Answers – 8.1 Human Nutrition – Diet

Why this answer is correct:
Carbohydrates are the body’s main source of energy. They are broken down into glucose, which cells use for energy in activities like movement, breathing, and thinking. Building cells is the job of proteins, protecting organs is done by lipids, and fighting diseases is done by proteins (antibodies).

Why this answer is correct:
Scurvy is caused by a lack of vitamin C. Symptoms include bleeding gums, loose teeth, and poor wound healing. Rickets is caused by vitamin D or calcium deficiency. Anaemia is caused by iron deficiency. Diabetes is not a deficiency disease.

Why this answer is correct:
Iron is needed to make haemoglobin, which is the red pigment in red blood cells that carries oxygen around the body. Without enough iron, the body cannot make enough red blood cells, leading to anaemia.

Why this answer is correct:
Enzymes are made from proteins, not lipids. Stored fat does provide energy reserves, insulation (keeping you warm), and protection for organs. Lipids have many functions, but making enzymes is not one of them.

Why this answer is correct:
Meat, fish, and eggs are all animal products that are rich in protein. Rice, bread, and pasta contain mainly carbohydrates. Butter and oils are lipids. Citrus fruits contain mainly vitamin C and carbohydrates.

Why this answer is correct:
Rickets causes soft, bent bones (especially leg bones) and poor growth in children. It is caused by a deficiency of vitamin D or calcium. Scurvy affects gums and teeth. Anaemia causes tiredness and breathlessness. Obesity is not a deficiency disease.

Why this answer is correct:
Fibre cannot be digested by the human body, but it adds bulk to food and helps it move through the intestines. This prevents constipation and keeps the digestive system healthy. Fibre does not provide energy, is not stored, and is not used to build cells.

Why this answer is correct:
These are the symptoms of anaemia, which is caused by iron deficiency. Without enough iron, the body cannot make enough haemoglobin to carry oxygen in the blood. This causes tiredness, breathlessness, and pale skin.

Why this answer is correct:
Oily fish (like salmon and mackerel) and eggs are good sources of vitamin D. Oranges and lemons contain vitamin C. Bread and rice contain carbohydrates. Carrots and spinach contain other vitamins and minerals but not much vitamin D.

Why this answer is correct:
The human body is made up of about 70% water. Water is needed for all chemical reactions in the body, for transport of substances, for temperature control, and as the main component of blood and cells.

Why this answer is correct:
Lipids (fats and oils) provide more than twice as much energy per gram compared to carbohydrates or proteins. This is why the body stores excess energy as fat – it is the most efficient way to store energy.

Why this answer is correct:
Scurvy is caused by vitamin C deficiency. Symptoms include bleeding gums, loose teeth, and poor wound healing. Vitamin C is needed to make collagen, which holds cells together. Soft bones are a symptom of rickets. Tiredness is a symptom of anaemia.

Why this answer is correct:
Proteins are large molecules made up of chains of amino acids joined together. Carbohydrates are the main energy source, not proteins. Proteins can be found in plant foods like beans and nuts. Lipids (not proteins) are stored under the skin for insulation.

Why this answer is correct:
Athletes do lots of physical activity, which uses a lot of energy. Carbohydrates are the main source of energy, so athletes need more carbohydrates than less active people. While athletes also need protein and water, the question specifically asks about carbohydrates.

Why this answer is correct:
Dairy products (milk, cheese, yogurt) are excellent sources of calcium. Calcium is needed for strong bones and teeth. Bread, pasta, and rice provide carbohydrates. Chicken, fish, and eggs provide protein. Butter, oil, and nuts provide lipids.

Important: For each nutrient, any of the correct functions listed would be acceptable. You only need to give ONE main function for each.

Any two of the above foods are correct.

Why this is important: Vitamin D helps calcium be absorbed in the intestines. Without vitamin D, even if you eat calcium, your body cannot use it properly. This is why vitamin D deficiency causes rickets (soft bones).

Key point: A balanced diet is different for different people – it depends on age, activity level, sex, and health. The correct proportions vary from person to person.

Any two sensible comparisons are acceptable. The key is to identify that teenagers are growing and usually more active than elderly people.

Any two of these symptoms are correct.

Important: Rickets can be caused by EITHER vitamin D deficiency OR calcium deficiency (or both). These two nutrients work together to build strong bones.

This is why rickets used to be common in children who worked in factories during the Industrial Revolution – they spent all day indoors and never got sunlight.

Pregnant women often take iron supplements because it is difficult to get enough iron from food alone.

Historical fact: Scurvy was common among sailors on long voyages because they had no fresh fruit or vegetables. British sailors were called “limeys” because they ate limes to prevent scurvy. Vitamin C cannot be stored in the body, so you need to eat it regularly.

Any two of these functions are correct.

Example: Eating rice and beans together provides all the amino acids needed because they complement each other.

Why these symptoms occur: Iron is needed to make haemoglobin in red blood cells. Haemoglobin carries oxygen around the body. Without enough red blood cells, not enough oxygen reaches the muscles and organs, causing tiredness and breathlessness.

How it works: Fibre is like a brush that sweeps through the intestines. It absorbs water and makes the contents of the intestines soft and bulky, which makes them easier to push along.

Wholegrain foods are much better sources of fibre than white/refined foods.

Any two sensible comparisons are acceptable. The key point is that Meal 2 has more vitamins, fibre, and protein, but less fat.

Important concept: Eating the occasional burger and chips is fine, but eating it every day means the diet is not balanced. The teenager would be getting too much of some nutrients (lipids) and not enough of others (vitamins, fibre).