AQA GCSE Biology 8461: Key ideas – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover section 4.8, Key ideas, of the AQA GCSE Biology (8461) specification, for first teaching 2016 with exams from 2018 (version 1.0). The key ideas are embedded across the whole course, so these questions link topics that can appear on Paper 1 or Paper 2, at Foundation and Higher tier, every May/June. Question 2(b) uses Higher tier only content and is labelled.

Learn the ideas first in the study guide and the revision notes. The course hub is AQA GCSE Biology and the printable checklist lists every topic.

How to use this set. Most questions need facts from two or more topics. Before you write, name the key ideas involved (for example “structure and function” plus “genome”). Then write one linked step per mark, joining steps with “so” or “because”. Questions 8 and 11 are extended answers: plan the chain of processes first, then write it in order. Check each calculation by showing the working, not just the final value.

Questions

1.

(a) Complete the word equation: carbon dioxide + ________ → ________ + oxygen. [2] (b) State whether photosynthesis is endothermic or exothermic. [1]

2.

(a) Explain why amylase breaks down starch but does not break down protein. [2] (b) (Higher tier only) Explain how a mutation in the gene for an enzyme could stop the enzyme working. [3]

3. A student models a small animal as a cuboid 2 cm × 2 cm × 4 cm.

(a) Calculate its surface area to volume ratio. [3] (b) Explain why a much larger animal of the same shape needs a transport system and exchange surfaces. [2]

4.

(a) Put these in order of increasing size: organ, cell, organ system, tissue. [1] (b) Name one plant organ. [1] (c) Explain why xylem is described as a tissue. [1]

5. A piece of pondweed releases 42 bubbles of oxygen in 3 minutes.

(a) Calculate the rate of bubble production. [1] (b) Explain how the pondweed uses glucose from photosynthesis to make proteins. [3]

6. Compare aerobic respiration with anaerobic respiration in muscle cells. [4]

7. Explain the importance of sugars, amino acids, fatty acids and glycerol in metabolism. [4]

8. Describe how a carbon atom in carbon dioxide in the air can become part of a rabbit and then return to the air. [5]

9.

(a) How many DNA bases code for a protein of 150 amino acids? [1] (b) Define the term genome. [1] (c) Identical twins have the same genome, but one has a greater body mass. Explain this difference. [2]

10. A hospital tests bacteria from a ward. At first, 5 of 200 colonies are resistant to an antibiotic. After a year of heavy use of that antibiotic, 180 of 200 colonies are resistant.

(a) Calculate the percentage of resistant colonies at the start and after one year. [2] (b) Explain this change using the theory of natural selection. [4]

11. Explain why nearly all life on Earth depends on photosynthesis. [6]

12.

(a) Name the three domains in Carl Woese’s classification system. [1] (b) Explain why new classification systems have been proposed since Linnaeus. [2]

Answers

1. (a) water [1]; glucose [1] (b) Endothermic [1] Examiner insight: Symbols are only needed for recognition; a word equation must use words, and mixing words with symbols can lose the mark.

2. (a) The enzyme’s active site has a specific shape [1]; only starch fits (lock and key), protein does not [1]. (b) The mutation changes the base sequence, so the amino acid sequence changes [1]; the protein folds into a different shape [1]; the active site no longer fits the substrate [1]. Examiner insight: “The enzyme dies” earns nothing; each mark needs a step in the chain from DNA to shape to function.

3. (a) Surface area = 2 × (2×2 + 2×4 + 2×4) = 40 cm² [1]; volume = 2 × 2 × 4 = 16 cm³ [1]; ratio = 2.5 : 1 [1] (b) A larger animal has a smaller surface area to volume ratio [1], so diffusion across its surface alone is too slow to supply all its cells [1]. Examiner insight: Show surface area and volume separately; a bare ratio loses the method marks if it is wrong.

4. (a) cell → tissue → organ → organ system [1] (b) Leaf, root or stem [1] (c) It is a group of cells with a similar structure and function [1]. Examiner insight: The order mark needs all four in the correct sequence.

5. (a) 42 ÷ 3 = 14 bubbles per minute [1] (b) Glucose combines with nitrate ions [1] absorbed from the water [1] to make amino acids, which are joined to make proteins [1]. Examiner insight: Nitrate ions are the key mark – glucose alone contains no nitrogen for amino acids.

6. Aerobic uses oxygen; anaerobic does not [1]. Aerobic produces carbon dioxide and water; anaerobic in muscles produces lactic acid [1]. Aerobic transfers much more energy [1] because oxidation of glucose in anaerobic respiration is incomplete [1]. Examiner insight: “Compare” needs both processes in each point; describing only one side scores no marks for that point.

7. Sugars (glucose) are built into starch, glycogen and cellulose [1]. Amino acids are joined to make proteins [1]. One glycerol and three fatty acids form a lipid [1]. These molecules are also broken down, for example glucose in respiration, excess protein to urea [1]. Examiner insight: One mark per molecule type; lumping them into “they build things” earns one mark at most.

8. Carbon dioxide is absorbed by a plant for photosynthesis [1] and becomes part of glucose and other carbon compounds [1]. The rabbit eats the plant, and the carbon compounds are digested and absorbed [1]. Carbon returns to the air as carbon dioxide from the rabbit’s respiration [1], and when microorganisms decompose the rabbit’s waste or body and respire [1]. Examiner insight: Name the process at each transfer (photosynthesis, feeding, respiration, decomposition); arrows without process names do not score.

9. (a) 150 × 3 = 450 [1] (b) The entire genetic material of an organism [1]. (c) Their genes are the same, so the difference is environmental [1], for example diet or exercise [1]. Examiner insight: (c) needs both the conclusion “environmental” and a named example for two marks.

10. (a) Start: 5 ÷ 200 × 100 = 2.5 % [1]; after one year: 180 ÷ 200 × 100 = 90 % [1] (b) Mutations produced a few resistant bacteria (variation) [1]. The antibiotic killed non-resistant bacteria [1]. Resistant bacteria survived and reproduced [1], passing on resistance, so the proportion of the resistant strain rose [1]. Examiner insight: Do not say the antibiotic “caused” the mutation – resistance was already present; this error loses the first mark.

11. Green plants and algae use light to make glucose from carbon dioxide and water [1]. They are the producers at the start of every food chain [1], so all consumers depend on the biomass they make [1]. Photosynthesis releases oxygen [1], which organisms use in aerobic respiration [1]. Glucose is the fuel for respiration, which transfers the energy needed for life processes [1]. Other valid points for credit: glucose is converted to starch, cellulose, fats and proteins, so photosynthesis supplies the building materials of all biomass; and photosynthesis removes carbon dioxide from the air as part of the carbon cycle. Examiner insight: A 6-mark answer is marked on levels; linking food chains and oxygen/respiration in one logical chain reaches the top level.

12. (a) Archaea, bacteria, eukaryota [1] (b) Improved microscopes revealed more about internal structures [1]; chemical analysis of biochemical processes gave new evidence of relationships [1]. Examiner insight: One mark needs all three domain names; “prokaryotes” is not a domain.

Where marks are usually lost

• Saying enzymes are killed instead of denatured, or not mentioning the active site.
• Giving a surface area to volume ratio without showing area and volume.
• Leaving out nitrate ions when explaining protein synthesis in plants.
• Writing “energy is made” – energy is transferred.
• “Compare” answers that describe only one process.
• Suggesting antibiotics cause resistance mutations.
• Carbon cycle answers with no named processes.
• Not linking two ideas with “so” or “because” in a linked answer.
• Saying a larger organism has a larger surface area to volume ratio – the ratio gets smaller as size increases.
• Describing evolution as individuals changing in their lifetime rather than a population changing over generations.

Next steps

• Key ideas revision notes
• Key ideas study guide
• Ecology practice questions
• AQA GCSE Biology course hub
• Printable checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

AQA GCSE Biology (8461) specification, for first teaching 2016, exams from 2018, version 1.0, published by AQA – section 4.8 Key ideas.