Biological molecules — Paper 3 · IGCSE Sciences - Co-ordinated (Double) 0654

5 Fig. 5.1 shows a list of items that have been bought from a food shop. Shopping list • Bread • Butter • Fish • Melon • Pasta • Tomatoes • Water (bottled) Fig. 5.1 (a) Name one food on the shopping list in Fig. 5.1 that is a major source of fat, … protein, … vitamin C. … [3] (b) (i) State one reason why proteins are needed in our diet. … … [1] (ii) State the chemical elements contained in a protein. … [1] (iii) Name the smaller (basic) units that are produced during the digestion of protein. … [1] (c) Table 5.1 shows the different energy requirements for different people. Table 5.1 energy requirement per day / kJ male female 14 year old 12 000 9500 adult office worker 10 000 9000 athlete 13 500 12 000 (i) Suggest one reason for the difference in energy requirements between a male 14 year old and a male office worker. … … [1] (ii) Suggest one reason for the difference in energy requirements between a male athlete and a female athlete. … … [1]

8 marks

Mark scheme: 5(a) fat butter ; protein fish ; vitamin C melon / tomatoes ; 3 5(b)(i) growth / repair ; 1 5(b)(ii) carbon hydrogen oxygen nitrogen ; 1 5(b)(iii) amino acids ; 1 5(c)(i) (teenager) more active ; has a higher metabolic rate ; is still growing ; max 1 5(c)(ii) (female athlete) lower metabolic rate ; generally, smaller in size / mass ; max 1

This question in 0654/31 May/June 2017

4 The diagram in Fig. 4.1 shows a cross-section of human skin. hair shaft pore of sweat gland epidermis sebaceous gland dermis sweat gland subcutaneous tissue artery vein Fig. 4.1 (a) The skin has an important role in regulating the temperature of the body. (i) Describe two responses by the body when it gets too hot. 1 … 2 … [2] (ii) Describe two responses by the body when it gets too cold. 1 … 2 … [2] (b) The body is kept at a constant temperature of around 37 °C. This is the best temperature for enzyme activity. (i) State the function of enzymes. … [1] (ii) State one other factor that affects enzyme activity. … [1] (c) Enzymes are made of protein. List the chemical elements in a protein molecule. … [1]

7 marks

Mark scheme: 4(a)(i) sweating ; vasodilation / more blood flows (close) to the surface of the skin ; hair lies flat ; max 2 4(a)(ii) vasoconstriction / more blood flows (close) to internal organs / away from skin ; hair stands on end ; reduction in sweating ; max 2 4(b)(i) speed up reactions ; 1 4(b)(ii) pH / substrate concentration ; 1 4(c) carbon, hydrogen, oxygen, nitrogen ; 1

This question in 0654/32 May/June 2017

13 (a) In the human body digestion is required to break down large, insoluble food molecules into small, water‑soluble molecules that can be absorbed. (i) Complete Table 13.1 to describe the two types of digestion process that take place in the human body. Table 13.1 digestion process example of this process in the human body … enzymes in the stomach breaking food down mechanical digestion … [2] (ii) Describe the movement of the digested food molecules during absorption. … … [2] (b) (i) The boxes on the left show some nutrients. The boxes on the right contain the smaller units from which they are made. Draw a line from each nutrient to their correct smaller units. nutrient smaller units fats and oils amino acids proteins glucose starch glycerol and fatty acids [2] (ii) Draw a circle around all the elements that are present in fats. calcium carbon hydrogen magnesium oxygen sulfur [1] (c) Define the term balanced diet. … … … … [2]

9 marks

Mark scheme: 13(a)(i) digestion process example of this process in the human body chemical digestion enzymes in the stomach breaking food down mechanical digestion food chewed / ground by teeth owtte 2 13(a)(ii) (across wall of) small intestine; into the blood; 2 13(b)(i) nutrient smaller units fats and oils amino acids proteins glucose starch glycerol and fatty acids 1 or 2 correct; 3 correct; 2 13(b)(ii) carbon, hydrogen and oxygen circled; 1 13(c) (diet contains) all required nutrients; in sufficient / correct proportions; 2

This question in 0654/32 Oct/Nov 2018

7 (a) A student investigates the conditions needed for photosynthesis. He keeps similar plants in different conditions for two days and then tests the leaves for starch. Table 7.1 is a table for the results. Table 7.1 does the plant test conditions plant kept in photosynthesise? (3 / ✗) • carbon dioxide 1 • light • carbon dioxide 2 • no light • no carbon dioxide 3 • light • no carbon dioxide 4 • no light Complete Table 7.1 to predict the expected results. [1] (b) Describe the test for starch and the positive result. test … positive result … [2] (c) Oxygen produced during photosynthesis moves out of the plant cells. Explain in detail how oxygen moves out of plant cells. Use the word concentration in your answer. … … … … … [3] (d) Fig. 7.1 is a diagram of a plant cell. B C A D F E Fig. 7.1 (i) Identify the letter from Fig. 7.1 that shows where photosynthesis occurs. … [1] (ii) Name the part you have identified in (d)(i). … [1] (iii) Name two parts of plant cells that are also present in animal cells. 1 … 2 … [2] [Total: 10]

10 marks

Mark scheme: 7(a) test 19, test 2–4 X ; 1 7(b) iodine solution ; blue-black ; 2 7(c) ref to diffusion ; higher concentration of oxygen inside the cell / ORA ; oxygen moves down a concentration gradient / from high to low concentration ; across the cell membrane / cell wall ; max 3 3 7(d)(i) D ; 1 7(d)(ii) chloroplast ; 1 7(d)(iii) cell membrane ; nucleus ; cytoplasm ; max 2 2

This question in 0654/33 Oct/Nov 2019

4 (a) Huntington’s disease is an inherited disease which damages neurones in the brain. The disease usually develops between the ages of 30–50. • The allele for developing Huntington’s disease is dominant, H. • The allele for not developing Huntington’s disease is recessive, h. Fig. 4.1 shows the probability of the offspring of cross 1 developing Huntington’s disease. cross 1 hh × hh cross 2 Hh × hh h h H h h hh hh h … … h hh hh h … … probability of offspring developing probability of offspring developing Huntington’s disease: Huntington’s disease: = 0% = … Fig. 4.1 (i) Complete Fig. 4.1 to show the probability of the offspring of cross 2 developing Huntington’s disease. [2] (ii) Name the type of breeding cross 1 represents. … [1] (iii) Use the example of the inheritance of Huntington’s disease to state the heterozygous genotype. … [1] (b) Alleles are versions of genes. Genes are lengths of DNA that code for a protein. (i) Circle the four elements that are in a protein. carbon calcium hydrogen oxygen nitrogen water potassium [1] (ii) Describe how to test a substance for protein. Include the positive result. … … … [2] (iii) The boxes on the left show large molecules. The boxes on the right show small molecules. Draw four lines to link each large molecule with the small molecules they are made from. large molecules small molecules fats and oils amino acids glycogen fatty acids and glycerol protein glucose starch [3] [Total: 10]

10 marks

Mark scheme: 4(a)(i) correct offspring genotype ; Hh, Hh, hh, hh probability 50% ; 2 4(a)(ii) pure ; 1 4(a)(iii) Hh ; 1 4(b)(i) carbon, hydrogen, oxygen and nitrogen circled ; 1 4(b)(ii) add biuret solution ; if the sample contains protein it will turn purple ; 2 Question Answer Marks 4(b)(iii) ;;; 1 correct for 1 mark 2 or 3 correct for 2 marks all correct for 3 marks fats and oils amino acids glycogen fatty acids and glycogen protein glucose starch 3

This question in 0654/32 May/June 2020

4 (a) Huntington’s disease is an inherited disease which damages neurones in the brain. The disease usually develops between the ages of 30–50. • The allele for developing Huntington’s disease is dominant, H. • The allele for not developing Huntington’s disease is recessive, h. Fig. 4.1 shows the probability of the offspring of cross 1 developing Huntington’s disease. cross 1 hh × hh cross 2 Hh × hh h h H h h hh hh h … … h hh hh h … … probability of offspring developing probability of offspring developing Huntington’s disease: Huntington’s disease: = 0% = … Fig. 4.1 (i) Complete Fig. 4.1 to show the probability of the offspring of cross 2 developing Huntington’s disease. [2] (ii) Name the type of breeding cross 1 represents. … [1] (iii) Use the example of the inheritance of Huntington’s disease to state the heterozygous genotype. … [1] (b) Alleles are versions of genes. Genes are lengths of DNA that code for a protein. (i) Circle the four elements that are in a protein. carbon calcium hydrogen oxygen nitrogen water potassium [1] (ii) Describe how to test a substance for protein. Include the positive result. … … … [2] (iii) The boxes on the left show large molecules. The boxes on the right show small molecules. Draw four lines to link each large molecule with the small molecules they are made from. large molecules small molecules fats and oils amino acids glycogen fatty acids and glycerol protein glucose starch [3] [Total: 10]

10 marks

Mark scheme: 4(a)(i) correct offspring genotype ; Hh, Hh, hh, hh probability 50% ; 2 4(a)(ii) pure ; 1 4(a)(iii) Hh ; 1 4(b)(i) carbon, hydrogen, oxygen and nitrogen circled ; 1 4(b)(ii) add biuret solution ; if the sample contains protein it will turn purple ; 2 Question Answer Marks 4(b)(iii) ;;; 1 correct for 1 mark 2 or 3 correct for 2 marks all correct for 3 marks fats and oils amino acids glycogen fatty acids and glycogen protein glucose starch 3

This question in 0654/33 May/June 2020

1 (a) It is recommended that people eat a balanced diet. Place a tick (3) next to the sentence that best describes a balanced diet. A balanced diet contains all the required nutrients in the correct amounts. A balanced diet contains the correct amounts of carbohydrates. A balanced diet contains lots of fruit and vegetables. A balanced diet contains no fats or salt. [1] (b) The boxes on the left show some nutrients. The boxes on the right show why the nutrients are needed by the body. Draw lines to link each nutrient with why it is needed by the body. nutrient why it is needed carbohydrate for bones and teeth fats insulation protein main source of energy vitamin D used for growth and repair [3] (c) List the three chemical elements that make up carbohydrates. … [1] (d) Benedict’s solution can be used to test for the presence of one type of carbohydrate. Name the carbohydrate that Benedict’s solution is used to test for. … [1] (e) Name the component of the diet that prevents constipation. … [1] (f) Eating less sugar can help prevent tooth decay. Describe one other way of taking care of teeth. … … [1] (g) Circle the two processes that occur in the mouth. ingestion digestion egestion fertilisation photosynthesis pollination transpiration [2] [Total: 10]

10 marks

Mark scheme: 1(a) A diet containing all the required nutrients in the correct amounts ticked ; 1 1(b) carbohydrate for bones and teeth fats insulation protein main source of energy vitamin D used for growth and repair ;;; 3 1(c) carbon, hydrogen and oxygen ; 1 1(d) (reducing) sugar ; 1 1(e) fibre ; 1 1(f) regular brushing / AVP ; 1 1(g) ingestion circled ; digestion circled ; 2

This question in 0654/32 Feb/March 2021

10 (a) A student writes a definition of an enzyme. The definition is not correct. ‘Enzymes are fats that function as chemical catalysts.’ Circle the two words in the student’s definition that are not correct. [2] (b) Enzymes are used to break down large molecules into smaller molecules. Table 10.1 shows some large molecules and the smaller molecules they are made from. Complete Table 10.1. Table 10.1 large molecules smaller molecules 1. starch glucose 2. … amino acids … fats 1. fatty acids 2. … [3] (c) List the three chemical elements that make up fats. 1 … 2 … 3 … [1] (d) Fig. 10.1 is a graph showing the enzyme activity at different temperatures of four different enzymes, A, B, C and D. C D B enzyme A activity –10 0 10 20 30 40 50 60 70 80 90 100 110 temperature / °C Fig. 10.1 Table 10.2 shows average temperatures in different environments. Table 10.2 type of environment average temperature / °C hot springs 50 arctic sea –2 hydrothermal vent region 95 deep sea 2 volcano sediment 75 (i) Describe the effect of temperature on the enzyme activity of enzyme B. Use data to support your answer. … … … … [2] (ii) Use Fig. 10.1 and Table 10.2 to identify the enzyme, A, B, C or D, found in bacteria that can survive in: hydrothermal vent regions … arctic seas … the same environment as enzyme C … [3] [Total: 11]

11 marks

Mark scheme: 10(a) fats ; chemical ; 2 10(b) glycogen ; protein ; glycerol ; 3 10(c) carbon hydrogen and oxygen ; 1 10(d)(i) as temperature increases enzyme activity increases then decreases ; peak / optimum at 33 °C ; 2 10(d)(ii) D ; A ; D ; 3

This question in 0654/32 Oct/Nov 2021

4 (a) Different digestive enzymes work best at different pH values. The best pH for enzyme activity is called its optimum pH. Fig. 4.1 shows the optimum pH of five different digestive enzymes. 9 8 7 6 5 optimum pH 4 3 2 1 0 A B C D E enzyme Fig. 4.1 Use Fig. 4.1 to complete these sentences. The enzyme with the lowest optimum pH is enzyme … . The two enzymes with the same optimum pH are enzymes … and … . The enzyme that works best in neutral conditions is enzyme … . [3] (b) Name one factor, other than pH, that affects enzyme activity. … [1] (c) Complete this definition of an enzyme. Enzymes are proteins that function as … catalysts. [1] (d) Carbohydrate, protein and fat are made from chemical elements. Place ticks (3) in the boxes in Table 4.1 to show all the correct elements each substance is made from. Table 4.1 element substance carbon hydrogen oxygen nitrogen carbohydrate protein fat [3] (e) Starch is a carbohydrate. (i) State the name of the smaller molecules that starch is made from. … [1] (ii) Circle the name of one other carbohydrate. amino acid fatty acid glycogen oil [1] [Total: 10]

10 marks

Mark scheme: 4(a) B ; A and C ; E ; 3 4(b) temperature ; 1 4(c) biological ; 1 Question Answer Marks 4(d) element substance carbon hydrogen oxygen nitrogen carbohydrate    protein     fat    3 4(e)(i) glucose ; 1 4(e)(ii) glycogen circled ; 1

This question in 0654/32 May/June 2022

4 (a) Different digestive enzymes work best at different pH values. The best pH for enzyme activity is called its optimum pH. Fig. 4.1 shows the optimum pH of five different digestive enzymes. 9 8 7 6 5 optimum pH 4 3 2 1 0 A B C D E enzyme Fig. 4.1 Use Fig. 4.1 to complete these sentences. The enzyme with the lowest optimum pH is enzyme … . The two enzymes with the same optimum pH are enzymes … and … . The enzyme that works best in neutral conditions is enzyme … . [3] (b) Name one factor, other than pH, that affects enzyme activity. … [1] (c) Complete this definition of an enzyme. Enzymes are proteins that function as … catalysts. [1] (d) Carbohydrate, protein and fat are made from chemical elements. Place ticks (3) in the boxes in Table 4.1 to show all the correct elements each substance is made from. Table 4.1 element substance carbon hydrogen oxygen nitrogen carbohydrate protein fat [3] (e) Starch is a carbohydrate. (i) State the name of the smaller molecules that starch is made from. … [1] (ii) Circle the name of one other carbohydrate. amino acid fatty acid glycogen oil [1] [Total: 10]

10 marks

Mark scheme: 4(a) B ; A and C ; E ; 3 4(b) temperature ; 1 4(c) biological ; 1 Question Answer Marks 4(d) element substance carbon hydrogen oxygen nitrogen carbohydrate    protein     fat    3 4(e)(i) glucose ; 1 4(e)(ii) glycogen circled ; 1

This question in 0654/33 May/June 2022

1 (a) A person keeps a food diary for one day. They photograph everything that they eat and drink in the day. Fig. 1.1 shows an extract from the diary. Midday meal: chicken, rice, green beans, cucumber and onion salad Drink: Water Fig. 1.1 (i) Identify one food item from Fig. 1.1 that is a principal source of: carbohydrate … protein … vitamins … [3] (ii) State why it is important to drink water as part of a balanced diet. … … [1] (b) Rice is classified as a starch that provides a lot of fibre. (i) State the colour iodine solution turns when added to starch. … [1] (ii) Circle the component from which starch is made. amino acids fatty acids glucose glycerol glycogen [1] (iii) Describe the importance of fibre in the diet. … … [1] (c) Olive oil is a liquid fat used for cooking food. Tick (3) the boxes to show the three chemical elements present in all cooking oils. calcium carbon hydrogen iron magnesium oxygen [1] [Total: 8]

8 marks

Mark scheme: Question Answer Marks 1(a)(i) rice ; 3 chicken ; (green) beans / cucumber / onions / salad ; 1(a)(ii) as a solvent / any valid point ; 1 1(b)(i) blue-black ; 1 1(b)(ii) glucose circled ; 1 1(b)(iii) prevents constipation / keeps food moving through the gut ; 1 1(c) carbon, hydrogen and oxygen ticked ; 1

This question in 0654/31 Oct/Nov 2022

1 (a) A student investigates the germination of pea seeds. The student places pea seeds in test-tubes with different conditions and records whether the seeds germinate. Table 1.1 shows the conditions for each test-tube. Table 1.1 test-tube water present? oxygen present? A yes yes B yes no C no no D no yes (i) Predict in which test-tube the pea seeds will germinate. … [1] (ii) State one other requirement for germination that is not tested in Table 1.1. … [1] (b) After the seeds germinate, the plant photosynthesises. (i) Complete the sentence to define photosynthesis. Photosynthesis is the process by which plants manufacture … from raw materials using energy from … . [2] (ii) State the two raw materials needed for photosynthesis. 1 … 2 … [2] (c) Peas contain protein. State the name of the smaller molecules from which protein is made. … [1] [Total: 7]

7 marks

Mark scheme: Question Answer Marks 1(a)(i) A ; 1 1(a)(ii) suitable temperature ; 1 1(b)(i) carbohydrates ; 2 light ; 1(b)(ii) carbon dioxide ; 2 water ; 1(c) amino acids ; 1

This question in 0654/33 Oct/Nov 2022

7 (a) Horses are herbivores. Define the term herbivore. … … … [2] (b) Fig. 7.1 is a photograph of the lower jaw of a horse. X Y Fig. 7.1 (i) The dental pattern of a horse is similar to that of humans. Identify the type of teeth labelled X and Y in Fig. 7.1. X … Y … [2] (ii) Identify the type of teeth found in a human jaw but not present in the jaw shown in Fig. 7.1. … [1] (iii) State the name of the type of digestion that takes place using teeth. … [1] (c) The statements describe some processes that occur in the alimentary canal. Place ticks (✓) to show all the statements that describe the process of absorption. food molecules are broken down so they become soluble food molecules become part of cells food molecules cross the wall of the small intestine food molecules enter the blood food molecules are taken in through the mouth [2] (d) Complete these sentences about biological molecules. Choose words or phrases from the list. Each word or phrase may be used once, more than once or not at all. amino acids fatty acids glycerol glycogen starch Proteins are made from smaller molecules called … . Glucose is used to make two larger molecules called … and … . Iodine solution is used to test for the presence of … . [4] [Total: 12]

12 marks

Mark scheme: 7(a) animal that gets its energy ; 2 from eating plants / AW ; 7(b)(i) X – premolars ; 2 Y – incisors ; 7(b)(ii) canines ; 1 7(b)(iii) mechanical ; 1 7(c) 2 food molecules cross the wall of the small intestine  food molecules enter the blood  ;; 2 ticks and 2 correct = 2 marks 3 ticks and 2 correct = 1 mark otherwise 0 marks 7(d) amino acids ; 4 glycogen ; starch ; starch ;

This question in 0654/31 Oct/Nov 2023

7 (a) Enzymes are only active within a specific pH range. Table 7.1 shows the specific pH range for five different enzymes. Table 7.1 enzyme pH range enzyme is active A 1–5 B 5–9 C 7–12 D 2–3 E 10–12 Identify the enzyme(s) from Table 7.1 that are: only active in acidic conditions … active over the widest range of pH values … active at pH 8. … [3] (b) State one factor, other than pH, that affects enzyme activity. … [1] (c) Enzymes are proteins. Circle the elements that all enzymes contain. calcium carbon chlorine hydrogen magnesium nitrogen oxygen [1] (d) Table 7.2 lists some large nutrient molecules and the smaller molecules from which they are made. Complete Table 7.2. Table 7.2 large nutrient molecule smaller molecules that nutrients are made from fats and oils fatty acids and … proteins … 1. starch 2. … … [4] (e) Digested nutrients are absorbed by the body. Place ticks (3) in the boxes to show two correct statements about absorption. involves the breakdown of insoluble molecules to soluble molecules involves movement of digested food molecules into the blood involves movement of insoluble food molecules into cells occurs across the wall of the liver occurs across the wall of the intestine [2] [Total: 11]

11 marks

Mark scheme: 7(a) A and D ; 3 C ; B and C ; 7(b) temperature / AVP ; 1 7(c) carbon, hydrogen, oxygen, nitrogen circled ; 1 7(d) 4 large nutrient molecule smaller molecules that nutrients are made from fats and oils fatty acids and glycerol ; proteins amino acids ; 1. starch glucose ; 2. glycogen ; 7(e) 2 involves the breakdown of insoluble molecules to soluble molecules involves movement of digested food molecules into the blood  involves movement of insoluble food molecules into cells occurs across the wall of the liver occurs across the wall of the intestine  ;; 3 ticks and 2 correct = 1 mark 3 ticks and 1 correct = 0 marks 4 or more ticks = 0 marks

This question in 0654/33 Oct/Nov 2023

10 (a) Fig. 10.1 shows the activity of some bacterial enzymes at different temperatures. CC AA DD enzyme activity EE BB –10 0 10 20 30 40 50 60 70 80 90 100 110 temperature / °C Fig. 10.1 Complete the sentences to describe the results in Fig. 10.1. The only two enzymes active at 60 °C are enzymes … and … . The greatest activity for enzyme E is at … °C. The enzyme active over the greatest range of temperatures is enzyme … . [4] (b) State one factor, other than temperature, that affects enzyme activity. … [1] (c) Enzymes are proteins. Circle the elements that all proteins are made from. carbon calcium hydrogen oxygen nitrogen [1] (d) State the name of the solution used to test for the presence of protein. … [1] (e) The boxes on the left show some biological molecules. The boxes on the right show the smaller molecules they are made from. Draw lines to link each biological molecule to all the smaller molecules they are made from. amino acids fats and oils fatty acids glycogen glucose protein glycerol [3] [Total: 10]

10 marks

Mark scheme: 10(a) C ; D ; 95 (°C) ; C ; 4 10(b) pH / avp ; 1 10(c) carbon, hydrogen, oxygen and nitrogen all circled ; 1 Question Answer Marks 10(d) biuret ; 1 10(e) amino acids fats and oils fatty acids glycogen glucose protein glycerol ;;; 3

This question in 0654/31 May/June 2024

7 (a) A student investigates the effect of light on an aquatic plant. The student counts the number of bubbles of gas released in one minute by the aquatic plant kept in the light. The experiment is repeated with the aquatic plant kept in the dark. Table 7.1 shows the results. Table 7.1 environmental condition number of bubbles of gas released in one minute light 32 dark 0 (i) Complete the sentences to explain the results shown in Table 7.1. The aquatic plant releases more bubbles of … gas when kept in the light. This is because the process of … requires energy from light. This energy is used to react the raw materials … and … . This process takes place in plant cell structures called … . [4] (ii) State the name of the response that causes plants to grow towards light. … [1] (b) Fig. 7.1 is a photomicrograph of a cross‑section through a leaf. X Y Fig. 7.1 (i) State the name of the part labelled X in Fig. 7.1. … [1] (ii) State the names and functions of the two transport tissues contained in the part labelled Y in Fig. 7.1. name 1 … function … name 2 … function … [4] (c) Describe the importance of nitrate ions in the synthesis of proteins. … … … [1] [Total: 11]

11 marks

Mark scheme: 7(a)(i) oxygen ; photosynthesis ; carbon dioxide and water ; chloroplasts ; 4 7(a)(ii) phototropism ; 1 7(b)(i) (upper) epidermis ; 1 Question Answer Marks 7(b)(ii) xylem ; transports mineral ions / water or xylem is for support (of leaf) ; phloem ; transports dissolved sugars ; 4 7(c) nitrates are required to synthesise, amino acids (which make proteins) ; 1

This question in 0654/33 May/June 2024

1 (a) Euglena are single-celled organisms that have features of both animal and plant cells. Fig. 1.1 is a labelled diagram of a Euglena. eye spot (detects light) flagellum (spins to propel the cell) cytoplasm cell membrane contractile vacuole (removes excess water) chloroplast nucleus Fig. 1.1 (i) The parts labelled in Fig. 1.1 are responsible for different characteristics of living organisms. Identify the part responsible for: excretion … movement … nutrition … sensitivity. … [4] (ii) State the name of one other characteristic of living organisms. … … [1] (iii) State one part from Fig. 1.1 that Euglena have in common with plant cells but not with animal cells. … [1] (b) Euglena and animal cells do not have cell walls. State the function of the cell wall. … … … [1] (c) Cell walls are made from a type of carbohydrate called cellulose. Cellulose is made up of smaller molecules of glucose. (i) List the chemical elements in all carbohydrates. … … [1] (ii) Circle two other larger carbohydrate molecules made from glucose. fat glycerol glycogen oil protein starch [2] [Total: 10]

10 marks

Mark scheme: Question Answer Marks 1(a)(i) contractile vacuole ; 4 flagellum ; chloroplast ; eyespot ; 1(a)(ii) respiration / growth / reproduction ; 1 1(a)(iii) chloroplast ; 1 1(b) strengthen cell / AW ; 1 1(c)(i) carbon, hydrogen, oxygen ; 1 1(c)(ii) glycogen circled ; 2 starch circled ;

This question in 0654/31 Oct/Nov 2024

2 (a) The boxes on the left show different processes that occur in the human body. The boxes on the right show the descriptions of some of the processes. Draw one line from each process to its correct description. process description the uptake and use of nutrients by cells egestion the taking of substances, e.g. food and drink, into the body ingestion the removal of undigested food from the body as faeces digestion the movement of nutrients from the assimilation intestine into the blood the breakdown of food [4] (b) (i) Large biological molecules are made from smaller molecules. Complete the sentences about different biological molecules. Large protein molecules are made from smaller molecules called … . The elements in protein molecules are carbon, … , oxygen and … . Glycogen is a large molecule made from smaller molecules called … . [3] (ii) Reducing sugars are small biological molecules. State the name of the reagent used to test for reducing sugars. Give the observation for a positive result. reagent … observation for a positive result … … [2] [Total: 9]

9 marks

Mark scheme: 2(a) 4 ; ; ; ; 2(b)(i) amino acids ; 3 hydrogen (and) nitrogen ; glucose ; 2(b)(ii) add Benedict’s (and heat) ; 2 (brick) red / orange /yellow/ green ;

This question in 0654/32 Feb/March 2025

2 (a) (i) State all the elements found in the molecules of: protein … … glycogen. … … [2] (ii) State the names of the two different smaller molecules that make up a molecule of fat. … and … [2] (iii) State the test for protein and give the observation for a positive result. test … positive result … [2] (b) (i) Enzymes are proteins. Complete the sentence about enzymes. Enzymes are proteins that are involved in all … reactions, where they function as biological … . [2] (ii) Enzymes are affected by temperature. Place a tick (3) in the box next to the graph which shows the effect of temperature on enzyme activity. enzyme activity 0 0 temperature enzyme activity 0 0 temperature enzyme activity 0 0 temperature enzyme activity 0 0 temperature [1] [Total: 9]

9 marks

Mark scheme: 2(a)(i) (protein) = carbon, hydrogen, nitrogen, oxygen ; 2 (glycogen) = carbon, hydrogen, oxygen ; 2(a)(ii) glycerol ; 2 fatty acids ; 2(a)(iii) test – biuret ; 2 positive result – purple / violet ; 2(b)(i) metabolic ; 2 catalysts ; 2(b)(ii) 1

This question in 0654/31 Oct/Nov 2025

1 (a) Fig. 1.1 is a diagram of the alimentary canal and associated organs. E A B C D Fig. 1.1 (i) Identify the parts labelled A, C and E in Fig. 1.1. A … C … E … [3] (ii) Egestion occurs through structure D. Complete the sentence to describe egestion. Egestion is the removal of … food from the body as … . [2] (iii) State the name of a hormone produced by the part labelled B. … [1] (b) (i) Reducing sugars are absorbed into the blood from the alimentary canal. Describe the test for reducing sugar and the colour change observed for a positive result. test … colour change: starting colour … final colour … [3] (ii) Complete the word equation for photosynthesis: … + carbon dioxide … + … [2] (iii) The carbon dioxide needed for photosynthesis diffuses into the plant through the stomata. Place ticks (3) in two boxes to show the statements that correctly describe diffusion. Diffusion is described as the net movement of particles. Diffusion is the result of random movement of particles. Diffusion is the movement of particles from a lower to higher concentration. Diffusion is the movement of particles up a concentration gradient. In diffusion the particles always move through a partially permeable membrane. [2] [Total: 13]

13 marks

Mark scheme: Question Answer Marks 1(a)(i) A – stomach ; 3 C – large intestine ; E – gall bladder ; 1(a)(ii) undigested ; 2 faeces ; 1(a)(iii) insulin ; 1 1(b)(i) (heat with) Benedict’s (solution) ; 3 (starting colour) blue ; (final colour) red / orange / yellow / green ; 1(b)(ii) water + (carbon dioxide) → oxygen + glucose 2 1 mark left hand side correct 1 mark right hand side correct 1(b)(iii) 2 1 mark for each correct answer 3 boxes ticked – 2 correct – 1 mark 3 boxes ticked – 1 correct – 0 marks 4 boxes ticked – 0 marks

This question in 0654/32 Oct/Nov 2025