CIE iGCSE Co-Ordinated Science B1.1 Characteristics of living organisms Exam Style Questions Paper 3
Question
excretion
movement
nutrition
sensitivity
State the function of the cell wall.
(ii) Circle two other larger carbohydrate molecules made from glucose.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B1.1 — Characteristics of living organisms (Parts (a)(i), (a)(ii))
• Topic B2.1 — Cell structure (Parts (a)(iii), (b))
• Topic B4.1 — Biological molecules (Part (c))
▶️ Answer/Explanation
(a)(i)
Excretion → contractile vacuole
The contractile vacuole removes excess water (a waste product), which is the process of excretion in Euglena.
Movement → flagellum
The flagellum spins to propel the cell, enabling movement.
Nutrition → chloroplast
The chloroplast carries out photosynthesis, allowing Euglena to manufacture its own food (nutrition).
Sensitivity → eye spot
The eye spot detects light, enabling the organism to respond to its environment (sensitivity).
(a)(ii)
Any one of: respiration / growth / reproduction
These are all recognised characteristics of living organisms not directly covered by the parts shown in Fig. 1.1.
Each characteristic reflects a fundamental life process shared by all living things.
(a)(iii)
Chloroplast
Chloroplasts are present in plant cells (for photosynthesis) but are absent in animal cells.
Euglena possesses chloroplasts, which is a feature shared with plant cells only.
(b)
The cell wall strengthens (supports / provides rigidity to) the cell.
It prevents the cell from bursting when water enters by osmosis, maintaining cell shape.
This structural support is why plant cells maintain a firm, regular shape unlike animal cells.
(c)(i)
Carbon, hydrogen, oxygen
All carbohydrates are composed exclusively of these three chemical elements.
The general formula for carbohydrates reflects this composition: \( \text{C}_x(\text{H}_2\text{O})_y \).
(c)(ii)
Glycogen and starch (both circled)
Both glycogen and starch are polysaccharides — large carbohydrate molecules built from many glucose units joined together.
Fat, glycerol, oil, and protein are not carbohydrates made from glucose monomers.
Question
• the part that supports the cell
• all the parts that are also found in animal cells.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B2.1 — Cell structure (Parts (a)(i), (a)(ii), (a)(iii))
• Topic B6.1 — Photosynthesis (Parts (b)(i), (b)(ii), (b)(iii))
• Topic B1.1 — Characteristics of living organisms (Part (c))
▶️ Answer/Explanation
(a)(i) Part where aerobic respiration takes place: D
Mitochondria (labelled D) are the organelles responsible for aerobic respiration, where glucose is broken down to release energy in the presence of oxygen.
Part that supports the cell: A or B
The cell wall (A) provides structural support to the plant cell. The vacuole (B) also helps maintain turgidity and support by exerting internal pressure on the cell wall.
All parts found in animal cells: D, E, F and G
Animal cells contain mitochondria (D), ribosomes (E), nucleus (F) and cell membrane (G). They do not have a cell wall, chloroplasts or a permanent large vacuole.
(a)(ii) Two ways bacterial cells differ from plant cells:
1. Bacterial cells have no nucleus (their genetic material is not enclosed in a membrane-bound nucleus).
2. Bacterial cells have no chloroplasts (they do not carry out photosynthesis).
Other acceptable differences: no mitochondria, no vacuole, or presence of a cell wall made of peptidoglycan rather than cellulose.
(a)(iii) Part labelled C: chloroplast
Chloroplasts are the organelles that contain chlorophyll and are the site of photosynthesis in plant cells.
(b)(i) Green pigment: chlorophyll
Chlorophyll is the green pigment found in chloroplasts that absorbs light energy for photosynthesis.
(b)(ii) Word equation for photosynthesis:
Carbon dioxide + Water \(\rightarrow\) Glucose + Oxygen
This equation shows the reactants (carbon dioxide and water) and products (glucose and oxygen) of photosynthesis, which occurs in the presence of light and chlorophyll.
(b)(iii) Photosynthesis is the process by which plants synthesise carbohydrates from raw materials using light energy.
Light energy is absorbed by chlorophyll and converted into chemical energy in the form of glucose.
(c) Two other characteristics of living organisms:
1. Movement – an action by an organism or part of an organism causing a change of position or place.
2. Respiration – the chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
Other acceptable answers: sensitivity, growth, reproduction, excretion.