Nutrients and Their Functions
What is the main energy source for respiration in the human body?
Carbohydrates
What vitamin is needed for healthy connective tissues and wound healing, and whose deficiency causes scurvy?
Vitamin C
What is the name of the process of taking food into the body?
Ingestion
Which enzyme breaks down starch into maltose?
amylase
What test is used to detect starch in a food sample, and what is the positive result?
Iodine test; the solution turns blue-black if starch is present.
What nutrient is needed for growth and repair of tissues and for making enzymes and antibodies?
Proteins
What mineral is essential for healthy bones and teeth, blood clotting, and muscle function?
Calcium
What is the process called where large insoluble molecules are broken down into small soluble molecules?
Chemical digestion
Where in the digestive system is acid produced to help digestion and kill bacteria?
Stomach
How do you test for the presence of protein in a food sample, and what indicates a positive result?
Biuret test; add Biuret reagent to the sample. A positive result is a colour change from blue to purple.
What are the three main functions of fats in the human body?
Long-term energy storage, insulation and protection of organs, and absorption of fat-soluble vitamins
Why do growing children and pregnant women need more calcium in their diet than adult men who are not active?
Growing children need extra calcium for bone growth and development, and pregnant women need extra calcium for the developing baby's bones and teeth, as well as for their own health.
Why is mechanical digestion important in the digestive system?
It breaks food into smaller pieces, increasing surface area for enzyme action
What enzyme breaks down proteins into smaller peptides and amino acids?
Protease (e.g., pepsin, trypsin)
What test is used for fats (lipids), and what is the positive result?
Emulsion (ethanol) test: dissolve the sample in ethanol, then add water. A positive result is a cloudy white emulsion.
Why is dietary fibre important even though it is not digested by humans?
It helps food move through the digestive system and prevents constipation
What mineral is needed to make haemoglobin, and deficiency leads to anaemia?
Iron
What is the function of bile in digestion?
Bile neutralises stomach acid and emulsifies fats, increasing surface area for lipase
What enzyme breaks down fats (lipids) into fatty acids and glycerol?
Lipase
In a school experiment, how is the energy content of food roughly measured?
Burn a known mass of food under a test tube of water and measure the temperature rise of the water; larger temperature rise means more energy released.
Explain the difference between a balanced diet and a healthy diet.
A balanced diet provides all essential nutrients in the correct proportions; a healthy diet also considers the person’s age, activity level, and health needs
What is malnutrition, and how can it occur even when a person is overeating?
Malnutrition is an imbalance in nutrient intake; it can occur when someone eats too much of some nutrients (e.g., fats, sugars) but lacks others (e.g., vitamins, proteins)
Explain how the small intestine is adapted for efficient absorption of nutrients.
It has a large surface area (villi and microvilli), thin walls, and a rich blood supply
Describe the main functions of the large intestine in human nutrition.
Absorbs water and some minerals, forms and stores faeces, and hosts bacteria that produce some vitamins (e.g., vitamin K)
Why might different foods give different temperature rises in the simple burning experiment to measure energy content?
Different foods contain different amounts of energy per gram (different proportions of carbohydrates, fats, and proteins), so they release different amounts of heat when burned.