossilisation
Explanation: Process E represents the long-term storage of carbon in fossil fuels, which occurs through the fossilisation of dead organisms over millions of years.
(ii) Draw one arrow on Fig. 4.1 to represent the process of feeding.
▶️Answer/Explanation
Answer: An arrow drawn from “carbon in plants” to “carbon in animals.”
Explanation: Feeding represents the transfer of carbon from plants (producers) to animals (consumers) when animals consume plants or other animals.
(iii) State the balanced chemical equation for the process occurring at A in Fig. 4.1.
▶️Answer/Explanation
Answer: \(6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2\)
Explanation: Process A is photosynthesis, where carbon dioxide and water are converted into glucose and oxygen using sunlight energy.
(iv) Name process D in Fig. 4.1 and describe its effect on the atmosphere.
▶️Answer/Explanation
Answer:
- Name: combustion (of fossil fuels)
- Effect: increases concentration of carbon dioxide in the atmosphere
Explanation: Process D represents the burning of fossil fuels, which releases stored carbon back into the atmosphere as CO₂, contributing to the greenhouse effect.
(b) The element carbon is found in proteins.
(i) Name one disease caused by protein-energy malnutrition.
▶️Answer/Explanation
Answer: kwashiorkor or marasmus
Explanation: These are conditions resulting from insufficient protein intake, common in areas with food scarcity.
(ii) Name the smaller molecules that proteins are made from.
▶️Answer/Explanation
Answer: amino acids
Explanation: Proteins are polymers composed of chains of amino acids linked by peptide bonds.