Nutrition and Digestion
Nutrition and digestion is the topic covering the nutrients the body needs to stay healthy and how the digestive system breaks large food molecules down into small, soluble molecules that can be absorbed into the blood. It covers digestive organs, enzymes, food tests and energy calculations, building on knowledge of cells and their structures.
Method
- Learn the main nutrient groups and their function: carbohydrate, protein, fat, fibre, vitamins, minerals and water.
- Learn the digestive system organs in the order food passes through them, from mouth to small intestine.
- Understand enzyme action using the lock and key model, and match each enzyme to its substrate and product.
- Learn the food tests (iodine, Benedict's, Biuret, ethanol) and their positive results.
- Practise energy and nutrient calculations, such as the energy in a portion of food.
- Learn how the structure of villi in the small intestine is adapted for absorption.
Worked example
A packet of granola bars shows an energy value of 340 kJ per 100g. A pupil eats a 220g portion. Calculate the energy, in kJ, in the portion. Give your answer to 3 significant figures.
- Note that the energy value is given per 100g: 340 kJ per 100g.
- Scale this to the actual mass eaten: 340 x (220/100).
- Simplify the fraction: 220/100 = 2.2, so the calculation becomes 340 x 2.2.
- Calculate: 340 x 2.2 = 748.
- State the final answer to 3 significant figures: 748 kJ.
Practice questions
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Q1Which nutrient is the body's main source of quick energy?Show answer
Answer: Carbohydrate
Q2Name the digestive organ where mechanical digestion begins and saliva is added to food.Show answer
Answer: Mouth
Q3State the product formed when protease breaks down protein.Show answer
Answer: Amino acids
Q4State one function of bile in digestion.Show answer
Answer: It emulsifies fats into smaller droplets, increasing the surface area for lipase to act on.
Q5A cereal bar contains 180 kJ per 100g. Calculate the energy in a 40g bar.Show answer
Answer: 72 kJ (180 x 40/100 = 72)
Q6A pupil's daily energy intake is 9200 kJ and their daily energy use is 8600 kJ. Calculate their daily energy balance and state whether it is a surplus or a deficit.Show answer
Answer: 600 kJ surplus (9200 - 8600 = 600)
Exam-style questions
Written in the style of a KS3 Science exam paper, with a full mark scheme.
State the function of protein and the function of vitamin C in the human diet.
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A student investigates the effect of temperature on the rate of amylase breaking down starch, using the iodine test. State two variables that should be controlled in this investigation, other than temperature. Explain why the student should test a fresh drop of the mixture with iodine every 30 seconds, rather than adding iodine directly to the reaction mixture.
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Describe how a meal containing carbohydrate, protein and fat is digested and absorbed in the human body, referring to specific organs, enzymes and the process of absorption.
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Free printable worksheet
Want more practice on paper? Download the nutrition and digestion worksheet pack - 13 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
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