2024 Cambridge IGCSE Food and Nutrition (0648) 模拟试题及答案详解

(a) Functions of Vitamin D: assists in the absorption of calcium and phosphorus from the small intestine; essential for the formation and maintenance of strong bones and teeth. (b) Deficiency diseases: (i) rickets, (ii) osteomalacia. (c) Dietary sources: oily fish (such as salmon or mackerel), egg yolk, butter, cheese, cod liver oil, fortified milk, or fortified margarine.

(a) Award 1 mark for each correct function: absorption of calcium/phosphorus; bone/teeth mineralisation/formation. (Max 2 marks). (b) Award 1 mark for each correct deficiency: (i) rickets (1 mark), (ii) osteomalacia (1 mark). (c) Award 1 mark for each correct dietary source: oily fish, eggs, liver, butter, fortified spreads. (Max 2 marks).

(a) Lipase / pancreatic lipase. (b) Glycerol and fatty acids. (c) Lacteals are small lymph vessels located in the centre of each villus in the small intestine. They absorb reconstituted fats (fatty acids and glycerol that have recombined as fat droplets/chylomicrons) because these molecules are too large to pass directly into the blood capillaries. The fat is then transported via the lymphatic system before entering the bloodstream near the heart.

(a) Award 1 mark for lipase / pancreatic lipase. (b) Award 1 mark for glycerol, 1 mark for fatty acids. (c) Award 1 mark for identifying lacteals as lymph vessels in the villi; 1 mark for explaining that they absorb large, recombined fat molecules/chylomicrons; 1 mark for mentioning transport via the lymphatic system into the bloodstream. (Max 3 marks).

(a) Ovalbumin and vitellin (or mucin / livetin). (b) (i) Egg white protein coagulates, sets, and turns from translucent to opaque white at around 60 degrees Celsius. (ii) Egg yolk protein thickens and sets at around 65 degrees Celsius. (c) Eggs are easily digested and soft to chew; they contain high biological value protein for the repair of body tissues; they are a good source of iron to prevent anaemia; they contain Vitamin A for healthy eyesight and Vitamin D for bone health.

(a) Award 1 mark for each named protein (e.g., ovalbumin, vitellin, albumin, livetin) up to 2 marks. (b) Award 1 mark for explaining egg white coagulation (sets/turns opaque white at 60C) and 1 mark for egg yolk thickening/setting (at 65C-70C). (c) Award 1 mark for each valid nutritional reason: easily digested/chewed, rich in HBV protein for tissue repair, contains iron/Vit A/Vit D. (Max 2 marks).

(a) Iron. (b) Tiredness / fatigue, pale skin, lack of energy, breathlessness, headaches. (c) Combine plant sources of iron (non-haem iron) with foods rich in Vitamin C (e.g., citrus fruits, bell peppers); avoid drinking tea or coffee during meals as tannins inhibit iron absorption; consume fermented or sprouted plant foods to reduce phytate levels; include a small amount of animal-based protein (haem iron) in the same meal to enhance non-haem iron absorption.

(a) Award 1 mark for iron. (b) Award 1 mark for each correct symptom (fatigue, pale skin, lethargy, breathlessness) up to 2 marks. (c) Award 1 mark for each guideline (e.g. eat with vitamin C, avoid tea/tannins with meals, combine with meat/haem iron sources, reduce phytates) up to 3 marks.

(a) Convection is the transfer of heat through the movement of liquid or gas currents. The warmer, less dense parts rise, while the cooler, denser parts sink, creating a continuous convection current. (b) Boiling, steaming, baking, deep-fat frying. (c) To soften tough cellulose in vegetables and collagen fibres in meat; to prevent the food from drying out; to dissolve soluble nutrients into a sauce or gravy to make it palatable; to cook food gently without burning.

(a) Award 2 marks for a complete definition (1 mark for heat transfer through liquids/gases, 1 mark for movement of currents / hot rising and cold sinking). (b) Award 1 mark for each valid cooking method (boiling, steaming, baking, deep frying) up to 2 marks. (c) Award 1 mark for each valid reason (soften fibres/collagen, retain moisture, distribute heat evenly, prevent burning) up to 2 marks.

(a) Carbon dioxide (CO2). (b) Warmth (optimal temperature around 25 to 35 degrees Celsius), moisture (liquid like water or milk), food (sugar or starch from flour), and time. (c) The initial high heat causes the carbon dioxide gas and air bubbles in the dough to expand rapidly, causing the bread to rise (oven spring). Moisture in the dough turns to steam, which also contributes to the rising. Eventually, the yeast is destroyed by the high temperature, and the gluten coagulates, setting the structure of the loaf.

(a) Award 1 mark for carbon dioxide. (b) Award 1 mark for each condition (warmth, moisture, food/sugar, time) up to 3 marks. (c) Award 1 mark for explaining gas expansion/steam creation (rapid rise/oven spring), and 1 mark for explaining that yeast is killed and gluten coagulates to set the structure. (Max 2 marks).

(a) Salmonella, Escherichia coli (E. coli), Staphylococcus aureus, Listeria, Campylobacter. (b) 5 degrees Celsius to 63 degrees Celsius. (c) Use separate chopping boards and knives for raw meat and ready-to-eat foods like salads; wash hands thoroughly with warm soapy water after handling raw meat; clean and sanitise work surfaces between preparation tasks; keep raw foods covered and stored below cooked foods in the refrigerator.

(a) Award 1 mark for each correct bacterium up to 2 marks. (b) Award 1 mark for 5C to 63C. (c) Award 1 mark for each practice with explanation of how it prevents cross-contamination (e.g., separate boards for raw/cooked, hand washing after raw meat, correct fridge storage) up to 3 marks.

Detailed explanation of kitchen equipment safety, materials selection (stainless steel vs aluminium), and plastic bowl advantages as outlined in the marking scheme.

(a) [3 marks total, 1 mark per correct safety precaution] Accept: dry hands, turn off before removing beaters, cord safety, do not touch moving parts. (b) [4 marks total: 2 marks per explained advantage. 1 mark for stating the advantage, 1 mark for development/contrast with aluminium] Accept: non-reactive, durability/strength, hygienic/easy to clean. (c) [2 marks total, 1 mark per reason] Accept: lightweight, shatterproof/durable, non-reactive, quiet in use.

Detailed guide on the biological raising agent yeast: conditions required for growth, chemical/biological explanation of fermentation, and faults in yeast cookery resulting in a heavy texture.

(a) [3 marks total, 1 mark per condition] Accept: warmth, moisture, food/sugar, time. (b) [3 marks total] 1 mark for identifying yeast as a living organism/fungus or mentioning enzymes; 1 mark for fermentation/breakdown of sugar; 1 mark for products of anaerobic respiration being CO2 and alcohol. (c) [3 marks total, 1 mark per fault] Accept: yeast killed by high heat, yeast inactive due to cold, insufficient kneading/gluten development, over-kneading, insufficient proving, too much salt (inhibits yeast), too much flour/stiff dough.

Detailed study of hen's eggs: structural components, nutritional contribution of key nutrients for adolescent growth, and technical cooking properties (coagulation/binding) with a culinary example.

(a) [3 marks total, 1 mark per part] Accept: shell, yolk, white/albumen, chalazae, membrane, air space. (b) [3 marks total, 1 mark per nutritional benefit] Accept: HBV protein for growth/repair, iron for red blood cells/anaemia, Vitamin A for vision/skin, Vitamin D for bones/calcium, fat for energy, Vitamin B group for metabolism. (c) [3 marks total] 1 mark for explaining that egg protein coagulates/sets on heating; 1 mark for explaining that this binds/holds loose ingredients together; 1 mark for a correct named dish (e.g. burgers, rissoles, fishcakes, stuffing).

Comprehensive guidelines on food hygiene: understanding temperature controls (the danger zone), applying safe food handling methods during prep to avoid bacterial transfer, and identifying symptoms of foodborne illness.

(a) [2 marks total] 1 mark for explaining that bacteria multiply rapidly in this range; 1 mark for stating the range of 5C to 63C (or 4C to 60C). (b) [4 marks total, 1 mark per practice] Accept: separate colour-coded chopping boards, wash hands between tasks, separate utensils, store raw meat at the bottom of the fridge, sanitise worktops after raw prep. (c) [3 marks total, 1 mark per symptom] Accept: nausea, vomiting, diarrhoea, abdominal cramps, high temperature/fever, headache.

Overview of convenience foods: definition, assessment of frozen vegetables (peas) as a highly functional convenience item, and analysis of nutritional drawbacks of relying on ultra-processed canned foods.

(a) [1 mark] Accept: pre-prepared/processed food that saves time/effort/cooking skills. (b) [4 marks total, 1 mark per advantage] Accept: saves time, saves effort/labour, no waste/pods, long storage/shelf life, easy to portion, constant price, available year-round, nutrient retention due to quick freezing. (c) [4 marks total, 1 mark per explained disadvantage] Accept: high sodium/salt content, high free sugars, loss of heat-sensitive/water-soluble vitamins, low dietary fibre/NSP, high in saturated fats/fat content, presence of additives (preservatives/artificial colours).

An excellent response will detail both the biological/nutritional needs of older adults and the practical modifications required in meal planning to ensure these needs are met. Nutritional needs: Older adults require fewer calories because their metabolic rate slows and physical activity often declines. To avoid unhealthy weight gain, energy-dense foods high in empty calories (such as sugary snacks) should be limited. However, protein requirements remain high to preserve skeletal muscle mass (preventing sarcopenia) and promote healing. Adequate calcium and Vitamin D are vital because bone mass naturally decreases with age, raising the risk of osteoporosis; Vitamin D is particularly important as the skin becomes less efficient at synthesizing it from sunlight. Slower gastrointestinal motility makes constipation a common issue, which can be managed with high-fibre foods (whole grains, oats, fruits, vegetables) and at least 1.5 to 2 litres of water daily. Iron intake must be sustained to prevent fatigue and anaemia, aided by Vitamin C-rich foods. Vitamin B12 absorption declines in the stomach with age, so fortified foods or lean meats are necessary. Reducing sodium helps manage blood pressure, and reducing saturated fats lowers the risk of cardiovascular disease. Practical meal planning: Dental issues, such as missing teeth or dentures, require meals to have a soft consistency, such as stews, soups, mashed vegetables, or soft-cooked grains. Since appetite and stomach capacity may decrease, offering four to five small, nutrient-dense meals throughout the day is more effective than three large ones. Loss of taste and smell can make food seem bland; using aromatic herbs, garlic, onions, or lemon juice can make meals tasty without relying on salt. Brightly coloured meals stimulate visual appeal and appetite. For those with limited mobility or arthritis, pre-chopped ingredients, simple one-pot meals, or lightweight kitchen utensils can make cooking manageable. Lastly, cost-effective ingredients like lentils, canned sardines, and eggs are great for seniors on fixed retirement incomes.

Award 1 mark for each relevant discussed point, up to a maximum of 15 marks. Points must be divided across both nutritional needs and practical meal planning guidelines to access full marks. [Nutritional Needs - Max 8 marks]: - Energy: reduced need explained / lower BMR / lower activity level to prevent weight gain. - Protein: needed for repair / maintenance of muscle tissue / preventing sarcopenia. - Calcium: maintains strong bones / prevents osteoporosis. - Vitamin D: needed to absorb calcium / lack of outdoor activity. - Fibre / NSP: prevents constipation / stimulates peristalsis. - Water / Fluids: prevents dehydration / works with fibre / prevents constipation. - Iron: prevents anaemia / transports oxygen around the body. - Vitamin C: assists in the absorption of iron / immune health. - Vitamin B12: healthy nervous system / red blood cell formation. - Reduced salt / sodium: lowers risk of hypertension / stroke. - Reduced saturated fat: reduces risk of CHD / atherosclerosis. [Meal Planning Guidelines - Max 8 marks]: - Texture: soft / minced / easy-to-chew foods for those with dental decay / dentures. - Portion size: small / frequent meals for poor appetites / early satiety. - Flavouring: use of herbs / spices / lemon juice instead of salt due to loss of taste/smell buds. - Presentation: colorful / attractive dishes to stimulate failing appetite. - Ease of prep: simple dishes / pre-chopped food for those with arthritis / low mobility. - Cost: use of economical ingredients (eggs / canned fish) for fixed incomes / pensions. - Social aspects: eating with others / community meals to reduce depression-related malnutrition.