Edexcel International GCSE Biology 4BI1: Level of organisation and biological molecules – 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 sub-topics 2(a) Level of organisation (point 2.1) and 2(c) Biological molecules (points 2.7–2.14B) of the Pearson Edexcel International GCSE Biology (4BI1) specification, Issue 3, for the June and November series examined under Issue 3. The course is untiered and a calculator may be used on both papers. Question 9 tests the bold B statement 2.14B and is labelled “Paper 2 only”.

Learn the content first in the study guide and the revision notes. The questions here are different from those in the topic-level cell structure practice set, so you can use both. The course hub is Edexcel IGCSE Biology and the printable checklist lists every point.

Questions

1. State the level of organisation of each of these structures.

(a) A chloroplast [1] (b) The layer of ciliated epithelium lining the trachea [1] (c) A kidney [1]

2. A student writes: “The small intestine is a tissue because it is made of cells.” Explain why the student is wrong. [2]

3. A sample of a biological molecule is analysed. It contains carbon, hydrogen, oxygen, nitrogen and sulfur.

(a) Identify the type of biological molecule. [1] (b) Give a reason why it cannot be a lipid. [1]

4. Starch and glycogen are both storage carbohydrates.

(a) State the smaller units that both molecules are made from. [1] (b) Give one difference between starch and glycogen in where they are found. [1] (c) Describe the structure of a lipid molecule in terms of its smaller units. [1]

5. A student tests four solutions, A to D.

Solution	Benedict’s test	Iodine test	Biuret test	Emulsion test
A	Brick-red	Orange-brown	Blue	Clear
B	Blue	Blue-black	Blue	Clear
C	Blue	Orange-brown	Purple	Cloudy white
D	Blue	Orange-brown	Blue	Clear

(a) State the biological molecule or molecules present in A, B and C. [3] (b) The student concludes that D contains no sugar. D is a sucrose solution. Explain why the student’s conclusion is not valid. [2]

6. Describe how you would test a sample of crushed peanut for fat. Include one safety precaution. [3]

7. Amylase catalyses the breakdown of starch.

(a) Explain what is meant by the statement that amylase is a biological catalyst. [2] (b) Explain why amylase does not catalyse the breakdown of protein. [2]

8. A student investigates the effect of temperature on amylase. She records the time for all the starch to be digested, using iodine solution on a spotting tile. Each temperature is repeated three times.

Temperature (°C)	15	25	35	45	55
Mean time (s)	400	see (a)	80	100	500

(a) The three times at 25 °C were 196 s, 204 s and 290 s. Calculate the mean time at 25 °C, leaving out the anomalous result. [2] (b) Calculate the rate of reaction at 35 °C. Use the formula rate = 1 / time and give the unit. [2] (c) Calculate how many times faster the reaction is at 35 °C than at 15 °C. [1] (d) Explain why the rate at 55 °C is much lower than at 35 °C. [3] (e) State one variable the student should control, other than the volume of amylase. [1]

9. (Paper 2 only) A student measures the rate of an enzyme-catalysed reaction at four pH values.

pH	3	5	7	9
Rate (s⁻¹)	0.002	0.008	0.020	0.005

(a) Calculate the rate at pH 5 as a percentage of the rate at pH 7. [2] (b) Describe a method the student could use to investigate the effect of pH on the activity of amylase. [5]

10. Enzyme P has an optimum pH of 2. Enzyme Q has an optimum pH of 7. Both are found in the human digestive system.

(a) Suggest which enzyme works in the stomach. Give a reason. [1] (b) Explain why enzyme P has very little activity at pH 7. [2]

11. Two tubes are set up at 37 °C. Tube X contains starch solution and amylase. Tube Y contains starch solution and amylase that had been boiled and then cooled to 37 °C. After 10 minutes both tubes are tested.

Tube	Iodine test	Benedict’s test
X	Orange-brown	Orange
Y	Blue-black	Blue

(a) Explain the results for tube X. [2] (b) Explain the results for tube Y. [2] (c) In a separate experiment, the starch concentration in a tube falls from 2.0 g/dm³ to 0.5 g/dm³. Calculate the percentage of the starch that has been digested. [2]

Answers

1. (a) Organelle [1] (b) Tissue [1] (c) Organ [1] Examiner insight: One word per part is enough; adding “a group of cells” to (b) is fine, but “cell” for (b) scores zero because epithelium is many similar cells.

2. The small intestine contains several different tissues, such as muscle and epithelium [1]; a group of different tissues working together is an organ, not a tissue [1] Examiner insight: “It is made of cells” is true of every level above the cell, so the mark needs the word “different” or named tissues.

3. (a) Protein [1] (b) Lipids contain only carbon, hydrogen and oxygen, so a molecule with nitrogen cannot be a lipid [1] Examiner insight: Naming nitrogen as the deciding element is what earns (b); “it has more elements” is too vague.

4. (a) Glucose (simple sugar) [1] (b) Starch is stored in plants; glycogen is stored in animals (and fungi) [1] (c) Glycerol joined to fatty acids (usually three) [1] Examiner insight: Both units are needed in (c); “fatty acids” alone is incomplete and loses the mark.

5. (a) A: glucose [1]; B: starch [1]; C: protein and fat [1] (b) Benedict’s solution does not give a positive result with sucrose [1]; so a blue Benedict’s result does not show that no sugar is present – the student has not tested for sucrose [1] Examiner insight: In (a), C needs both molecules for the mark; giving only one of protein or fat scores zero for C.

6. Shake the crushed peanut with ethanol, then pour the ethanol into a tube of water [1]; a cloudy white emulsion shows fat is present [1]; keep ethanol away from flames because it is flammable [1] Examiner insight: The colour change must be stated as “cloudy” or “milky white emulsion”; “it changes colour” earns nothing.

7. (a) It speeds up the breakdown of starch [1]; without being used up or changed, and it is a protein made by living cells [1] (b) The active site of amylase has a shape complementary only to starch [1]; protein molecules do not fit the active site, so no enzyme-substrate complex forms [1] Examiner insight: (b) needs “active site” and “shape”; “amylase only works on starch” restates the question and gains no credit.

8. (a) (196 + 204) ÷ 2 [1] = 200 s [1] (b) 1 ÷ 80 [1] = 0.0125 s⁻¹ [1] (c) 400 ÷ 80 = 5 times faster [1] (d) At 55 °C the bonds holding the amylase in shape break [1]; the active site changes shape, so the enzyme is denatured [1]; starch no longer fits the active site, so fewer enzyme-substrate complexes form [1] (e) Any one: pH (using a buffer); concentration or volume of starch solution; concentration of amylase; time between samples [1] Examiner insight: Including 290 s in the mean in (a) loses the answer mark, and in (b) the unit s⁻¹ is needed for the second mark.

9. (a) 0.008 ÷ 0.020 × 100 [1] = 40% [1] (b) Add a buffer solution of a set pH to starch solution and amylase [1]; keep all tubes in the same water bath at one temperature [1]; mix and take one drop every 30 s onto iodine on a spotting tile [1]; record the time when the iodine stays orange-brown [1]; repeat for a range of pH values (for example 4 to 9), repeating each and calculating a mean [1] Examiner insight: A method that varies pH but never states that temperature is kept constant caps the plan, because temperature becomes an uncontrolled variable.

10. (a) P, because the stomach contains acid, so its pH is low [1] (b) At pH 7 the active site of P changes shape (is altered) [1]; so the substrate no longer fits and few enzyme-substrate complexes form [1] Examiner insight: (a) needs the reason; naming P without linking it to the acidic stomach earns nothing.

11. (a) No starch remains, because the amylase has broken it down [1]; into sugar, which gives a positive Benedict’s result [1] (b) Boiling denatured the amylase, changing the shape of its active site [1]; so starch was not broken down and no sugar was produced [1] (c) (2.0 − 0.5) ÷ 2.0 × 100 [1] = 75% [1] Examiner insight: In (b), cooling back to 37 °C does not restore the enzyme; an answer that says the amylase “recovers” contradicts the denaturation mark.

Where marks are usually lost

• Calling an organ “a group of cells” rather than “a group of different tissues”.
• Naming a single cell when the question asks for a tissue.
• Giving only one of the two units of a lipid.
• Stating a positive food test result without the starting colour when asked to “describe the change”.
• Treating a negative Benedict’s test as proof that no sugar of any kind is present.
• Saying an enzyme is “killed”, or saying the substrate does not fit without saying the active site changed shape.
• Including an anomalous repeat in a mean.
• Leaving off the unit (s⁻¹) on a rate, or dividing the wrong way in a percentage.
• In the pH practical (Paper 2 only), forgetting that temperature must now be controlled.

Next steps

• Recap with the revision notes.
• Reread any weak section in the study guide.
• Try the topic-level cell structure practice set.
• Browse other topics on the Edexcel IGCSE Biology hub.
• Track coverage with the printable checklist.
• Try all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

Pearson Edexcel International GCSE in Biology (4BI1) specification, Issue 3, first examination June 2019, Pearson Education Limited – Topic 2, Structures and functions in living organisms: sub-topics (a) Level of organisation and (c) Biological molecules.